[PATCH] contrib/xml2: xslt_process() should report XSLT-related error details

From cc5be302aa4305403b8131f6c22c39e4dfb75bd1 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Thu, 17 Apr 2025 13:15:48 +0300
Subject: [PATCH] contrib/xml2: xslt_process() now reports XSLT-related error
 details

* It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()).
  Since it only supports old-school "generic" error handlers, which are no longer
  used in PG's libxml code, we reintroduced a "generic" error handler
  xml_generic_error_handler() in xml.c.
* The alternative would have been to expose PgXmlErrorContext in xml.h,
  so we could implement a generic handler in xslt_proc.c.
  This is obviously not desirable, as it would depend on USE_LIBXML.
* No longer use the PG_XML_STRICTNESS_LEGACY for error handling,
  but query the error_occurred-flag via pg_xml_error_occurred().
  The existance of this getter is another hint, that we are not supposed
  to expose PgXmlErrorContext in xml.h.
* This change means that xslt_process() now reports not only details
  about XML parsing errors, but XSLT-schema deviations and missing
  stylesheet parameters as well.
* The XSLT error messages now also contain line numbers.
  For that to work, we had to set a dummy "SQL" URL when parsing XML strings.
  This is important, since xsltPrintErrorContext() includes
  line numbers only if an URL is set.
* The xsltSaveResultToString() error handling has been removed.
  It can practically only fail in OOM situations and there is no reason
  to handle them any different than with the other libxslt functions.
* Updated test suite and added test case for detecting missing
  stylesheet parameters.
  This was initially reported here but has obviously been fixed in the
  meantime:
  https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com
---
 contrib/xml2/expected/xml2.out | 17 +++++++++++++++
 contrib/xml2/sql/xml2.sql      |  8 +++++++
 contrib/xml2/xslt_proc.c       | 40 ++++++++++++++++++++++++----------
 src/backend/utils/adt/xml.c    | 37 +++++++++++++++++++++++++++++++
 src/include/utils/xml.h        |  2 ++
 5 files changed, 92 insertions(+), 12 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 3d97b14..157d584 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0"
   </xsl:template>
 </xsl:stylesheet>$$);
 ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 7 element output
+File write for 0wn3d.txt refused
+runtime error: file SQL line 7 element output
+xsltDocumentElem: write rights for 0wn3d.txt denied
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
+ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 3 element value-of
+Variable 'n1' has not been declared.
+Undefined variable
+runtime error: file SQL line 3 element value-of
+XPath evaluation returned no result.
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index ef99d16..9d42ac8 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0"
     </sax:output>
   </xsl:template>
 </xsl:stylesheet>$$);
+
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index b720d89..f17cf9f 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -61,6 +61,10 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlChar    *resstr = NULL;
 	int			reslen = 0;
 
+	/* the previous libxslt error context */
+	xmlGenericErrorFunc saved_errfunc;
+	void	           *saved_errcxt;
+
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_PP(2);
@@ -74,35 +78,46 @@ xslt_process(PG_FUNCTION_ARGS)
 	}
 
 	/* Setup parser */
-	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
+
+	/*
+	 * Save the previous libxslt error context.
+	 */
+	saved_errfunc = xsltGenericError;
+	saved_errcxt = xsltGenericErrorContext;
+	xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler);
 
 	PG_TRY();
 	{
 		xmlDocPtr	ssdoc;
 		bool		xslt_sec_prefs_error;
 
-		/* Parse document */
+		/*
+		 * Parse document.
+		 * It's important to set an "URL", so libxslt includes
+		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 */
 		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
 								XML_PARSE_NOENT);
 
-		if (doctree == NULL)
+		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
 		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
 							  XML_PARSE_NOENT);
 
-		if (ssdoc == NULL)
+		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing stylesheet as XML document");
 
 		/* After this call we need not free ssdoc separately */
 		stylesheet = xsltParseStylesheetDoc(ssdoc);
 
-		if (stylesheet == NULL)
+		if (stylesheet == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to parse stylesheet");
 
@@ -137,11 +152,14 @@ xslt_process(PG_FUNCTION_ARGS)
 		restree = xsltApplyStylesheetUser(stylesheet, doctree, params,
 										  NULL, NULL, xslt_ctxt);
 
-		if (restree == NULL)
+		if (restree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to apply stylesheet");
 
 		resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);
+		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
+						"failed to save result to string");
 	}
 	PG_CATCH();
 	{
@@ -157,6 +175,7 @@ xslt_process(PG_FUNCTION_ARGS)
 			xmlFreeDoc(doctree);
 		xsltCleanupGlobals();
 
+		xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 		pg_xml_done(xmlerrcxt, true);
 
 		PG_RE_THROW();
@@ -170,12 +189,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlFreeDoc(doctree);
 	xsltCleanupGlobals();
 
+	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	/* XXX this is pretty dubious, really ought to throw error instead */
-	if (resstat < 0)
-		PG_RETURN_NULL();
-
 	result = cstring_to_text_with_len((char *) resstr, reslen);
 
 	if (resstr)
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index db8d0d6..74f78c5 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2078,6 +2078,43 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 			 detail ? errdetail_internal("%s", detail) : 0));
 }
 
+/*
+ * Generic error handler for libxml errors and warnings.
+ * This is not used by this module, but may be useful for
+ * libxml-based libraries like libxslt, which do not support
+ * structured error handlers.
+ */
+void
+xml_generic_error_handler(void *data, const char * msg, ...)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	StringInfo errorBuf;
+	va_list ap;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxslt would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext");
+
+	/* Prepare error message in errorBuf */
+	errorBuf = makeStringInfo();
+	va_start(ap, msg);
+	appendStringInfoVA(errorBuf, msg, ap);
+	va_end(ap);
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(errorBuf);
+
+	appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+	appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data,
+						   errorBuf->len);
+
+	destroyStringInfo(errorBuf);
+}
 
 /*
  * Error handler for libxml errors and warnings
diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h
index 0d7a816..a754d8f 100644
--- a/src/include/utils/xml.h
+++ b/src/include/utils/xml.h
@@ -66,6 +66,8 @@ extern void pg_xml_init_library(void);
 extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness);
 extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError);
 extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt);
+extern void xml_generic_error_handler(void *data, const char * msg, ...)
+									 pg_attribute_printf(2, 3);
 extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode,
 						const char *msg);
 
-- 
2.48.1

From b4d9a6594142cf85e4e38352f6be3cea260962f7 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Thu, 17 Apr 2025 13:15:48 +0300
Subject: [PATCH v2] contrib/xml2: xslt_process() now reports XSLT-related
 error details

* It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()).
  Since it only supports old-school "generic" error handlers, which are no longer
  used in PG's libxml code, we reintroduced a "generic" error handler
  xml_generic_error_handler() in xml.c.
* The alternative would have been to expose PgXmlErrorContext in xml.h,
  so we could implement a generic handler in xslt_proc.c.
  This is obviously not desirable, as it would depend on USE_LIBXML.
* No longer use the PG_XML_STRICTNESS_LEGACY for error handling,
  but query the error_occurred-flag via pg_xml_error_occurred().
  The existance of this getter is another hint, that we are not supposed
  to expose PgXmlErrorContext in xml.h.
* This change means that xslt_process() now reports not only details
  about XML parsing errors, but XSLT-schema deviations and missing
  stylesheet parameters as well.
* The XSLT error messages now also contain line numbers.
  For that to work, we had to set a dummy "SQL" URL when parsing XML strings.
  This is important, since xsltPrintErrorContext() includes
  line numbers only if an URL is set.
* The xsltSaveResultToString() error handling has been removed.
  It can practically only fail in OOM situations and there is no reason
  to handle them any different than with the other libxslt functions.
* Updated test suite and added test case for detecting missing
  stylesheet parameters.
  This was initially reported here but has obviously been fixed in the
  meantime:
  https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com
---
 contrib/xml2/expected/xml2.out | 17 +++++++++++++++
 contrib/xml2/sql/xml2.sql      |  8 +++++++
 contrib/xml2/xslt_proc.c       | 39 +++++++++++++++++++++++-----------
 src/backend/utils/adt/xml.c    | 29 +++++++++++++++++++++++++
 src/include/utils/xml.h        |  2 ++
 5 files changed, 83 insertions(+), 12 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 3d97b14..157d584 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0"
   </xsl:template>
 </xsl:stylesheet>$$);
 ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 7 element output
+File write for 0wn3d.txt refused
+runtime error: file SQL line 7 element output
+xsltDocumentElem: write rights for 0wn3d.txt denied
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
+ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 3 element value-of
+Variable 'n1' has not been declared.
+Undefined variable
+runtime error: file SQL line 3 element value-of
+XPath evaluation returned no result.
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index ef99d16..9d42ac8 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0"
     </sax:output>
   </xsl:template>
 </xsl:stylesheet>$$);
+
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index b720d89..2aa44d3 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -61,6 +61,10 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlChar    *resstr = NULL;
 	int			reslen = 0;
 
