Improve docs syntax checking and enable it in the meson build

From 2549adca5facd392d68545c1a61b10e1cf8d4bde Mon Sep 17 00:00:00 2001
From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Tue, 7 Oct 2025 15:18:03 +0300
Subject: [PATCH v6] Improve docs syntax checking

Move the checks out of the Makefile into a perl script that can be
called from both the Makefile and meson.build. The set of files checked
is simplified, so it is just all the sgml and xsl files found in
docs/src/sgml directory tree.

Along the way make some adjustments to .cirrus.tasks.yml to support this
better in CI.

Also ensure that the checks are run while generating the
postgres-full.xml.

Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Co-Author: Andrew Dunstan <andrew@dunslane.net>
---
 doc/src/sgml/Makefile             |  17 +---
 doc/src/sgml/docbook-test.sgml    |   9 ++
 doc/src/sgml/meson.build          |  39 +++++++-
 doc/src/sgml/sgml_syntax_check.pl | 160 ++++++++++++++++++++++++++++++
 .cirrus.tasks.yml                 |   4 +
 5 files changed, 214 insertions(+), 15 deletions(-)
 create mode 100644 doc/src/sgml/docbook-test.sgml
 create mode 100755 doc/src/sgml/sgml_syntax_check.pl

diff --git a/doc/src/sgml/Makefile b/doc/src/sgml/Makefile
index b53b2694a6b..9b6f65ad215 100644
--- a/doc/src/sgml/Makefile
+++ b/doc/src/sgml/Makefile
@@ -69,6 +69,7 @@ ALL_IMAGES := $(wildcard $(srcdir)/images/*.svg)
 # files into one big file).  This helps tools that don't understand
 # vpath builds (such as dbtoepub).
 postgres-full.xml: postgres.sgml $(ALL_SGML)
+	$(PERL) $(srcdir)/sgml_syntax_check.pl --srcdir $(srcdir)
 	$(XMLLINT) $(XMLINCLUDE) --output $@ --noent --valid $<
 
 
@@ -200,8 +201,8 @@ MAKEINFO = makeinfo
 ##
 
 # Quick syntax check without style processing
-check: postgres.sgml $(ALL_SGML) check-tabs check-nbsp
-	$(XMLLINT) $(XMLINCLUDE) --noout --valid $<
+check: postgres.sgml $(ALL_SGML)
+	$(PERL) $(srcdir)/sgml_syntax_check.pl --xmllint "$(XMLLINT)" --xmllint_input $< --srcdir $(srcdir)
 
 
 ##
@@ -261,18 +262,6 @@ clean-man:
 
 endif # sqlmansectnum != 7
 
-# tabs are harmless, but it is best to avoid them in SGML files
-check-tabs:
-	@( ! grep '	' $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl) ) || \
-	(echo "Tabs appear in SGML/XML files" 1>&2;  exit 1)
-
-# Non-breaking spaces are harmless, but it is best to avoid them in SGML files.
-# Use perl command because non-GNU grep or sed could not have hex escape sequence.
-check-nbsp:
-	@ ( $(PERL) -ne '/\xC2\xA0/ and print("$$ARGV:$$_"),$$n++; END {exit($$n>0)}' \
-	  $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl $(srcdir)/images/*.xsl) ) || \
-	(echo "Non-breaking spaces appear in SGML/XML files" 1>&2;  exit 1)
-
 ##
 ## Clean
 ##
diff --git a/doc/src/sgml/docbook-test.sgml b/doc/src/sgml/docbook-test.sgml
new file mode 100644
index 00000000000..242a52676e0
--- /dev/null
+++ b/doc/src/sgml/docbook-test.sgml
@@ -0,0 +1,9 @@
+<!-- doc/src/sgml/docbook-test.sgml -->
+
+<!-- This file is used to check if the DocBook can be found -->
+
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<book>
+  <title>DocBook Test</title>
+</book>
diff --git a/doc/src/sgml/meson.build b/doc/src/sgml/meson.build
index 6ae192eac68..e5b7e58f6ad 100644
--- a/doc/src/sgml/meson.build
+++ b/doc/src/sgml/meson.build
@@ -96,6 +96,26 @@ xmllint = xmltools_wrapper + [
   '--tool', xmllint_bin, '--',
 ]
 
