python3.12-lxml/Make-the-validation-of-ISO-Schematron-files-optional.patch

From a500f721e3b34018f0a86af275427663dc337b5a Mon Sep 17 00:00:00 2001
From: Stefan Behnel <stefan_ml@behnel.de>
Date: Wed, 12 Jul 2023 16:59:07 +0200
Subject: [PATCH] Make the validation of ISO-Schematron files optional in lxml,
 depending on the availability of the RNG validation file. Some lxml
 distributions discard the validation schema file due to licensing issues.

See https://bugs.launchpad.net/lxml/+bug/2024343
---
 CHANGES.txt                        | 11 +++++++++++
 doc/validation.txt                 |  9 +++++++++
 src/lxml/isoschematron/__init__.py | 24 +++++++++++++++++++-----
 3 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 24052db..e68ee9a 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -2,6 +2,17 @@
 lxml changelog
 ==============
 
+4.9.3+
+======
+
+* LP#2024343: The validation of the schema file itself is now optional in the
+  ISO-Schematron implementation.  This was done because some lxml distributions
+  discard the RNG validation schema file due to licensing issues.  The validation
+  can now always be disabled with ``Schematron(..., validate_schema=False)``.
+  It is enabled by default if available and disabled otherwise.  The module
+  constant ``lxml.isoschematron.schematron_schema_valid_supported`` can be used
+  to detect whether schema file validation is available.
+
 4.9.3 (2023-07-05)
 ==================
 
diff --git a/doc/validation.txt b/doc/validation.txt
index af9d007..27c0ccd 100644
--- a/doc/validation.txt
+++ b/doc/validation.txt
@@ -615,6 +615,15 @@ The usage of validation phases is a unique feature of ISO-Schematron and can be
 a very powerful tool e.g. for establishing validation stages or to provide 
 different validators for different "validation audiences".
 
+Note: Some lxml distributions exclude the validation schema file due to licensing issues.
+Since lxml 4.9.2-8, the validation of the user provided schema can be disabled with
+``Schematron(..., validate_schema=False)``.
+It is enabled by default if available and disabled otherwise.  Previous versions of
+lxml always had it enabled and failed at import time if the file was not available.
+Thus, some distributions chose to remove the entire ISO-Schematron support.
+The module constant ``lxml.isoschematron.schematron_schema_valid_supported`` can be used
+since lxml 4.9.2-8 to detect whether schema file validation is available.
+
 (Pre-ISO-Schematron)
 --------------------
 
diff --git a/src/lxml/isoschematron/__init__.py b/src/lxml/isoschematron/__init__.py
index 5967b10..2846a66 100644
--- a/src/lxml/isoschematron/__init__.py
+++ b/src/lxml/isoschematron/__init__.py
@@ -61,10 +61,16 @@ iso_svrl_for_xslt1 = _etree.XSLT(_etree.parse(
 svrl_validation_errors = _etree.XPath(
     '//svrl:failed-assert', namespaces={'svrl': SVRL_NS})
 
-
 # RelaxNG validator for schematron schemas
-schematron_schema_valid = _etree.RelaxNG(
-    file=os.path.join(_resources_dir, 'rng', 'iso-schematron.rng'))
+schematron_schema_valid_supported = False
+try:
+    schematron_schema_valid = _etree.RelaxNG(
+        file=os.path.join(_resources_dir, 'rng', 'iso-schematron.rng'))
+    schematron_schema_valid_supported = True
+except _etree.RelaxNGParseError:
+    # Some distributions delete the file due to licensing issues.
+    def schematron_schema_valid(arg):
+        raise NotImplementedError("Validating the ISO schematron requires iso-schematron.rng")
 
 
 def stylesheet_params(**kwargs):
@@ -153,6 +159,13 @@ class Schematron(_etree._Validator):
     report document gets stored and can be accessed as the ``validation_report``
     property.
 
+    If ``validate_schema`` is set to False, the validation of the schema file
+    itself is disabled.  Validation happens by default after building the full
+    schema, unless the schema validation file cannot be found at import time,
+    in which case the validation gets disabled.  Some lxml distributions exclude
+    this file due to licensing issues.  ISO-Schematron validation can then still
+    be used normally, but the schemas themselves cannot be validated.
+
     Here is a usage example::
 
       >>> from lxml import etree
@@ -234,7 +247,8 @@ class Schematron(_etree._Validator):
     def __init__(self, etree=None, file=None, include=True, expand=True,
                  include_params={}, expand_params={}, compile_params={},
                  store_schematron=False, store_xslt=False, store_report=False,
-                 phase=None, error_finder=ASSERTS_ONLY):
+                 phase=None, error_finder=ASSERTS_ONLY,
+                 validate_schema=schematron_schema_valid_supported):
         super(Schematron, self).__init__()
 
         self._store_report = store_report
@@ -273,7 +287,7 @@ class Schematron(_etree._Validator):
             schematron = self._include(schematron, **include_params)
         if expand:
             schematron = self._expand(schematron, **expand_params)
-        if not schematron_schema_valid(schematron):
+        if validate_schema and not schematron_schema_valid(schematron):
             raise _etree.SchematronParseError(
                 "invalid schematron schema: %s" %
                 schematron_schema_valid.error_log)
-- 
2.40.1