+	/* the previous libxslt error context */
+	xmlGenericErrorFunc saved_errfunc;
+	void	   *saved_errcxt;
+
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_PP(2);
@@ -74,35 +78,45 @@ xslt_process(PG_FUNCTION_ARGS)
 	}
 
 	/* Setup parser */
-	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
+
+	/*
+	 * Save the previous libxslt error context.
+	 */
+	saved_errfunc = xsltGenericError;
+	saved_errcxt = xsltGenericErrorContext;
+	xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler);
 
 	PG_TRY();
 	{
 		xmlDocPtr	ssdoc;
 		bool		xslt_sec_prefs_error;
 
-		/* Parse document */
+		/*
+		 * Parse document. It's important to set an "URL", so libxslt includes
+		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 */
 		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
 								XML_PARSE_NOENT);
 
-		if (doctree == NULL)
+		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
 		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
 							  XML_PARSE_NOENT);
 
-		if (ssdoc == NULL)
+		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing stylesheet as XML document");
 
 		/* After this call we need not free ssdoc separately */
 		stylesheet = xsltParseStylesheetDoc(ssdoc);
 
-		if (stylesheet == NULL)
+		if (stylesheet == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to parse stylesheet");
 
@@ -137,11 +151,14 @@ xslt_process(PG_FUNCTION_ARGS)
 		restree = xsltApplyStylesheetUser(stylesheet, doctree, params,
 										  NULL, NULL, xslt_ctxt);
 
-		if (restree == NULL)
+		if (restree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to apply stylesheet");
 
 		resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);
+		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
+						"failed to save result to string");
 	}
 	PG_CATCH();
 	{
@@ -157,6 +174,7 @@ xslt_process(PG_FUNCTION_ARGS)
 			xmlFreeDoc(doctree);
 		xsltCleanupGlobals();
 
+		xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 		pg_xml_done(xmlerrcxt, true);
 
 		PG_RE_THROW();
@@ -170,12 +188,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlFreeDoc(doctree);
 	xsltCleanupGlobals();
 
+	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	/* XXX this is pretty dubious, really ought to throw error instead */
-	if (resstat < 0)
-		PG_RETURN_NULL();
-
 	result = cstring_to_text_with_len((char *) resstr, reslen);
 
 	if (resstr)
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index db8d0d6..61b0e2e 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2078,6 +2078,35 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 			 detail ? errdetail_internal("%s", detail) : 0));
 }
 
+/*
+ * Generic error handler for libxml errors and warnings.
+ * This is not used by this module, but may be useful for
+ * libxml-based libraries like libxslt, which do not support
+ * structured error handlers.
+ */
+void
+xml_generic_error_handler(void *data, const char *msg,...)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	va_list		ap;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxslt would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext");
+
+	appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+	va_start(ap, msg);
+	appendStringInfoVA(&xmlerrcxt->err_buf, msg, ap);
+	va_end(ap);
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(&xmlerrcxt->err_buf);
+}
 
 /*
  * Error handler for libxml errors and warnings
diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h
index 0d7a816..7cb101e 100644
--- a/src/include/utils/xml.h
+++ b/src/include/utils/xml.h
@@ -66,6 +66,8 @@ extern void pg_xml_init_library(void);
 extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness);
 extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError);
 extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt);
+extern void xml_generic_error_handler(void *data, const char *msg,...)
+			pg_attribute_printf(2, 3);
 extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode,
 						const char *msg);
 
-- 
2.48.1

From fa55bf28a2a45ae91a3363792b39e77d7c055cd2 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Thu, 17 Apr 2025 13:15:48 +0300
Subject: [PATCH v3 1/2] contrib/xml2: xslt_process() now reports XSLT-related
 error details

* It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()).
  Since it only supports old-school "generic" error handlers, which are no longer
  used in PG's libxml code, we reintroduced a "generic" error handler
  xml_generic_error_handler() in xml.c.
* The alternative would have been to expose PgXmlErrorContext in xml.h,
  so we could implement a generic handler in xslt_proc.c.
  This is obviously not desirable, as it would depend on USE_LIBXML.
* No longer use the PG_XML_STRICTNESS_LEGACY for error handling,
  but query the error_occurred-flag via pg_xml_error_occurred().
  The existance of this getter is another hint, that we are not supposed
  to expose PgXmlErrorContext in xml.h.
* This change means that xslt_process() now reports not only details
  about XML parsing errors, but XSLT-schema deviations and missing
  stylesheet parameters as well.
* The XSLT error messages now also contain line numbers.
  For that to work, we had to set a dummy "SQL" URL when parsing XML strings.
  This is important, since xsltPrintErrorContext() includes
  line numbers only if an URL is set.
* The xsltSaveResultToString() error handling has been removed.
  It can practically only fail in OOM situations and there is no reason
  to handle them any different than with the other libxslt functions.
* Updated test suite and added test case for detecting missing
  stylesheet parameters.
  This was initially reported here but has obviously been fixed in the
  meantime:
  https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com
---
 contrib/xml2/expected/xml2.out | 17 +++++++++++++++
 contrib/xml2/sql/xml2.sql      |  8 +++++++
 contrib/xml2/xslt_proc.c       | 39 +++++++++++++++++++++++-----------
 src/backend/utils/adt/xml.c    | 29 +++++++++++++++++++++++++
 src/include/utils/xml.h        |  2 ++
 5 files changed, 83 insertions(+), 12 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 3d97b14c3a..157d584e63 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0"
   </xsl:template>
 </xsl:stylesheet>$$);
 ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 7 element output
+File write for 0wn3d.txt refused
+runtime error: file SQL line 7 element output
+xsltDocumentElem: write rights for 0wn3d.txt denied
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
+ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 3 element value-of
+Variable 'n1' has not been declared.
+Undefined variable
+runtime error: file SQL line 3 element value-of
+XPath evaluation returned no result.
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index ef99d164f2..9d42ac8a0b 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0"
     </sax:output>
   </xsl:template>
 </xsl:stylesheet>$$);
+
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index b720d89f75..2aa44d39e7 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -61,6 +61,10 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlChar    *resstr = NULL;
 	int			reslen = 0;
 
+	/* the previous libxslt error context */
+	xmlGenericErrorFunc saved_errfunc;
+	void	   *saved_errcxt;
+
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_PP(2);
@@ -74,35 +78,45 @@ xslt_process(PG_FUNCTION_ARGS)
 	}
 
 	/* Setup parser */
-	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
+
+	/*
+	 * Save the previous libxslt error context.
+	 */
+	saved_errfunc = xsltGenericError;
+	saved_errcxt = xsltGenericErrorContext;
+	xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler);
 
 	PG_TRY();
 	{
 		xmlDocPtr	ssdoc;
 		bool		xslt_sec_prefs_error;
 
-		/* Parse document */
+		/*
+		 * Parse document. It's important to set an "URL", so libxslt includes
+		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 */
 		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
 								XML_PARSE_NOENT);
 
-		if (doctree == NULL)
+		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
 		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
 							  XML_PARSE_NOENT);
 
-		if (ssdoc == NULL)
+		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing stylesheet as XML document");
 
 		/* After this call we need not free ssdoc separately */
 		stylesheet = xsltParseStylesheetDoc(ssdoc);
 
-		if (stylesheet == NULL)
+		if (stylesheet == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to parse stylesheet");
 
@@ -137,11 +151,14 @@ xslt_process(PG_FUNCTION_ARGS)
 		restree = xsltApplyStylesheetUser(stylesheet, doctree, params,
 										  NULL, NULL, xslt_ctxt);
 