+sgml_syntax_check = files(
+  'sgml_syntax_check.pl'
+)
+
+# Create a stamp file for sgml syntax check and make postgres_full_xml
+# depend on it.  So, this check will run before the generation of
+# postgres_full_xml.
+sgml_check_stamp = custom_target('sgml-check-stamp',
+  output: 'sgml-check-stamp',
+  depfile: 'sgml-check-stamp.d',
+  command: [
+    perl, sgml_syntax_check,
+    '--srcdir', meson.current_source_dir(),
+    '--builddir', meson.current_build_dir(),
+    '--dep_file', '@DEPFILE@',
+    '--stamp_file', '@OUTPUT@',
+  ],
+  build_by_default: false,
+)
+
 # Run validation only once, common to all subsequent targets.  While
 # we're at it, also resolve all entities (that is, copy all included
 # files into one big file).  This helps tools that don't understand
@@ -106,7 +126,7 @@ postgres_full_xml = custom_target('postgres-full.xml',
   depfile: 'postgres-full.xml.d',
   command: [xmllint, '--nonet', '--noent', '--valid',
             '--path', '@OUTDIR@', '-o', '@OUTPUT@', '@INPUT@'],
-  depends: doc_generated,
+  depends: [doc_generated, sgml_check_stamp],
   build_by_default: false,
 )
 docs += postgres_full_xml
@@ -306,3 +326,20 @@ endif
 if alldocs.length() != 0
   alias_target('alldocs', alldocs)
 endif
+
+test(
+  'sgml_syntax_check',
+  perl,
+  protocol: 'exitcode',
+  suite: 'doc',
+  args: [
+    sgml_syntax_check,
+    '--srcdir', meson.current_source_dir(),
+    '--builddir', meson.current_build_dir(),
+    '--xmllint', '@0@ --nonet'.format(xmllint_bin.full_path()),
+    '--xmllint_input', 'postgres.sgml'
+  ],
+  depends: doc_generated
+)
+
+testprep_targets += doc_generated
diff --git a/doc/src/sgml/sgml_syntax_check.pl b/doc/src/sgml/sgml_syntax_check.pl
new file mode 100755
index 00000000000..8748a42cc99
--- /dev/null
+++ b/doc/src/sgml/sgml_syntax_check.pl
@@ -0,0 +1,160 @@
+#!/usr/bin/perl
+#
+# Perl script that checks SGML/XSL syntax and formatting issues.
+#
+# doc/src/sgml/sgml_syntax_check.pl
+#
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+use Getopt::Long;
+
+use File::Find;
+
+my $srcdir;
+my $builddir;
+my $xmllint;
+my $xmllint_input;
+my $dep_file;
+my $stamp_file;
+
+GetOptions(
+	'srcdir:s' => \$srcdir,
+	'builddir:s' => \$builddir,
+	'xmllint:s' => \$xmllint,
+	'xmllint_input:s' => \$xmllint_input,
+	'dep_file:s' => \$dep_file,
+	'stamp_file:s' => \$stamp_file) or die "$0: wrong arguments";
+
+die "$0: --srcdir must be specified\n" unless defined $srcdir;
+
+my $xmlinclude = "--path . --path $srcdir";
+$xmlinclude .= " --path $builddir" if defined $builddir;
+
+# Find files to process - all the sgml and xsl files (including in subdirectories)
+my @files_to_process;
