Ship py.typed and type-check with mypy

.github/workflows/pythonapp.yml

@@ -22,6 +22,7 @@ jobs:
       env:
         GH_TOKEN: ${{ github.token }}  # enables online audits (known-vulnerable-actions, impostor-commit)
       run: uv run zizmor --format=github .
+    - run: uv run mypy
 
   test:
     runs-on: ubuntu-latest

CLAUDE.md

@@ -10,6 +10,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 - Lowest supported Markdown: `uv run --isolated --python 3.10 --with "markdown==3.2.*" pytest`
 - Lint/format (CI fails on either): `uv run ruff check .` and `uv run ruff format --check .`
 - Workflow audit (also in CI): `GH_TOKEN=$(gh auth token) uv run zizmor .`. Config in `.github/zizmor.yml` (its Dependabot cooldown must match `.github/dependabot.yml`).
+- Type check (also in CI): `uv run mypy` (strict, covers `md_condition` and `tests`). The package ships `py.typed`.
 - Build: `uv build`. The version comes from the latest git tag via setuptools-scm; there is no version field to edit.
 
 ## Code

md_condition/__init__.py

@@ -1,8 +1,10 @@
+from typing import Any
+
 from md_condition.extension import ConditionExtension
 from md_condition.preprocessor import ConditionSyntaxError
 
 __all__ = ["ConditionExtension", "ConditionSyntaxError", "makeExtension"]
 
 
-def makeExtension(**kwargs) -> ConditionExtension:
+def makeExtension(**kwargs: Any) -> ConditionExtension:
     return ConditionExtension(**kwargs)

md_condition/extension.py

@@ -1,11 +1,13 @@
+from typing import Any
+
 from markdown import Markdown
 from markdown.extensions import Extension
 
 from md_condition.preprocessor import ConditionPreprocessor
 
 
 class ConditionExtension(Extension):
-    def __init__(self, **kwargs) -> None:
+    def __init__(self, **kwargs: Any) -> None:
         self.config = {
             "symbol": ["", "Defined symbol(s): a string separated by spaces/`|`, or a list"],
         }

md_condition/preprocessor.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import re
+from collections.abc import Iterable
 from typing import TYPE_CHECKING
 
 from markdown import Markdown
@@ -42,6 +43,7 @@ def __init__(self, md: Markdown, extension: ConditionExtension) -> None:
         # `symbol` is a string ("DEBUG", "DEBUG RELEASE", "DEBUG|RELEASE"), a list of them,
         # or a YAML scalar such as 2024 (stringified)
         symbol = extension.getConfig("symbol")
+        values: Iterable[object]
         if symbol is None:
             values = []
         elif isinstance(symbol, (list, tuple, set, frozenset)):
@@ -161,8 +163,7 @@ def _error(number: int, line: str, message: str) -> ConditionSyntaxError:
     def _closes_fence(cls, line: str, fence: str) -> bool:
         # CommonMark: same character, at least as long, nothing else on the line
         closing = cls.RE_FENCE_CLOSE.match(line)
-        return (
-            bool(closing)
-            and closing.group(1)[0] == fence[0]
-            and len(closing.group(1)) >= len(fence)
-        )
+        if closing is None:
+            return False
+        marker = closing.group(1)
+        return marker[0] == fence[0] and len(marker) >= len(fence)

pyproject.toml

@@ -15,6 +15,7 @@ dependencies = ["Markdown>=3.2"]
 classifiers = [
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3 :: Only",
+    "Typing :: Typed",
     "Topic :: Text Processing :: Markup :: Markdown",
 ]
 
@@ -23,8 +24,10 @@ Homepage = "https://github.com/cssho/md-condition"
 
 [dependency-groups]
 dev = [
+    "mypy>=2.4.0",
     "pytest>=8",
     "ruff>=0.14",
+    "types-markdown>=3.10.2.20261007",
     "zizmor>=1.30.1",
 ]
 
@@ -42,3 +45,7 @@ select = ["E", "F", "W", "I", "UP", "B"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
+
+[tool.mypy]
+strict = true
+files = ["md_condition", "tests"]

tests/test_condition.py

@@ -140,7 +140,7 @@ def test_symbol_is_matched_as_whole_name(symbol: str, condition: str, kept: bool
         pytest.param(None, False, False, id="none"),
     ],
 )
-def test_multiple_symbols(symbol, debug: bool, release: bool) -> None:
+def test_multiple_symbols(symbol: object, debug: bool, release: bool) -> None:
     md = markdown.Markdown(extensions=[ConditionExtension(symbol=symbol)])
     expected = "<h1>1</h1>\n<p>{}</p>\n<h1>2</h1>\n<p>{}</p>".format(
         "DEBUG" if debug else "No DEBUG", "RELEASE" if release else "No RELEASE"

tests/test_fences.py

@@ -8,7 +8,7 @@
 from md_condition import ConditionExtension, ConditionSyntaxError
 
 
-def preprocess(source: str, symbol="DEBUG") -> str:
+def preprocess(source: str, symbol: object = "DEBUG") -> str:
     md = markdown.Markdown(extensions=[ConditionExtension(symbol=symbol)])
     lines = textwrap.dedent(source).split("\n")
     return "\n".join(md.preprocessors["condition"].run(lines))
@@ -152,7 +152,7 @@ def test_error_message_includes_the_line() -> None:
         pytest.param([2024, "DEBUG"], "2024", id="int_in_list"),
     ],
 )
-def test_yaml_scalar_symbols(symbol, condition: str) -> None:
+def test_yaml_scalar_symbols(symbol: object, condition: str) -> None:
     # YAML turns `symbol: 2024` / `symbol: yes` into int / bool
     assert preprocess(f"<!--- #if {condition} -->\nyes\n<!--- #endif -->", symbol=symbol) == "yes"