-		if (restree == NULL)
+		if (restree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to apply stylesheet");
 
 		resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);
+		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
+						"failed to save result to string");
 	}
 	PG_CATCH();
 	{
@@ -157,6 +174,7 @@ xslt_process(PG_FUNCTION_ARGS)
 			xmlFreeDoc(doctree);
 		xsltCleanupGlobals();
 
+		xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 		pg_xml_done(xmlerrcxt, true);
 
 		PG_RE_THROW();
@@ -170,12 +188,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlFreeDoc(doctree);
 	xsltCleanupGlobals();
 
+	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	/* XXX this is pretty dubious, really ought to throw error instead */
-	if (resstat < 0)
-		PG_RETURN_NULL();
-
 	result = cstring_to_text_with_len((char *) resstr, reslen);
 
 	if (resstr)
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index db8d0d6a7e..61b0e2e117 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2078,6 +2078,35 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 			 detail ? errdetail_internal("%s", detail) : 0));
 }
 
+/*
+ * Generic error handler for libxml errors and warnings.
+ * This is not used by this module, but may be useful for
+ * libxml-based libraries like libxslt, which do not support
+ * structured error handlers.
+ */
+void
+xml_generic_error_handler(void *data, const char *msg,...)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	va_list		ap;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxslt would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext");
+
+	appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+	va_start(ap, msg);
+	appendStringInfoVA(&xmlerrcxt->err_buf, msg, ap);
+	va_end(ap);
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(&xmlerrcxt->err_buf);
+}
 
 /*
  * Error handler for libxml errors and warnings
diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h
index 0d7a816b9f..7cb101e81d 100644
--- a/src/include/utils/xml.h
+++ b/src/include/utils/xml.h
@@ -66,6 +66,8 @@ extern void pg_xml_init_library(void);
 extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness);
 extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError);
 extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt);
+extern void xml_generic_error_handler(void *data, const char *msg,...)
+			pg_attribute_printf(2, 3);
 extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode,
 						const char *msg);
 
-- 
2.49.0

From 7d77b0afd7f4b99baa93fbc9dd6ddd21a1a4c560 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Wed, 30 Apr 2025 13:19:42 +0300
Subject: [PATCH v3 2/2] contrib/xml2: overloaded xslt_process() to provide
 variants for xmltype and specifying parameters in arrays

* There are apparently no functions that accept XML as text, except for xmlparse().
  xslt_process() should therefore also accept xmltype.
* A version accepting text is still kept for backwards compatibility, but is considered
  deprecated.
* The new xmltype-based version expects an array of stylesheet parameter-value pairs,
  which is less limited than the now deprecated way of encoding all stylesheet parameters into
  a single text argument.
  We can now accept an arbitrary number of parameters and you can include `=` and `,` signs
  in both the key and value strings.
  Hstores haven't been used since they are in a module and we don't want to depend on any
  additional module.
* The new implementation respects the database's encoding - text strings are always converted to UTF8
  before passing them into libxml2.
* On the downside, xml_parse() had to be made an external function.
  Since a declaration cannot be added to xml.h without drawing in libxml2 headers,
  the declaration is repeated in xslt_proc.c.
  Perhaps xml_parse() should be declared in a separate internal header?
* xmlCtxtReadDoc() now sets a dummy "SQL" URL to preserve line numbers in XSLT stylesheet errors.
  This change at least does not break the test suite.
---
 contrib/xml2/expected/xml2.out |  13 +++
 contrib/xml2/sql/xml2.sql      |   8 ++
 contrib/xml2/xml2--1.1.sql     |  11 +++
 contrib/xml2/xslt_proc.c       | 147 ++++++++++++++++++++++++++-------
 doc/src/sgml/xml2.sgml         |  19 +++--
 src/backend/utils/adt/xml.c    |  19 +++--
 6 files changed, 174 insertions(+), 43 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 157d584e63..0a8a628020 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -278,3 +278,16 @@ Variable 'n1' has not been declared.
 Undefined variable
 runtime error: file SQL line 3 element value-of
 XPath evaluation returned no result.
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
+ xslt_process 
+--------------
+ foo         +
+ 
+(1 row)
+
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index 9d42ac8a0b..7555854d49 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -161,3 +161,11 @@ $$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
     <value-of select="$n1"/>
   </template>
 </stylesheet>$$)::xml;
+
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
diff --git a/contrib/xml2/xml2--1.1.sql b/contrib/xml2/xml2--1.1.sql
index 671372cb27..a579a1e5e1 100644
--- a/contrib/xml2/xml2--1.1.sql
+++ b/contrib/xml2/xml2--1.1.sql
@@ -71,3 +71,14 @@ CREATE FUNCTION xslt_process(text,text)
 RETURNS text
 AS 'MODULE_PATHNAME'
 LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
+
+CREATE FUNCTION xslt_process(xml,xml,text[])
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
+
+-- the function checks for the correct argument count
+CREATE FUNCTION xslt_process(xml,xml)
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index 2aa44d39e7..2a29b13f88 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -10,6 +10,9 @@
 #include "fmgr.h"
 #include "utils/builtins.h"
 #include "utils/xml.h"
+#include "utils/array.h"
+#include "utils/memutils.h"
+#include "mb/pg_wchar.h"
 
 #ifdef USE_LIBXSLT
 
@@ -35,9 +38,18 @@
 extern PgXmlErrorContext *pgxml_parser_init(PgXmlStrictness strictness);
 
 /* local defs */
+static xmltype *xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params);
 static const char **parse_params(text *paramstr);
 #endif							/* USE_LIBXSLT */
 
+/*
+ * FIXME: This cannot easily be exposed in xml.h.
+ * Perhaps there should be an xml-internal.h?
+ */
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 
 PG_FUNCTION_INFO_V1(xslt_process);
 
@@ -48,9 +60,103 @@ xslt_process(PG_FUNCTION_ARGS)
 
 	text	   *doct = PG_GETARG_TEXT_PP(0);
 	text	   *ssheet = PG_GETARG_TEXT_PP(1);
+	const char **params = NULL;
+	text	   *result;
+
+	if (fcinfo->nargs == 3)
+	{
+		text	   *paramstr = PG_GETARG_TEXT_PP(2);
+
+		params = parse_params(paramstr);
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_TEXT_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+PG_FUNCTION_INFO_V1(xslt_process_xmltype);
+
+Datum
+xslt_process_xmltype(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXSLT
+
+	xmltype    *doct = PG_GETARG_XML_P(0);
+	xmltype    *ssheet = PG_GETARG_XML_P(1);
+	const char **params = NULL;
+	xmltype    *result;
+
+	/*
+	 * Parameters are key-value pairs. The values are XPath expressions, so
+	 * strings will have to be escaped with single or double quotes. Even
+	 * `xsltproc --stringparam` does nothing else than adding single or double
+	 * quotes and fails if the value contains both.
+	 */
+	if (fcinfo->nargs == 3)
+	{
+		ArrayType  *paramarray = PG_GETARG_ARRAYTYPE_P(2);
+		Datum	   *arr_datums;
+		bool	   *arr_nulls;
+		int			arr_count;
+		int			i,
+					j;
+
+		deconstruct_array_builtin(paramarray, TEXTOID, &arr_datums, &arr_nulls, &arr_count);
+
+		if ((arr_count % 2) != 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_ARRAY_ELEMENT_ERROR),
+					 errmsg("number of stylesheet parameters (%d) must be a multiple of 2",
+							arr_count)));
+
+		params = palloc_array(const char *, arr_count + 1);
+
+		for (i = 0, j = 0; i < arr_count; i++)
+		{
+			char	   *cstr;
+
+			if (arr_nulls[i])
+				continue;
+
+			cstr = TextDatumGetCString(arr_datums[i]);
+			params[j++] = (char *) pg_do_encoding_conversion((unsigned char *) cstr,
+															 strlen(cstr),
+															 GetDatabaseEncoding(),
+															 PG_UTF8);
+		}
+		params[j] = NULL;
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_XML_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+#ifdef USE_LIBXSLT
+
+static xmltype *
+xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params)
+{
 	text	   *result;
-	text	   *paramstr;
-	const char **params;
 	PgXmlErrorContext *xmlerrcxt;
 	volatile xsltStylesheetPtr stylesheet = NULL;
 	volatile xmlDocPtr doctree = NULL;
@@ -65,18 +171,6 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlGenericErrorFunc saved_errfunc;
 	void	   *saved_errcxt;
 
