Add type hints to _convert and lowlevel; add type-checking infrastructure

.pre-commit-config.yaml

@@ -53,6 +53,14 @@ repos:
         name: Lint python code with flake8
         additional_dependencies: [flake8-bugbear, Flake8-pyproject]
 
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.11.2
+    hooks:
+      - id: mypy
+        name: Check Python types
+        additional_dependencies: [openslide-bin, pillow, types-setuptools]
+        exclude: "^(doc/.*|openslide/(__init__|deepzoom)\\.py|tests/.*|examples/deepzoom/.*)$"
+
   - repo: https://github.com/rstcheck/rstcheck
     rev: v6.2.4
     hooks:

openslide/__init__.py

@@ -32,13 +32,17 @@
 
 from openslide import lowlevel
 
-# For the benefit of library users
-from openslide._version import __version__  # noqa: F401  module-imported-but-unused
+# Re-exports for the benefit of library users
+from openslide._version import (  # noqa: F401  module-imported-but-unused
+    __version__ as __version__,
+)
+from openslide.lowlevel import (
+    OpenSlideUnsupportedFormatError as OpenSlideUnsupportedFormatError,
+)
 from openslide.lowlevel import (  # noqa: F401  module-imported-but-unused
-    OpenSlideError,
-    OpenSlideUnsupportedFormatError,
-    OpenSlideVersionError,
+    OpenSlideVersionError as OpenSlideVersionError,
 )
+from openslide.lowlevel import OpenSlideError as OpenSlideError
 
 __library_version__ = lowlevel.get_version()
 

openslide/_convert.pyi

@@ -0,0 +1,26 @@
+#
+# openslide-python - Python bindings for the OpenSlide library
+#
+# Copyright (c) 2024 Benjamin Gilbert
+#
+# This library is free software; you can redistribute it and/or modify it
+# under the terms of version 2.1 of the GNU Lesser General Public License
+# as published by the Free Software Foundation.
+#
+# This library is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+# License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+
+from typing import Protocol
+
+class _Buffer(Protocol):
+    # Python 3.12+ has collections.abc.Buffer
+    def __buffer__(self, flags: int) -> memoryview: ...
+
+def argb2rgba(buf: _Buffer) -> None: ...