+my @dirs_to_search = ($srcdir);
+push @dirs_to_search, $builddir if defined $builddir;
+find(
+	sub {
+		return unless -f $_;
+		return if $_ !~ /\.(sgml|xsl)$/;
+		push @files_to_process, $File::Find::name;
+	},
+	@dirs_to_search,);
+
+# tabs and non-breaking spaces are harmless, but it is best to avoid them in SGML files
+sub check_tabs_and_nbsp
+{
+	my $errors = 0;
+	for my $f (@files_to_process)
+	{
+		open my $fh, "<:encoding(UTF-8)", $f or die "Can't open $f: $!";
+		my $line_no = 0;
+		while (<$fh>)
+		{
+			$line_no++;
+			if (/\t/)
+			{
+				print STDERR "Tab found in $f:$line_no\n";
+				$errors++;
+			}
+			if (/\xC2\xA0/)
+			{
+				print STDERR "$f:$line_no: contains non-breaking space\n";
+				$errors++;
+			}
+		}
+		close($fh);
+	}
+
+	if ($errors)
+	{
+		remove_stamp_file();
+		die "Tabs and/or non-breaking spaces appear in SGML/XML files\n";
+	}
+}
+
+sub test_docbook
+{
+	my $cmd = "$xmllint $xmlinclude --noout --valid docbook-test.sgml";
+	if (system($cmd) != 0)
+	{
+		remove_stamp_file();
+
+		print STDERR "DocBook DTD file can not be found\n";
+		# Exit code 77 is used for skipping the test instead of failing it
+		exit(77);
+	}
+}
+
+sub run_xmllint
+{
+	# Check DocBook DTD file before running xmllint
+	test_docbook();
+
+	my $cmd = "$xmllint $xmlinclude --noout --valid $xmllint_input";
+	my $res = system($cmd);
+	if ($res != 0)
+	{
+		remove_stamp_file();
+		die "xmllint validation failed\n";
+	}
+}
+
+sub write_dep_file()
+{
+	if ($dep_file)
+	{
+		open my $fh, '>', $dep_file or die "can't open $dep_file: $!";
+
+		foreach my $file (@files_to_process)
+		{
+			print $fh "$dep_file : $file\n";
+		}
+
+		close $fh;
+	}
+}
+
+sub create_stamp_file
+{
+	# All checks are passed, we can create a stamp file now
+	if ($stamp_file)
+	{
+		# Avoid touching existing stamp file to prevent unnecessary rebuilds
+		if (!(-f $stamp_file))
+		{
+			open my $fh, '>', $stamp_file
+			  or die "can't open $stamp_file: $!";
+			close $fh;
+		}
+
+	}
+}
+
+sub remove_stamp_file
+{
+	if ($stamp_file)
+	{
+		unlink $stamp_file;
+	}
+}
+
+# Create a dependency file for meson build
+write_dep_file();
+
+### Do the checks
+check_tabs_and_nbsp();
+
+# Run xmllint check only if its arguments are passed. Because generation of
+# postgres-full.xml already does xmllint check, we don't want to do this check
+# twice.
+if ($xmllint && $xmllint_input)
+{
+	run_xmllint();
+}
+###
+
+create_stamp_file();
diff --git a/.cirrus.tasks.yml b/.cirrus.tasks.yml
index eca9d62fc22..701a508e396 100644
--- a/.cirrus.tasks.yml
+++ b/.cirrus.tasks.yml
@@ -627,6 +627,9 @@ task:
     TEST_JOBS: 8
     IMAGE: ghcr.io/cirruslabs/macos-runner:sonoma
 