-	if (fcinfo->nargs == 3)
-	{
-		paramstr = PG_GETARG_TEXT_PP(2);
-		params = parse_params(paramstr);
-	}
-	else
-	{
-		/* No parameters */
-		params = (const char **) palloc(sizeof(char *));
-		params[0] = NULL;
-	}
-
 	/* Setup parser */
 	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
 
@@ -96,18 +190,16 @@ xslt_process(PG_FUNCTION_ARGS)
 		 * Parse document. It's important to set an "URL", so libxslt includes
 		 * line numbers in error messages (cf. xsltPrintErrorContext()).
 		 */
-		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
-								XML_PARSE_NOENT);
+		doctree = xml_parse(doct, XMLOPTION_DOCUMENT, true,
+							GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
-		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
-							  XML_PARSE_NOENT);
+		ssdoc = xml_parse(ssheet, XMLOPTION_DOCUMENT, true,
+						  GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
@@ -155,6 +247,10 @@ xslt_process(PG_FUNCTION_ARGS)
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
 						"failed to apply stylesheet");
 
+		/*
+		 * FIXME: There is probably a function to convert the string to the
+		 * correct database encoding.
+		 */
 		resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);
 		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
@@ -196,18 +292,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	if (resstr)
 		xmlFree(resstr);
 
-	PG_RETURN_TEXT_P(result);
-#else							/* !USE_LIBXSLT */
-
-	ereport(ERROR,
-			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			 errmsg("xslt_process() is not available without libxslt")));
-	PG_RETURN_NULL();
-#endif							/* USE_LIBXSLT */
+	return result;
 }
 
-#ifdef USE_LIBXSLT
-
 static const char **
 parse_params(text *paramstr)
 {
diff --git a/doc/src/sgml/xml2.sgml b/doc/src/sgml/xml2.sgml
index 9fd613f967..dc6fb40121 100644
--- a/doc/src/sgml/xml2.sgml
+++ b/doc/src/sgml/xml2.sgml
@@ -408,22 +408,29 @@ ORDER BY doc_num, line_num;
   </indexterm>
 
 <synopsis>
-xslt_process(text document, text stylesheet, text paramlist) returns text
+xslt_process(xml document, xml stylesheet, text[] paramlist) returns xml
 </synopsis>
 
    <para>
     This function applies the XSL stylesheet to the document and returns
-    the transformed result. The <literal>paramlist</literal> is a list of parameter
-    assignments to be used in the transformation, specified in the form
-    <literal>a=1,b=2</literal>. Note that the
-    parameter parsing is very simple-minded: parameter values cannot
-    contain commas!
+    the transformed result. The <literal>paramlist</literal> is an array of parameter
+    assignments to be used in the transformation, specified in pairs of
+    key and value strings (e.g. <literal>ARRAY['a','1', 'b','2']</literal>).
+    The length of the array must be even.
+    Note that the values are still interpreted as XPath expressions, so string values need to
+    be quoted in single or double quotes (e.g. <literal>ARRAY['a','"string"']</literal>).
    </para>
 
    <para>
     There is also a two-parameter version of <function>xslt_process</function> which
     does not pass any parameters to the transformation.
    </para>
+
+   <para>
+    <emphasis>Deprecated</emphasis> variants of <function>xslt_process</function> accepting
+    text arguments and parameters encoded into single text strings
+    (e.g. <literal>a=1,b=2</literal>) are also still available.
+   </para>
   </sect3>
  </sect2>
 
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 61b0e2e117..08faa0dc86 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -155,11 +155,11 @@ static int	parse_xml_decl(const xmlChar *str, size_t *lenp,
 static bool print_xml_decl(StringInfo buf, const xmlChar *version,
 						   pg_enc encoding, int standalone);
 static bool xml_doctype_in_content(const xmlChar *str);
-static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
-						   bool preserve_whitespace, int encoding,
-						   XmlOptionType *parsed_xmloptiontype,
-						   xmlNodePtr *parsed_nodes,
-						   Node *escontext);
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype,
+					  xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 static text *xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt);
 static int	xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 								   ArrayBuildState *astate,
@@ -1732,7 +1732,7 @@ xml_doctype_in_content(const xmlChar *str)
  * TODO maybe libxml2's xmlreader is better? (do not construct DOM,
  * yet do not use SAX - see xmlreader.c)
  */
-static xmlDocPtr
+xmlDocPtr
 xml_parse(text *data, XmlOptionType xmloption_arg,
 		  bool preserve_whitespace, int encoding,
 		  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
@@ -1828,8 +1828,13 @@ xml_parse(text *data, XmlOptionType xmloption_arg,
 				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
 							"could not allocate parser context");
 
+			/*
+			 * Setting a dummy "SQL" URL is important for the
+			 * xsltPrintErrorContext() when using the legacy text-based
+			 * xslt_process() variant.
+			 */
 			doc = xmlCtxtReadDoc(ctxt, utf8string,
-								 NULL,	/* no URL */
+								 "SQL",
 								 "UTF-8",
 								 options);
 
-- 
2.49.0

From 237ae8788150249699e17fda2e47363d917b5ffe Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Thu, 17 Apr 2025 13:15:48 +0300
Subject: [PATCH v4 1/2] contrib/xml2: xslt_process() now reports XSLT-related
 error details

* It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()).
  Since it only supports old-school "generic" error handlers, which are no longer
  used in PG's libxml code, we reintroduced a "generic" error handler
  xml_generic_error_handler() in xml.c.
* The alternative would have been to expose PgXmlErrorContext in xml.h,
  so we could implement a generic handler in xslt_proc.c.
  This is obviously not desirable, as it would depend on USE_LIBXML.
* No longer use the PG_XML_STRICTNESS_LEGACY for error handling as
  the err_occurred flag was already checked via pg_xml_error_occurred()
  since 732061150b004385810e522f8629f5bf91d977b7.
* This change means that xslt_process() now reports not only details
  about XML parsing errors, but XSLT-schema deviations and missing
  stylesheet parameters as well.
* The XSLT error messages now also contain line numbers.
  For that to work, we had to set a dummy "SQL" URL when parsing XML strings.
  This is important, since xsltPrintErrorContext() includes
  line numbers only if an URL is set.
* The special xsltSaveResultToString() error handling has been removed.
  It can practically only fail in OOM situations and there is no reason
  to handle them any different than with the other libxslt functions.
* Updated test suite and added test case for detecting missing
  stylesheet parameters.
  This was initially reported here but has obviously been fixed in the
  meantime:
  https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com
---
 contrib/xml2/expected/xml2.out | 17 +++++++++++++++++
 contrib/xml2/sql/xml2.sql      |  8 ++++++++
 contrib/xml2/xslt_proc.c       | 35 +++++++++++++++++++++++-----------
 src/backend/utils/adt/xml.c    | 29 ++++++++++++++++++++++++++++
 src/include/utils/xml.h        |  2 ++
 5 files changed, 80 insertions(+), 11 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 3d97b14c3a..157d584e63 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0"
   </xsl:template>
 </xsl:stylesheet>$$);
 ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 7 element output
+File write for 0wn3d.txt refused
+runtime error: file SQL line 7 element output
+xsltDocumentElem: write rights for 0wn3d.txt denied
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
+ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 3 element value-of
+Variable 'n1' has not been declared.
+Undefined variable
+runtime error: file SQL line 3 element value-of
+XPath evaluation returned no result.
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index ef99d164f2..9d42ac8a0b 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0"
     </sax:output>
   </xsl:template>
 </xsl:stylesheet>$$);
+
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index c8e7dd45ed..5efb659439 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -61,6 +61,10 @@ xslt_process(PG_FUNCTION_ARGS)
 	volatile xmlChar *resstr = NULL;
 	int			reslen = 0;
 
+	/* the previous libxslt error context */
+	xmlGenericErrorFunc saved_errfunc;
+	void	   *saved_errcxt;
+
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_PP(2);
@@ -74,16 +78,26 @@ xslt_process(PG_FUNCTION_ARGS)
 	}
 
 	/* Setup parser */
-	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
+
+	/*
+	 * Save the previous libxslt error context.
+	 */
+	saved_errfunc = xsltGenericError;
+	saved_errcxt = xsltGenericErrorContext;
+	xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler);
 
