From 0a9ee763b22c146727d14a50da0c5bbc82e70435 Mon Sep 17 00:00:00 2001
From: Kjell Ahlstedt <kjellahlstedt@gmail.com>
Date: Mon, 27 Sep 2021 10:30:58 +0200
Subject: docs/manual, Meson config: Check if xmllint can be used

---
 Makefile.am                     |  1 +
 docs/manual/can_use_xmllint.xml | 15 +++++++++++++++
 docs/manual/meson.build         | 18 ++++++++++++++++++
 meson.build                     |  2 +-
 tools/tutorial-custom-cmd.py    | 12 +++++++++++-
 5 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 docs/manual/can_use_xmllint.xml

diff --git a/Makefile.am b/Makefile.am
index 9a6f4a8..0d9e4e1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -45,6 +45,7 @@ EXTRA_DIST = \
   meson_options.txt \
   sigc++config.h.meson \
   MSVC_NMake/meson.build \
+  docs/manual/can_use_xmllint.xml \
   docs/manual/meson.build \
   docs/reference/meson.build \
   examples/meson.build \
diff --git a/docs/manual/can_use_xmllint.xml b/docs/manual/can_use_xmllint.xml
new file mode 100644
index 0000000..8ff1b0d
--- /dev/null
+++ b/docs/manual/can_use_xmllint.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<book xmlns="http://docbook.org/ns/docbook"
+      version="5.0" xml:id="index" xml:lang="en">
+
+<title>xmllint test</title>
+
+<chapter xml:id="chapter-introduction">
+<title>Introduction</title>
+  <para>
+  This is a short DocBook V5.0 document. It can be used for testing if the installed
+  version of xmllint or a similar program can validate a DocBook V5.0 document.
+  </para>
+</chapter>
+
+</book>
diff --git a/docs/manual/meson.build b/docs/manual/meson.build
index bc98af9..d2f97b9 100644
--- a/docs/manual/meson.build
+++ b/docs/manual/meson.build
@@ -24,6 +24,24 @@ if not build_documentation
   subdir_done()
 endif
 
+# Check if xmllint can be used.
+if xmllint.found()
+  can_parse_and_validate = run_command(
+    python3, tutorial_custom_cmd, 'xmllint',
+    validate,
+    meson.current_source_dir() / 'can_use_xmllint.xml',
+    meson.current_build_dir() / 'can_use_xmllint.stamp',
+  ).returncode() == 0
+  if not can_parse_and_validate
+    # The DocBook V5.0 package is called docbook5-xml in Ubuntu,
+    # docbook5-schemas in Fedora. It may have other names in other distros.
+    warning('Can\'t validate XML file.\n' +
+      'xmllint does not support Relax NG schemas and DocBook V5.0.\n' +
+      'DocBook V5.0 support may require docbook5-xml, docbook5-schemas or a similar package.'
+    )
+  endif
+endif
+
 install_data('..' / 'index.html', install_dir: install_docdir)
 install_data('..' / 'images' / 'libsigc_logo.gif',
              '..' / 'images' / 'top.gif',
diff --git a/meson.build b/meson.build
index bc8d264..2c8b829 100644
--- a/meson.build
+++ b/meson.build
@@ -291,7 +291,7 @@ endif
 validate = get_option('validation') and can_parse_and_validate
 explain_val = ''
 if get_option('validation') and not validate
-  explain_val = ' (requires xmllint)'
+  explain_val = ' (requires xmllint with Relax NG and DocBook V5.0 support)'
 endif
 
 build_pdf = build_pdf_by_default and can_build_pdf
diff --git a/tools/tutorial-custom-cmd.py b/tools/tutorial-custom-cmd.py
index 50b6a5b..c102968 100755
--- a/tools/tutorial-custom-cmd.py
+++ b/tools/tutorial-custom-cmd.py
@@ -65,6 +65,13 @@ def xmllint():
   stamp_file_path = sys.argv[4]
 
   relax_ng_schema = 'http://docbook.org/xml/5.0/rng/docbook.rng'
+  # schematron_schema = 'http://docbook.org/xml/5.0/sch/docbook.sch'
+
+  # Validation against the Schematron schema does not work on Ubuntu 21.04:
+  # file:///usr/share/xml/docbook/schema/schematron/5.0/docbook.sch:6: element rule:
+  #   Schemas parser error : Failed to compile context expression db:firstterm[@linkend]
+  # .....
+  # Schematron schema http://docbook.org/xml/5.0/sch/docbook.sch failed to compile
 
   cmd = [
     'xmllint',
@@ -73,7 +80,10 @@ def xmllint():
     '--xinclude',
   ]
   if validate == 'true':
-    cmd += ['--relaxng', relax_ng_schema]
+    cmd += [
+      '--relaxng', relax_ng_schema,
+      #'--schematron', schematron_schema,
+    ]
   cmd += [input_xml_file]
   result = subprocess.run(cmd)
   if result.returncode:
-- 
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