+    # Ensure DocBook 4.5 DTD is available for syntax checks
+    XML_CATALOG_FILES: /opt/local/share/xml/docbook/4.5/catalog.xml
+
     CIRRUS_WORKING_DIR: ${HOME}/pgsql/
     CCACHE_DIR: ${HOME}/ccache
     MACPORTS_CACHE: ${HOME}/macports-cache
@@ -641,6 +644,7 @@ task:
 
     MACOS_PACKAGE_LIST: >-
       ccache
+      docbook-xml-4.5
       icu
       kerberos5
       lz4
-- 
2.51.0

From bab59770eee6ee348d20c8cb7eb1b7af5366f5df Mon Sep 17 00:00:00 2001
From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Tue, 21 Oct 2025 13:49:16 +0300
Subject: [PATCH v7] Improve docs syntax checking

Move the checks out of the Makefile into a perl script that can be
called from both the Makefile and meson.build. The set of files checked
is simplified, so it is just all the sgml and xsl files found in
docs/src/sgml directory tree.

Along the way make some adjustments to .cirrus.tasks.yml to support this
better in CI.

Also ensure that the checks are run while generating the
postgres-full.xml.

Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Co-Author: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CAN55FZ1qzoDcaKqsR3DwE%3DX6FL%2Bwpm%2B%3DKLvH6ahrRXNhjU53DQ%40mail.gmail.com
---
 doc/src/sgml/Makefile             |  16 +----
 doc/src/sgml/meson.build          |  34 ++++++++-
 doc/src/sgml/sgml_syntax_check.pl | 115 ++++++++++++++++++++++++++++++
 .cirrus.tasks.yml                 |   3 +
 4 files changed, 153 insertions(+), 15 deletions(-)
 create mode 100755 doc/src/sgml/sgml_syntax_check.pl

diff --git a/doc/src/sgml/Makefile b/doc/src/sgml/Makefile
index b53b2694a6b..50de8fab931 100644
--- a/doc/src/sgml/Makefile
+++ b/doc/src/sgml/Makefile
@@ -69,6 +69,7 @@ ALL_IMAGES := $(wildcard $(srcdir)/images/*.svg)
 # files into one big file).  This helps tools that don't understand
 # vpath builds (such as dbtoepub).
 postgres-full.xml: postgres.sgml $(ALL_SGML)
+	$(PERL) $(srcdir)/sgml_syntax_check.pl --srcdir $(srcdir)
 	$(XMLLINT) $(XMLINCLUDE) --output $@ --noent --valid $<
 
 
@@ -200,8 +201,7 @@ MAKEINFO = makeinfo
 ##
 
 # Quick syntax check without style processing
-check: postgres.sgml $(ALL_SGML) check-tabs check-nbsp
-	$(XMLLINT) $(XMLINCLUDE) --noout --valid $<
+check: postgres-full.xml
 
 
 ##
@@ -261,18 +261,6 @@ clean-man:
 
 endif # sqlmansectnum != 7
 
-# tabs are harmless, but it is best to avoid them in SGML files
-check-tabs:
-	@( ! grep '	' $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl) ) || \
-	(echo "Tabs appear in SGML/XML files" 1>&2;  exit 1)
-
-# Non-breaking spaces are harmless, but it is best to avoid them in SGML files.
-# Use perl command because non-GNU grep or sed could not have hex escape sequence.
-check-nbsp:
-	@ ( $(PERL) -ne '/\xC2\xA0/ and print("$$ARGV:$$_"),$$n++; END {exit($$n>0)}' \
-	  $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl $(srcdir)/images/*.xsl) ) || \
-	(echo "Non-breaking spaces appear in SGML/XML files" 1>&2;  exit 1)
-
 ##
 ## Clean
 ##
diff --git a/doc/src/sgml/meson.build b/doc/src/sgml/meson.build
index 6ae192eac68..7895ae5e776 100644
--- a/doc/src/sgml/meson.build
+++ b/doc/src/sgml/meson.build
@@ -96,6 +96,26 @@ xmllint = xmltools_wrapper + [
   '--tool', xmllint_bin, '--',
 ]
 