 	PG_TRY();
 	{
 		xmlDocPtr	ssdoc;
 		bool		xslt_sec_prefs_error;
 
-		/* Parse document */
+		/*
+		 * Parse document. It's important to set an "URL", so libxslt includes
+		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 */
 		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
 								XML_PARSE_NOENT);
 
 		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
@@ -92,7 +106,7 @@ xslt_process(PG_FUNCTION_ARGS)
 
 		/* Same for stylesheet */
 		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
 							  XML_PARSE_NOENT);
 
 		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
@@ -143,9 +157,10 @@ xslt_process(PG_FUNCTION_ARGS)
 
 		resstat = xsltSaveResultToString((xmlChar **) &resstr, &reslen,
 										 restree, stylesheet);
-
-		if (resstat >= 0)
-			result = cstring_to_text_with_len((char *) resstr, reslen);
+		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
+						"failed to save result to string");
+		result = cstring_to_text_with_len((char *) resstr, reslen);
 	}
 	PG_CATCH();
 	{
@@ -163,6 +178,7 @@ xslt_process(PG_FUNCTION_ARGS)
 			xmlFree((xmlChar *) resstr);
 		xsltCleanupGlobals();
 
+		xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 		pg_xml_done(xmlerrcxt, true);
 
 		PG_RE_THROW();
@@ -179,12 +195,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	if (resstr)
 		xmlFree((xmlChar *) resstr);
 
+	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	/* XXX this is pretty dubious, really ought to throw error instead */
-	if (resstat < 0)
-		PG_RETURN_NULL();
-
 	PG_RETURN_TEXT_P(result);
 #else							/* !USE_LIBXSLT */
 
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 2bd39b6ac4..080d9d2ad9 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2130,6 +2130,35 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 			 detail ? errdetail_internal("%s", detail) : 0));
 }
 
+/*
+ * Generic error handler for libxml errors and warnings.
+ * This is not used by this module, but may be useful for
+ * libxml-based libraries like libxslt, which do not support
+ * structured error handlers.
+ */
+void
+xml_generic_error_handler(void *data, const char *msg,...)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	va_list		ap;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxslt would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext");
+
+	appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+	va_start(ap, msg);
+	appendStringInfoVA(&xmlerrcxt->err_buf, msg, ap);
+	va_end(ap);
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(&xmlerrcxt->err_buf);
+}
 
 /*
  * Error handler for libxml errors and warnings
diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h
index 0d7a816b9f..7cb101e81d 100644
--- a/src/include/utils/xml.h
+++ b/src/include/utils/xml.h
@@ -66,6 +66,8 @@ extern void pg_xml_init_library(void);
 extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness);
 extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError);
 extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt);
+extern void xml_generic_error_handler(void *data, const char *msg,...)
+			pg_attribute_printf(2, 3);
 extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode,
 						const char *msg);
 
-- 
2.49.0

From f4996f6278fc575ad67e16bf21d00f0be7907457 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Wed, 30 Apr 2025 13:19:42 +0300
Subject: [PATCH v4 2/2] contrib/xml2: overloaded xslt_process() to provide
 variants for xmltype and specifying parameters in arrays

* There are apparently no functions that accept XML as text, except for xmlparse().
  xslt_process() should therefore also accept xmltype.
* A version accepting text is still kept for backwards compatibility, but is considered
  deprecated.
* The new xmltype-based version expects an array of stylesheet parameter-value pairs,
  which is less limited than the now deprecated way of encoding all stylesheet parameters into
  a single text argument.
  We can now accept an arbitrary number of parameters and you can include `=` and `,` signs
  in both the key and value strings.
  Hstores haven't been used since they are in a module and we don't want to depend on any
  additional module.
* The new implementation respects the database's encoding - text strings are always converted to UTF8
  before passing them into libxml2.
* On the downside, xml_parse() had to be made an external function.
  Since a declaration cannot be added to xml.h without drawing in libxml2 headers,
  the declaration is repeated in xslt_proc.c.
  Perhaps xml_parse() should be declared in a separate internal header?
* xmlCtxtReadDoc() now sets a dummy "SQL" URL to preserve line numbers in XSLT stylesheet errors.
  This change at least does not break the test suite.
---
 contrib/xml2/expected/xml2.out |  13 +++
 contrib/xml2/sql/xml2.sql      |   8 ++
 contrib/xml2/xml2--1.1.sql     |  11 +++
 contrib/xml2/xslt_proc.c       | 146 +++++++++++++++++++++++++--------
 doc/src/sgml/xml2.sgml         |  19 +++--
 src/backend/utils/adt/xml.c    |  19 +++--
 6 files changed, 171 insertions(+), 45 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 157d584e63..0a8a628020 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -278,3 +278,16 @@ Variable 'n1' has not been declared.
 Undefined variable
 runtime error: file SQL line 3 element value-of
 XPath evaluation returned no result.
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
+ xslt_process 
+--------------
+ foo         +
+ 
+(1 row)
+
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index 9d42ac8a0b..7555854d49 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -161,3 +161,11 @@ $$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
     <value-of select="$n1"/>
   </template>
 </stylesheet>$$)::xml;
+
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
diff --git a/contrib/xml2/xml2--1.1.sql b/contrib/xml2/xml2--1.1.sql
index 671372cb27..a579a1e5e1 100644
--- a/contrib/xml2/xml2--1.1.sql
+++ b/contrib/xml2/xml2--1.1.sql
@@ -71,3 +71,14 @@ CREATE FUNCTION xslt_process(text,text)
 RETURNS text
 AS 'MODULE_PATHNAME'
 LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
+
+CREATE FUNCTION xslt_process(xml,xml,text[])
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
+
+-- the function checks for the correct argument count
+CREATE FUNCTION xslt_process(xml,xml)
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index 5efb659439..c31ed9d039 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -10,6 +10,9 @@
 #include "fmgr.h"
 #include "utils/builtins.h"
 #include "utils/xml.h"
+#include "utils/array.h"
+#include "utils/memutils.h"
+#include "mb/pg_wchar.h"
 
 #ifdef USE_LIBXSLT
 
@@ -35,9 +38,18 @@
 extern PgXmlErrorContext *pgxml_parser_init(PgXmlStrictness strictness);
 
 /* local defs */
+static xmltype *xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params);
 static const char **parse_params(text *paramstr);
 #endif							/* USE_LIBXSLT */
 
+/*
+ * FIXME: This cannot easily be exposed in xml.h.
+ * Perhaps there should be an xml-internal.h?
+ */
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 
 PG_FUNCTION_INFO_V1(xslt_process);
 
@@ -48,9 +60,103 @@ xslt_process(PG_FUNCTION_ARGS)
 
 	text	   *doct = PG_GETARG_TEXT_PP(0);
 	text	   *ssheet = PG_GETARG_TEXT_PP(1);
+	const char **params = NULL;
+	text	   *result;
+
+	if (fcinfo->nargs == 3)
+	{
+		text	   *paramstr = PG_GETARG_TEXT_PP(2);
+
+		params = parse_params(paramstr);
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_TEXT_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+PG_FUNCTION_INFO_V1(xslt_process_xmltype);
+
+Datum
+xslt_process_xmltype(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXSLT
+
+	xmltype    *doct = PG_GETARG_XML_P(0);
+	xmltype    *ssheet = PG_GETARG_XML_P(1);
+	const char **params = NULL;
+	xmltype    *result;
+
+	/*
+	 * Parameters are key-value pairs. The values are XPath expressions, so
+	 * strings will have to be escaped with single or double quotes. Even
+	 * `xsltproc --stringparam` does nothing else than adding single or double
+	 * quotes and fails if the value contains both.
+	 */
+	if (fcinfo->nargs == 3)
+	{
+		ArrayType  *paramarray = PG_GETARG_ARRAYTYPE_P(2);
+		Datum	   *arr_datums;
+		bool	   *arr_nulls;
+		int			arr_count;
+		int			i,
+					j;
+
+		deconstruct_array_builtin(paramarray, TEXTOID, &arr_datums, &arr_nulls, &arr_count);
+
+		if ((arr_count % 2) != 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_ARRAY_ELEMENT_ERROR),
+					 errmsg("number of stylesheet parameters (%d) must be a multiple of 2",
+							arr_count)));
+
+		params = palloc_array(const char *, arr_count + 1);
+
+		for (i = 0, j = 0; i < arr_count; i++)
+		{
+			char	   *cstr;
+
+			if (arr_nulls[i])
+				continue;
+
+			cstr = TextDatumGetCString(arr_datums[i]);
+			params[j++] = (char *) pg_do_encoding_conversion((unsigned char *) cstr,
+															 strlen(cstr),
+															 GetDatabaseEncoding(),
+															 PG_UTF8);
+		}
+		params[j] = NULL;
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_XML_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+#ifdef USE_LIBXSLT
+
+static xmltype *
+xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params)
+{
 	text	   *result;
-	text	   *paramstr;
-	const char **params;
 	PgXmlErrorContext *xmlerrcxt;
 	volatile xsltStylesheetPtr stylesheet = NULL;
 	volatile xmlDocPtr doctree = NULL;
@@ -65,18 +171,6 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlGenericErrorFunc saved_errfunc;
 	void	   *saved_errcxt;
 
