From 74253f4b72391166834568b5b07e393dc80b72cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Prpi=C4=8D?= <mprpic@redhat.com>
Date: Mon, 29 Jun 2026 15:34:57 -0400
Subject: [PATCH] Make saxonche an optional dependency
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

saxonche (Saxon/C XSLT processor bindings) is only needed for Schematron
validation but is declared as a hard dependency, which means it is always
installed.

This is problematic becaus saxonche does not have a source distribution
on PyPI, does not publish wheels for ppc64le or s390x architectures, and
uses a non-standard git forge
(https://saxonica.plan.io/projects/saxonmirrorhe/repository); the mirror
at https://github.com/Saxonica/Saxon-HE does not publish any build
infrastructure. All of this means makes doclang uninstallable on the
aforementioned architectures or systems that require building
dependencies from source.

This changes moves saxonche from core dependencies to an optional extra
(pip install doclang[schematron]) and lazy-load it in the two functions
that use it. All other doclang functionality (packaging, XSD validation,
serialization, deserialization) works without saxonche installed.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Martin Prpič <mprpic@redhat.com>
---
 doclang/schematron_validation.py | 15 ++++++++++++++-
 pyproject.toml                   |  4 +++-
 uv.lock                          |  9 +++++++--
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/doclang/schematron_validation.py b/doclang/schematron_validation.py
index 4a241f5..bacc741 100644
--- a/doclang/schematron_validation.py
+++ b/doclang/schematron_validation.py
@@ -10,7 +10,6 @@
 from typing import Union
 
 from lxml import etree
-from saxonche import PySaxonProcessor
 
 from doclang._schemas import _bundled_sch_path
 from doclang.utils import _ensure_namespace
@@ -117,6 +116,13 @@ def _transpile_schematron_to_xslt(sch_file, verbose=False):
     if verbose:
         print(f"Transpiling Schematron: {sch_file}")
 
+    try:
+        from saxonche import PySaxonProcessor
+    except ImportError:
+        raise ImportError(
+            "saxonche is required for Schematron validation. Install it with: pip install doclang[schematron]"
+        ) from None
+
     with PySaxonProcessor(license=False) as proc:
         xslt_proc = proc.new_xslt30_processor()
 
@@ -162,6 +168,13 @@ def _validate_with_schematron(
             tmp_xml_path = tmp.name
 
             # File is still open but flushed, Saxon can read it
+            try:
+                from saxonche import PySaxonProcessor
+            except ImportError:
+                raise ImportError(
+                    "saxonche is required for Schematron validation. Install it with: pip install doclang[schematron]"
+                ) from None
+
             with PySaxonProcessor(license=False) as proc:
                 if verbose:
                     print(f"Using XSLT processor version: {proc.version}")
diff --git a/pyproject.toml b/pyproject.toml
index 6c0c942..14aaebe 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,10 +25,12 @@ classifiers = [
 ]
 dependencies = [
     "lxml>=6.0.2",
-    "saxonche>=12.9.0",
     "typer>=0.15.1",
 ]
 
+[project.optional-dependencies]
+schematron = ["saxonche>=12.9.0"]
+
 [project.urls]
 Homepage = "https://www.doclang.ai/"
 Documentation = "https://github.com/doclang-project/doclang/blob/main/README.md"
diff --git a/uv.lock b/uv.lock
index 55578d9..b8cf057 100644
--- a/uv.lock
+++ b/uv.lock
@@ -355,10 +355,14 @@ version = "0.7.0"
 source = { editable = "." }
 dependencies = [
     { name = "lxml" },
-    { name = "saxonche" },
     { name = "typer" },
 ]
 
+[package.optional-dependencies]
+schematron = [
+    { name = "saxonche" },
+]
+
 [package.dev-dependencies]
 ci = [
     { name = "mypy" },
@@ -382,9 +386,10 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "lxml", specifier = ">=6.0.2" },
-    { name = "saxonche", specifier = ">=12.9.0" },
+    { name = "saxonche", marker = "extra == 'schematron'", specifier = ">=12.9.0" },
     { name = "typer", specifier = ">=0.15.1" },
 ]
+provides-extras = ["schematron"]
 
 [package.metadata.requires-dev]
 ci = [