+sgml_syntax_check = files(
+  'sgml_syntax_check.pl'
+)
+
+# Create a stamp file for sgml syntax check and make postgres_full_xml
+# depend on it.  So, this check will run before the generation of
+# postgres_full_xml.
+sgml_check_stamp = custom_target('sgml-check-stamp',
+  output: 'sgml-check-stamp',
+  depfile: 'sgml-check-stamp.d',
+  command: [
+    perl, sgml_syntax_check,
+    '--srcdir', meson.current_source_dir(),
+    '--builddir', meson.current_build_dir(),
+    '--dep_file', '@DEPFILE@',
+    '--stamp_file', '@OUTPUT@',
+  ],
+  build_by_default: false,
+)
+
 # Run validation only once, common to all subsequent targets.  While
 # we're at it, also resolve all entities (that is, copy all included
 # files into one big file).  This helps tools that don't understand
@@ -106,7 +126,7 @@ postgres_full_xml = custom_target('postgres-full.xml',
   depfile: 'postgres-full.xml.d',
   command: [xmllint, '--nonet', '--noent', '--valid',
             '--path', '@OUTDIR@', '-o', '@OUTPUT@', '@INPUT@'],
-  depends: doc_generated,
+  depends: [doc_generated, sgml_check_stamp],
   build_by_default: false,
 )
 docs += postgres_full_xml
@@ -306,3 +326,15 @@ endif
 if alldocs.length() != 0
   alias_target('alldocs', alldocs)
 endif
+
+# Test creation of 'postgres_full_xml' by depending on it.
+test(
+  'doc' / 'sgml_syntax_check',
+  # We actually don't need to set 'executable', as we run the test by depending
+  # on 'postgres_full_xml', but meson requires setting an executable.
+  perl,
+  suite: 'doc',
+  depends: postgres_full_xml
+)
+
+testprep_targets += doc_generated
diff --git a/doc/src/sgml/sgml_syntax_check.pl b/doc/src/sgml/sgml_syntax_check.pl
new file mode 100755
index 00000000000..55c212d9e5d
--- /dev/null
+++ b/doc/src/sgml/sgml_syntax_check.pl
@@ -0,0 +1,115 @@
+#!/usr/bin/perl
+#
+# Perl script that checks SGML/XSL syntax and formatting issues.
+#
+# doc/src/sgml/sgml_syntax_check.pl
+#
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+use Getopt::Long;
+
+use File::Find;
+
+my $srcdir;
+my $builddir;
+my $dep_file;
+my $stamp_file;
+
+GetOptions(
+	'srcdir:s' => \$srcdir,
+	'builddir:s' => \$builddir,
+	'dep_file:s' => \$dep_file,
+	'stamp_file:s' => \$stamp_file) or die "$0: wrong arguments";
+
+die "$0: --srcdir must be specified\n" unless defined $srcdir;
+
+# Find files to process - all the sgml and xsl files (including in subdirectories)
+my @files_to_process;
+my @dirs_to_search = ($srcdir);
+push @dirs_to_search, $builddir if defined $builddir;
+find(
+	sub {
+		return unless -f $_;
+		return if $_ !~ /\.(sgml|xsl)$/;
+		push @files_to_process, $File::Find::name;
+	},
+	@dirs_to_search,);
+
+# tabs and non-breaking spaces are harmless, but it is best to avoid them in SGML files
+sub check_tabs_and_nbsp
+{
+	my $errors = 0;
+	for my $f (@files_to_process)
+	{
+		open my $fh, "<:encoding(UTF-8)", $f or die "Can't open $f: $!";
+		my $line_no = 0;
+		while (<$fh>)
+		{
+			$line_no++;
+			if (/\t/)
+			{
+				print STDERR "Tab found in $f:$line_no\n";
+				$errors++;
+			}
+			if (/\xC2\xA0/)
+			{
+				print STDERR "$f:$line_no: contains non-breaking space\n";
+				$errors++;
+			}
+		}
+		close($fh);
+	}
+
+	if ($errors)
+	{
+		remove_stamp_file();
+		die "Tabs and/or non-breaking spaces appear in SGML/XML files\n";
+	}
+}
+
+sub write_dep_file()
+{
+	open my $fh, '>', $dep_file or die "can't open $dep_file: $!";
+
+	foreach my $file (@files_to_process)
+	{
+		print $fh "$dep_file : $file\n";
+	}
+
+	close $fh;
+}
+
+sub create_stamp_file
+{
+	# Avoid touching existing stamp file to prevent unnecessary rebuilds
+	if (!(-f $stamp_file))
+	{
+		open my $fh, '>', $stamp_file
+		  or die "can't open $stamp_file: $!";
+		close $fh;
+	}
+}
+
+sub remove_stamp_file
+{
+	if ($stamp_file)
+	{
+		unlink $stamp_file;
+	}
+}
+
+# Create a dependency file for meson build
+if ($dep_file)
+{
+	write_dep_file();
+}
+
+check_tabs_and_nbsp();
+
+# All checks are passed, we can create a stamp file meson build now
+if ($stamp_file)
+{
+	create_stamp_file();
+}
diff --git a/.cirrus.tasks.yml b/.cirrus.tasks.yml
index eca9d62fc22..1c937247a9a 100644
--- a/.cirrus.tasks.yml
+++ b/.cirrus.tasks.yml
@@ -627,6 +627,8 @@ task:
     TEST_JOBS: 8
     IMAGE: ghcr.io/cirruslabs/macos-runner:sonoma
 