-	if (fcinfo->nargs == 3)
-	{
-		paramstr = PG_GETARG_TEXT_PP(2);
-		params = parse_params(paramstr);
-	}
-	else
-	{
-		/* No parameters */
-		params = (const char **) palloc(sizeof(char *));
-		params[0] = NULL;
-	}
-
 	/* Setup parser */
 	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
 
@@ -93,21 +187,18 @@ xslt_process(PG_FUNCTION_ARGS)
 		bool		xslt_sec_prefs_error;
 
 		/*
-		 * Parse document. It's important to set an "URL", so libxslt includes
-		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 * Parse document.
 		 */
-		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
-								XML_PARSE_NOENT);
+		doctree = xml_parse(doct, XMLOPTION_DOCUMENT, true,
+							GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
-		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
-							  XML_PARSE_NOENT);
+		ssdoc = xml_parse(ssheet, XMLOPTION_DOCUMENT, true,
+						  GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
@@ -198,18 +289,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	PG_RETURN_TEXT_P(result);
-#else							/* !USE_LIBXSLT */
-
-	ereport(ERROR,
-			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			 errmsg("xslt_process() is not available without libxslt")));
-	PG_RETURN_NULL();
-#endif							/* USE_LIBXSLT */
+	return result;
 }
 
-#ifdef USE_LIBXSLT
-
 static const char **
 parse_params(text *paramstr)
 {
diff --git a/doc/src/sgml/xml2.sgml b/doc/src/sgml/xml2.sgml
index 9fd613f967..dc6fb40121 100644
--- a/doc/src/sgml/xml2.sgml
+++ b/doc/src/sgml/xml2.sgml
@@ -408,22 +408,29 @@ ORDER BY doc_num, line_num;
   </indexterm>
 
 <synopsis>
-xslt_process(text document, text stylesheet, text paramlist) returns text
+xslt_process(xml document, xml stylesheet, text[] paramlist) returns xml
 </synopsis>
 
    <para>
     This function applies the XSL stylesheet to the document and returns
-    the transformed result. The <literal>paramlist</literal> is a list of parameter
-    assignments to be used in the transformation, specified in the form
-    <literal>a=1,b=2</literal>. Note that the
-    parameter parsing is very simple-minded: parameter values cannot
-    contain commas!
+    the transformed result. The <literal>paramlist</literal> is an array of parameter
+    assignments to be used in the transformation, specified in pairs of
+    key and value strings (e.g. <literal>ARRAY['a','1', 'b','2']</literal>).
+    The length of the array must be even.
+    Note that the values are still interpreted as XPath expressions, so string values need to
+    be quoted in single or double quotes (e.g. <literal>ARRAY['a','"string"']</literal>).
    </para>
 
    <para>
     There is also a two-parameter version of <function>xslt_process</function> which
     does not pass any parameters to the transformation.
    </para>
+
+   <para>
+    <emphasis>Deprecated</emphasis> variants of <function>xslt_process</function> accepting
+    text arguments and parameters encoded into single text strings
+    (e.g. <literal>a=1,b=2</literal>) are also still available.
+   </para>
   </sect3>
  </sect2>
 
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 080d9d2ad9..c14352cb11 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -155,11 +155,11 @@ static int	parse_xml_decl(const xmlChar *str, size_t *lenp,
 static bool print_xml_decl(StringInfo buf, const xmlChar *version,
 						   pg_enc encoding, int standalone);
 static bool xml_doctype_in_content(const xmlChar *str);
-static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
-						   bool preserve_whitespace, int encoding,
-						   XmlOptionType *parsed_xmloptiontype,
-						   xmlNodePtr *parsed_nodes,
-						   Node *escontext);
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype,
+					  xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 static text *xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt);
 static int	xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 								   ArrayBuildState *astate,
@@ -1778,7 +1778,7 @@ xml_doctype_in_content(const xmlChar *str)
  * TODO maybe libxml2's xmlreader is better? (do not construct DOM,
  * yet do not use SAX - see xmlreader.c)
  */
-static xmlDocPtr
+xmlDocPtr
 xml_parse(text *data, XmlOptionType xmloption_arg,
 		  bool preserve_whitespace, int encoding,
 		  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
@@ -1874,8 +1874,13 @@ xml_parse(text *data, XmlOptionType xmloption_arg,
 				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
 							"could not allocate parser context");
 
+			/*
+			 * Setting a dummy "SQL" URL is important for the
+			 * xsltPrintErrorContext() when using the legacy text-based
+			 * xslt_process() variant.
+			 */
 			doc = xmlCtxtReadDoc(ctxt, utf8string,
-								 NULL,	/* no URL */
+								 "SQL",
 								 "UTF-8",
 								 options);
 
-- 
2.49.0

From 335a4d2cd7ee5b199db99e8861774acbf046b6c1 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Thu, 17 Apr 2025 13:15:48 +0300
Subject: [PATCH v5 1/2] contrib/xml2: xslt_process() now reports XSLT-related
 error details

* It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()).
  Since it only supports old-school "generic" error handlers, which are no longer
  used in PG's libxml code, we reintroduced a "generic" error handler
  xml_generic_error_handler() in xml.c.
* The alternative would have been to expose PgXmlErrorContext in xml.h,
  so we could implement a generic handler in xslt_proc.c.
  This is obviously not desirable, as it would depend on USE_LIBXML.
* No longer use the PG_XML_STRICTNESS_LEGACY for error handling as
  the err_occurred flag was already checked via pg_xml_error_occurred()
  since 732061150b004385810e522f8629f5bf91d977b7.
* This change means that xslt_process() now reports not only details
  about XML parsing errors, but XSLT-schema deviations and missing
  stylesheet parameters as well.
* The XSLT error messages now also contain line numbers.
  For that to work, we had to set a dummy "SQL" URL when parsing XML strings.
  This is important, since xsltPrintErrorContext() includes
  line numbers only if an URL is set.
* The special xsltSaveResultToString() error handling has been removed.
  It can practically only fail in OOM situations and there is no reason
  to handle them any different than with the other libxslt functions.
* Updated test suite and added test case for detecting missing
  stylesheet parameters.
  This was initially reported here but has obviously been fixed in the
  meantime:
  https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com
---
 contrib/xml2/expected/xml2.out | 17 +++++++++++++++++
 contrib/xml2/sql/xml2.sql      |  8 ++++++++
 contrib/xml2/xslt_proc.c       | 35 +++++++++++++++++++++++-----------
 src/backend/utils/adt/xml.c    | 29 ++++++++++++++++++++++++++++
 src/include/utils/xml.h        |  2 ++
 5 files changed, 80 insertions(+), 11 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 3d97b14c3a..157d584e63 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0"
   </xsl:template>
 </xsl:stylesheet>$$);
 ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 7 element output
+File write for 0wn3d.txt refused
+runtime error: file SQL line 7 element output
+xsltDocumentElem: write rights for 0wn3d.txt denied
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
+ERROR:  failed to apply stylesheet
+DETAIL:  runtime error: file SQL line 3 element value-of
+Variable 'n1' has not been declared.
+Undefined variable
+runtime error: file SQL line 3 element value-of
+XPath evaluation returned no result.
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index ef99d164f2..9d42ac8a0b 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0"
     </sax:output>
   </xsl:template>
 </xsl:stylesheet>$$);
+
+-- detecting missing stylesheet parameter
+SELECT xslt_process('<xml/>',
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$)::xml;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index 53550c7dc2..17776f78b5 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -60,6 +60,10 @@ xslt_process(PG_FUNCTION_ARGS)
 	volatile int resstat = -1;
 	xmlChar    *volatile resstr = NULL;
 
