Work around beartype + myst-parser issue

Works around executablebooks/MyST-Parser#1017.

pyproject.toml

@@ -39,6 +39,7 @@ dynamic = [
 dependencies = [
     "beartype>=0.18.5",
     "docutils>=0.19",
+    "myst-parser>=4.0.0",
     "sphinx>=7.3.5",
 ]
 optional-dependencies.dev = [
@@ -51,7 +52,6 @@ optional-dependencies.dev = [
     "interrogate==1.7.0",
     "mypy[faster-cache]==1.14.1",
     "mypy-strict-kwargs==2024.12.25",
-    "myst-parser==4.0.0",
     "pre-commit==4.0.1",
     "pyenchant==3.3.0rc1",
     "pylint==3.3.3",

src/sphinx_substitution_extensions/__init__.py

@@ -10,6 +10,7 @@
 from docutils.parsers.rst.roles import code_role
 from docutils.parsers.rst.states import Inliner
 from docutils.statemachine import StringList
+from myst_parser.mocking import MockInliner
 from sphinx import addnodes
 from sphinx.application import Sphinx
 from sphinx.directives.code import CodeBlock
@@ -101,21 +102,31 @@ def __call__(  # pylint: disable=dangerous-default-value
         rawtext: str,
         text: str,
         lineno: int,
-        inliner: Inliner,
+        inliner: Inliner | MockInliner,
         # We allow mutable defaults as the Sphinx implementation requires it.
         options: dict[Any, Any] = {},  # noqa: B006
         content: list[str] = [],  # noqa: B006
     ) -> tuple[list[Node], list[system_message]]:
         """
         Replace placeholders with given variables.
         """
-        inliner_document = inliner.document
-        for name, value in inliner_document.substitution_defs.items():
+        for name, value in inliner.document.substitution_defs.items():
             replacement = value.astext()
             text = text.replace(f"|{name}|", replacement)
             rawtext = text.replace(f"|{name}|", replacement)
             rawtext = rawtext.replace(name, replacement)
 
+        # ``types-docutils`` says that ``code_role`` requires an ``Inliner``
+        # for ``inliner``.
+        #
+        # We can remove this when
+        # https://github.com/executablebooks/MyST-Parser/issues/1017
+        # is resolved by typing ``inliner`` as ``Inliner``.
+        if isinstance(inliner, MockInliner):
+            new_inliner = Inliner()
+            new_inliner.document = inliner.document
+            inliner = new_inliner
+
         return code_role(
             role=typ,
             rawtext=rawtext,