+    XML_CATALOG_FILES: /opt/local/share/xml/docbook/4.5/catalog.xml
+
     CIRRUS_WORKING_DIR: ${HOME}/pgsql/
     CCACHE_DIR: ${HOME}/ccache
     MACPORTS_CACHE: ${HOME}/macports-cache
@@ -641,6 +643,7 @@ task:
 
     MACOS_PACKAGE_LIST: >-
       ccache
+      docbook-xml-4.5
       icu
       kerberos5
       lz4
-- 
2.51.0

From c313f86470c51300319fa9e4c2f3f541d7dc0c47 Mon Sep 17 00:00:00 2001
From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Tue, 21 Oct 2025 13:49:16 +0300
Subject: [PATCH v8] Improve docs syntax checking

Move the checks out of the Makefile into a perl script that can be
called from both the Makefile and meson.build. The set of files checked
is simplified, so it is just all the sgml and xsl files found in
docs/src/sgml directory tree.

Along the way make some adjustments to .cirrus.tasks.yml to support this
better in CI.

Also ensure that the checks are run while generating the
postgres-full.xml.

Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Co-Author: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CAN55FZ1qzoDcaKqsR3DwE%3DX6FL%2Bwpm%2B%3DKLvH6ahrRXNhjU53DQ%40mail.gmail.com
---
 doc/src/sgml/Makefile             |  16 +----
 doc/src/sgml/meson.build          |  35 ++++++++-
 doc/src/sgml/sgml_syntax_check.pl | 115 ++++++++++++++++++++++++++++++
 .cirrus.tasks.yml                 |   3 +
 4 files changed, 154 insertions(+), 15 deletions(-)
 create mode 100755 doc/src/sgml/sgml_syntax_check.pl

diff --git a/doc/src/sgml/Makefile b/doc/src/sgml/Makefile
index b53b2694a6b..50de8fab931 100644
--- a/doc/src/sgml/Makefile
+++ b/doc/src/sgml/Makefile
@@ -69,6 +69,7 @@ ALL_IMAGES := $(wildcard $(srcdir)/images/*.svg)
 # files into one big file).  This helps tools that don't understand
 # vpath builds (such as dbtoepub).
 postgres-full.xml: postgres.sgml $(ALL_SGML)
+	$(PERL) $(srcdir)/sgml_syntax_check.pl --srcdir $(srcdir)
 	$(XMLLINT) $(XMLINCLUDE) --output $@ --noent --valid $<
 