+	/* the previous libxslt error context */
+	xmlGenericErrorFunc saved_errfunc;
+	void	   *saved_errcxt;
+
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_PP(2);
@@ -73,7 +77,14 @@ xslt_process(PG_FUNCTION_ARGS)
 	}
 
 	/* Setup parser */
-	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
+
+	/*
+	 * Save the previous libxslt error context.
+	 */
+	saved_errfunc = xsltGenericError;
+	saved_errcxt = xsltGenericErrorContext;
+	xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler);
 
 	PG_TRY();
 	{
@@ -81,9 +92,12 @@ xslt_process(PG_FUNCTION_ARGS)
 		bool		xslt_sec_prefs_error;
 		int			reslen = 0;
 
-		/* Parse document */
+		/*
+		 * Parse document. It's important to set an "URL", so libxslt includes
+		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 */
 		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
 								XML_PARSE_NOENT);
 
 		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
@@ -92,7 +106,7 @@ xslt_process(PG_FUNCTION_ARGS)
 
 		/* Same for stylesheet */
 		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
 							  XML_PARSE_NOENT);
 
 		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
@@ -143,9 +157,10 @@ xslt_process(PG_FUNCTION_ARGS)
 
 		resstat = xsltSaveResultToString((xmlChar **) &resstr, &reslen,
 										 restree, stylesheet);
-
-		if (resstat >= 0)
-			result = cstring_to_text_with_len((char *) resstr, reslen);
+		if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt))
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY,
+						"failed to save result to string");
+		result = cstring_to_text_with_len((char *) resstr, reslen);
 	}
 	PG_CATCH();
 	{
@@ -163,6 +178,7 @@ xslt_process(PG_FUNCTION_ARGS)
 			xmlFree(resstr);
 		xsltCleanupGlobals();
 
+		xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 		pg_xml_done(xmlerrcxt, true);
 
 		PG_RE_THROW();
@@ -179,12 +195,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	if (resstr)
 		xmlFree(resstr);
 
+	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	/* XXX this is pretty dubious, really ought to throw error instead */
-	if (resstat < 0)
-		PG_RETURN_NULL();
-
 	PG_RETURN_TEXT_P(result);
 #else							/* !USE_LIBXSLT */
 
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index f7b731825f..f54828fb99 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2135,6 +2135,35 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 			 detail ? errdetail_internal("%s", detail) : 0));
 }
 
+/*
+ * Generic error handler for libxml errors and warnings.
+ * This is not used by this module, but may be useful for
+ * libxml-based libraries like libxslt, which do not support
+ * structured error handlers.
+ */
+void
+xml_generic_error_handler(void *data, const char *msg,...)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	va_list		ap;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxslt would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext");
+
+	appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+	va_start(ap, msg);
+	appendStringInfoVA(&xmlerrcxt->err_buf, msg, ap);
+	va_end(ap);
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(&xmlerrcxt->err_buf);
+}
 
 /*
  * Error handler for libxml errors and warnings
diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h
index 0d7a816b9f..7cb101e81d 100644
--- a/src/include/utils/xml.h
+++ b/src/include/utils/xml.h
@@ -66,6 +66,8 @@ extern void pg_xml_init_library(void);
 extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness);
 extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError);
 extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt);
+extern void xml_generic_error_handler(void *data, const char *msg,...)
+			pg_attribute_printf(2, 3);
 extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode,
 						const char *msg);
 
-- 
2.49.0

From bd2e6c9d4197d3f98db509ec112b6f21db97f287 Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <haberkorn@b1-systems.de>
Date: Wed, 30 Apr 2025 13:19:42 +0300
Subject: [PATCH v5 2/2] contrib/xml2: overloaded xslt_process() to provide
 variants for xmltype and specifying parameters in arrays

* There are apparently no functions that accept XML as text, except for xmlparse().
  xslt_process() should therefore also accept xmltype.
* A version accepting text is still kept for backwards compatibility, but is considered
  deprecated.
* The new xmltype-based version expects an array of stylesheet parameter-value pairs,
  which is less limited than the now deprecated way of encoding all stylesheet parameters into
  a single text argument.
  We can now accept an arbitrary number of parameters and you can include `=` and `,` signs
  in both the key and value strings.
  Hstores haven't been used since they are in a module and we don't want to depend on any
  additional module.
* The new implementation respects the database's encoding - text strings are always converted to UTF8
  before passing them into libxml2.
* On the downside, xml_parse() had to be made an external function.
  Since a declaration cannot be added to xml.h without drawing in libxml2 headers,
  the declaration is repeated in xslt_proc.c.
  Perhaps xml_parse() should be declared in a separate internal header?
* xmlCtxtReadDoc() now sets a dummy "SQL" URL to preserve line numbers in XSLT stylesheet errors.
  This change at least does not break the test suite.
---
 contrib/xml2/expected/xml2.out |  13 +++
 contrib/xml2/sql/xml2.sql      |   8 ++
 contrib/xml2/xml2--1.1.sql     |  11 +++
 contrib/xml2/xslt_proc.c       | 148 +++++++++++++++++++++++++--------
 doc/src/sgml/xml2.sgml         |  19 +++--
 src/backend/utils/adt/xml.c    |  19 +++--
 6 files changed, 172 insertions(+), 46 deletions(-)

diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out
index 157d584e63..0a8a628020 100644
--- a/contrib/xml2/expected/xml2.out
+++ b/contrib/xml2/expected/xml2.out
@@ -278,3 +278,16 @@ Variable 'n1' has not been declared.
 Undefined variable
 runtime error: file SQL line 3 element value-of
 XPath evaluation returned no result.
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
+ xslt_process 
+--------------
+ foo         +
+ 
+(1 row)
+
diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql
index 9d42ac8a0b..7555854d49 100644
--- a/contrib/xml2/sql/xml2.sql
+++ b/contrib/xml2/sql/xml2.sql
@@ -161,3 +161,11 @@ $$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
     <value-of select="$n1"/>
   </template>
 </stylesheet>$$)::xml;
+
+-- xmltype and Array-based signature
+SELECT xslt_process(xmlelement(name xml),
+$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform">
+  <template match="/">
+    <value-of select="$n1"/>
+  </template>
+</stylesheet>$$::xml, ARRAY['n1','"foo"']);
diff --git a/contrib/xml2/xml2--1.1.sql b/contrib/xml2/xml2--1.1.sql
index 671372cb27..a579a1e5e1 100644
--- a/contrib/xml2/xml2--1.1.sql
+++ b/contrib/xml2/xml2--1.1.sql
@@ -71,3 +71,14 @@ CREATE FUNCTION xslt_process(text,text)
 RETURNS text
 AS 'MODULE_PATHNAME'
 LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
+
+CREATE FUNCTION xslt_process(xml,xml,text[])
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
+
+-- the function checks for the correct argument count
+CREATE FUNCTION xslt_process(xml,xml)
+RETURNS xml
+AS 'MODULE_PATHNAME','xslt_process_xmltype'
+LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index 17776f78b5..074952cf8b 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -10,6 +10,9 @@
 #include "fmgr.h"
 #include "utils/builtins.h"
 #include "utils/xml.h"
+#include "utils/array.h"
+#include "utils/memutils.h"
+#include "mb/pg_wchar.h"
 
 #ifdef USE_LIBXSLT
 
@@ -35,9 +38,18 @@
 extern PgXmlErrorContext *pgxml_parser_init(PgXmlStrictness strictness);
 
 /* local defs */
+static xmltype *xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params);
 static const char **parse_params(text *paramstr);
 #endif							/* USE_LIBXSLT */
 
+/*
+ * FIXME: This cannot easily be exposed in xml.h.
+ * Perhaps there should be an xml-internal.h?
+ */
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 
 PG_FUNCTION_INFO_V1(xslt_process);
 