 
@@ -200,8 +201,7 @@ MAKEINFO = makeinfo
 ##
 
 # Quick syntax check without style processing
-check: postgres.sgml $(ALL_SGML) check-tabs check-nbsp
-	$(XMLLINT) $(XMLINCLUDE) --noout --valid $<
+check: postgres-full.xml
 
 
 ##
@@ -261,18 +261,6 @@ clean-man:
 
 endif # sqlmansectnum != 7
 
-# tabs are harmless, but it is best to avoid them in SGML files
-check-tabs:
-	@( ! grep '	' $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl) ) || \
-	(echo "Tabs appear in SGML/XML files" 1>&2;  exit 1)
-
-# Non-breaking spaces are harmless, but it is best to avoid them in SGML files.
-# Use perl command because non-GNU grep or sed could not have hex escape sequence.
-check-nbsp:
-	@ ( $(PERL) -ne '/\xC2\xA0/ and print("$$ARGV:$$_"),$$n++; END {exit($$n>0)}' \
-	  $(wildcard $(srcdir)/*.sgml $(srcdir)/func/*.sgml $(srcdir)/ref/*.sgml $(srcdir)/*.xsl $(srcdir)/images/*.xsl) ) || \
-	(echo "Non-breaking spaces appear in SGML/XML files" 1>&2;  exit 1)
-
 ##
 ## Clean
 ##
diff --git a/doc/src/sgml/meson.build b/doc/src/sgml/meson.build
index 6ae192eac68..6ffe4110167 100644
--- a/doc/src/sgml/meson.build
+++ b/doc/src/sgml/meson.build
@@ -96,6 +96,26 @@ xmllint = xmltools_wrapper + [
   '--tool', xmllint_bin, '--',
 ]
 
+sgml_syntax_check = files(
+  'sgml_syntax_check.pl'
+)
+
+# Create a stamp file for sgml syntax check and make postgres_full_xml
+# depend on it.  So, this check will run before the generation of
+# postgres_full_xml.
+sgml_check_stamp = custom_target('sgml-check-stamp',
+  output: 'sgml-check-stamp',
+  depfile: 'sgml-check-stamp.d',
+  command: [
+    perl, sgml_syntax_check,
+    '--srcdir', meson.current_source_dir(),
+    '--builddir', meson.current_build_dir(),
+    '--dep_file', '@DEPFILE@',
+    '--stamp_file', '@OUTPUT@',
+  ],
+  build_by_default: false,
+)
+
 # Run validation only once, common to all subsequent targets.  While
 # we're at it, also resolve all entities (that is, copy all included
 # files into one big file).  This helps tools that don't understand
@@ -106,12 +126,15 @@ postgres_full_xml = custom_target('postgres-full.xml',
   depfile: 'postgres-full.xml.d',
   command: [xmllint, '--nonet', '--noent', '--valid',
             '--path', '@OUTDIR@', '-o', '@OUTPUT@', '@INPUT@'],
-  depends: doc_generated,
+  depends: [doc_generated, sgml_check_stamp],
   build_by_default: false,
 )
 docs += postgres_full_xml
 alldocs += postgres_full_xml
 
+postgres_full_xml_target = 'postgres_full_xml'
+alias_target(postgres_full_xml_target, postgres_full_xml)
+
 