@@ -48,9 +60,103 @@ xslt_process(PG_FUNCTION_ARGS)
 
 	text	   *doct = PG_GETARG_TEXT_PP(0);
 	text	   *ssheet = PG_GETARG_TEXT_PP(1);
-	text	   *volatile result = NULL;
-	text	   *paramstr;
-	const char **params;
+	const char **params = NULL;
+	text	   *result;
+
+	if (fcinfo->nargs == 3)
+	{
+		text	   *paramstr = PG_GETARG_TEXT_PP(2);
+
+		params = parse_params(paramstr);
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_TEXT_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+PG_FUNCTION_INFO_V1(xslt_process_xmltype);
+
+Datum
+xslt_process_xmltype(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXSLT
+
+	xmltype    *doct = PG_GETARG_XML_P(0);
+	xmltype    *ssheet = PG_GETARG_XML_P(1);
+	const char **params = NULL;
+	xmltype    *result;
+
+	/*
+	 * Parameters are key-value pairs. The values are XPath expressions, so
+	 * strings will have to be escaped with single or double quotes. Even
+	 * `xsltproc --stringparam` does nothing else than adding single or double
+	 * quotes and fails if the value contains both.
+	 */
+	if (fcinfo->nargs == 3)
+	{
+		ArrayType  *paramarray = PG_GETARG_ARRAYTYPE_P(2);
+		Datum	   *arr_datums;
+		bool	   *arr_nulls;
+		int			arr_count;
+		int			i,
+					j;
+
+		deconstruct_array_builtin(paramarray, TEXTOID, &arr_datums, &arr_nulls, &arr_count);
+
+		if ((arr_count % 2) != 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_ARRAY_ELEMENT_ERROR),
+					 errmsg("number of stylesheet parameters (%d) must be a multiple of 2",
+							arr_count)));
+
+		params = palloc_array(const char *, arr_count + 1);
+
+		for (i = 0, j = 0; i < arr_count; i++)
+		{
+			char	   *cstr;
+
+			if (arr_nulls[i])
+				continue;
+
+			cstr = TextDatumGetCString(arr_datums[i]);
+			params[j++] = (char *) pg_do_encoding_conversion((unsigned char *) cstr,
+															 strlen(cstr),
+															 GetDatabaseEncoding(),
+															 PG_UTF8);
+		}
+		params[j] = NULL;
+	}
+
+	result = xslt_process_internal(doct, ssheet, params);
+
+	PG_RETURN_XML_P(result);
+
+#else							/* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif							/* USE_LIBXSLT */
+}
+
+#ifdef USE_LIBXSLT
+
+static xmltype *
+xslt_process_internal(xmltype *doct, xmltype *ssheet, const char **params)
+{
+	text	   *volatile result;
 	PgXmlErrorContext *xmlerrcxt;
 	volatile xsltStylesheetPtr stylesheet = NULL;
 	volatile xmlDocPtr doctree = NULL;
@@ -64,18 +170,6 @@ xslt_process(PG_FUNCTION_ARGS)
 	xmlGenericErrorFunc saved_errfunc;
 	void	   *saved_errcxt;
 
-	if (fcinfo->nargs == 3)
-	{
-		paramstr = PG_GETARG_TEXT_PP(2);
-		params = parse_params(paramstr);
-	}
-	else
-	{
-		/* No parameters */
-		params = (const char **) palloc(sizeof(char *));
-		params[0] = NULL;
-	}
-
 	/* Setup parser */
 	xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL);
 
@@ -93,21 +187,18 @@ xslt_process(PG_FUNCTION_ARGS)
 		int			reslen = 0;
 
 		/*
-		 * Parse document. It's important to set an "URL", so libxslt includes
-		 * line numbers in error messages (cf. xsltPrintErrorContext()).
+		 * Parse document.
 		 */
-		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
-								VARSIZE_ANY_EXHDR(doct), "SQL", NULL,
-								XML_PARSE_NOENT);
+		doctree = xml_parse(doct, XMLOPTION_DOCUMENT, true,
+							GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
-		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
-							  VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL,
-							  XML_PARSE_NOENT);
+		ssdoc = xml_parse(ssheet, XMLOPTION_DOCUMENT, true,
+						  GetDatabaseEncoding(), NULL, NULL, NULL);
 
 		if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt))
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
@@ -198,18 +289,9 @@ xslt_process(PG_FUNCTION_ARGS)
 	xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc);
 	pg_xml_done(xmlerrcxt, false);
 
-	PG_RETURN_TEXT_P(result);
-#else							/* !USE_LIBXSLT */
-
-	ereport(ERROR,
-			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			 errmsg("xslt_process() is not available without libxslt")));
-	PG_RETURN_NULL();
-#endif							/* USE_LIBXSLT */
+	return result;
 }
 
-#ifdef USE_LIBXSLT
-
 static const char **
 parse_params(text *paramstr)
 {
diff --git a/doc/src/sgml/xml2.sgml b/doc/src/sgml/xml2.sgml
index 9fd613f967..dc6fb40121 100644
--- a/doc/src/sgml/xml2.sgml
+++ b/doc/src/sgml/xml2.sgml
@@ -408,22 +408,29 @@ ORDER BY doc_num, line_num;
   </indexterm>
 
 <synopsis>
-xslt_process(text document, text stylesheet, text paramlist) returns text
+xslt_process(xml document, xml stylesheet, text[] paramlist) returns xml
 </synopsis>
 
    <para>
     This function applies the XSL stylesheet to the document and returns
-    the transformed result. The <literal>paramlist</literal> is a list of parameter
-    assignments to be used in the transformation, specified in the form
-    <literal>a=1,b=2</literal>. Note that the
-    parameter parsing is very simple-minded: parameter values cannot
-    contain commas!
+    the transformed result. The <literal>paramlist</literal> is an array of parameter
+    assignments to be used in the transformation, specified in pairs of
+    key and value strings (e.g. <literal>ARRAY['a','1', 'b','2']</literal>).
+    The length of the array must be even.
+    Note that the values are still interpreted as XPath expressions, so string values need to
+    be quoted in single or double quotes (e.g. <literal>ARRAY['a','"string"']</literal>).
    </para>
 
    <para>
     There is also a two-parameter version of <function>xslt_process</function> which
     does not pass any parameters to the transformation.
    </para>
+
+   <para>
+    <emphasis>Deprecated</emphasis> variants of <function>xslt_process</function> accepting
+    text arguments and parameters encoded into single text strings
+    (e.g. <literal>a=1,b=2</literal>) are also still available.
+   </para>
   </sect3>
  </sect2>
 
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index f54828fb99..3b8ab29555 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -155,11 +155,11 @@ static int	parse_xml_decl(const xmlChar *str, size_t *lenp,
 static bool print_xml_decl(StringInfo buf, const xmlChar *version,
 						   pg_enc encoding, int standalone);
 static bool xml_doctype_in_content(const xmlChar *str);
-static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
-						   bool preserve_whitespace, int encoding,
-						   XmlOptionType *parsed_xmloptiontype,
-						   xmlNodePtr *parsed_nodes,
-						   Node *escontext);
+xmlDocPtr	xml_parse(text *data, XmlOptionType xmloption_arg,
+					  bool preserve_whitespace, int encoding,
+					  XmlOptionType *parsed_xmloptiontype,
+					  xmlNodePtr *parsed_nodes,
+					  Node *escontext);
 static text *xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt);
 static int	xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 								   ArrayBuildState *astate,
@@ -1783,7 +1783,7 @@ xml_doctype_in_content(const xmlChar *str)
  * TODO maybe libxml2's xmlreader is better? (do not construct DOM,
  * yet do not use SAX - see xmlreader.c)
  */
-static xmlDocPtr
+xmlDocPtr
 xml_parse(text *data, XmlOptionType xmloption_arg,
 		  bool preserve_whitespace, int encoding,
 		  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
@@ -1879,8 +1879,13 @@ xml_parse(text *data, XmlOptionType xmloption_arg,
 				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
 							"could not allocate parser context");
 
+			/*
+			 * Setting a dummy "SQL" URL is important for the
+			 * xsltPrintErrorContext() when using the legacy text-based
+			 * xslt_process() variant.
+			 */
 			doc = xmlCtxtReadDoc(ctxt, utf8string,
-								 NULL,	/* no URL */
+								 "SQL",
 								 "UTF-8",
 								 options);
 
-- 
2.49.0