 if xsltproc_bin.found()
   xsltproc_flags = [
@@ -306,3 +329,13 @@ endif
 if alldocs.length() != 0
   alias_target('alldocs', alldocs)
 endif
+
+# Test creation of 'postgres_full_xml'.
+test(
+  'doc' / 'sgml_syntax_check',
+  meson_bin,
+  args: ['compile', postgres_full_xml_target],
+  suite: 'doc'
+)
+
+testprep_targets += doc_generated
diff --git a/doc/src/sgml/sgml_syntax_check.pl b/doc/src/sgml/sgml_syntax_check.pl
new file mode 100755
index 00000000000..55c212d9e5d
--- /dev/null
+++ b/doc/src/sgml/sgml_syntax_check.pl
@@ -0,0 +1,115 @@
+#!/usr/bin/perl
+#
+# Perl script that checks SGML/XSL syntax and formatting issues.
+#
+# doc/src/sgml/sgml_syntax_check.pl
+#
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+use Getopt::Long;
+
+use File::Find;
+
+my $srcdir;
+my $builddir;
+my $dep_file;
+my $stamp_file;
+
+GetOptions(
+	'srcdir:s' => \$srcdir,
+	'builddir:s' => \$builddir,
+	'dep_file:s' => \$dep_file,
+	'stamp_file:s' => \$stamp_file) or die "$0: wrong arguments";
+
+die "$0: --srcdir must be specified\n" unless defined $srcdir;
+
+# Find files to process - all the sgml and xsl files (including in subdirectories)
+my @files_to_process;
+my @dirs_to_search = ($srcdir);
+push @dirs_to_search, $builddir if defined $builddir;
+find(
+	sub {
+		return unless -f $_;
+		return if $_ !~ /\.(sgml|xsl)$/;
+		push @files_to_process, $File::Find::name;
+	},
+	@dirs_to_search,);
+
+# tabs and non-breaking spaces are harmless, but it is best to avoid them in SGML files
+sub check_tabs_and_nbsp
+{
+	my $errors = 0;
+	for my $f (@files_to_process)
+	{
+		open my $fh, "<:encoding(UTF-8)", $f or die "Can't open $f: $!";
+		my $line_no = 0;
+		while (<$fh>)
+		{
+			$line_no++;
+			if (/\t/)
+			{
+				print STDERR "Tab found in $f:$line_no\n";
+				$errors++;
+			}
+			if (/\xC2\xA0/)
+			{
+				print STDERR "$f:$line_no: contains non-breaking space\n";
+				$errors++;
+			}
+		}
+		close($fh);
+	}
+
+	if ($errors)
+	{
+		remove_stamp_file();
+		die "Tabs and/or non-breaking spaces appear in SGML/XML files\n";
+	}
+}
+
+sub write_dep_file()
+{
+	open my $fh, '>', $dep_file or die "can't open $dep_file: $!";
+
+	foreach my $file (@files_to_process)
+	{
+		print $fh "$dep_file : $file\n";
+	}
+
+	close $fh;
+}
+
+sub create_stamp_file
+{
+	# Avoid touching existing stamp file to prevent unnecessary rebuilds
+	if (!(-f $stamp_file))
+	{
+		open my $fh, '>', $stamp_file
+		  or die "can't open $stamp_file: $!";
+		close $fh;
+	}
+}
+
+sub remove_stamp_file
+{
+	if ($stamp_file)
+	{
+		unlink $stamp_file;
+	}
+}
+
+# Create a dependency file for meson build
+if ($dep_file)
+{
+	write_dep_file();
+}
+
+check_tabs_and_nbsp();
+
+# All checks are passed, we can create a stamp file meson build now
+if ($stamp_file)
+{
+	create_stamp_file();
+}
diff --git a/.cirrus.tasks.yml b/.cirrus.tasks.yml
index eca9d62fc22..1c937247a9a 100644
--- a/.cirrus.tasks.yml
+++ b/.cirrus.tasks.yml
@@ -627,6 +627,8 @@ task:
     TEST_JOBS: 8
     IMAGE: ghcr.io/cirruslabs/macos-runner:sonoma
 
+    XML_CATALOG_FILES: /opt/local/share/xml/docbook/4.5/catalog.xml
+
     CIRRUS_WORKING_DIR: ${HOME}/pgsql/
     CCACHE_DIR: ${HOME}/ccache
     MACPORTS_CACHE: ${HOME}/macports-cache
@@ -641,6 +643,7 @@ task:
 
     MACOS_PACKAGE_LIST: >-
       ccache
+      docbook-xml-4.5
       icu
       kerberos5
       lz4
-- 
2.51.0