Enable Mypy strict mode

.ci/requirements-mypy.txt

@@ -4,7 +4,8 @@ arro3-core
 IceSpringPySideStubs-PyQt6
 IceSpringPySideStubs-PySide6
 ipython
-numpy==2.4.6
+numpy==2.4.6;python_version=="3.11"
+numpy;python_version>="3.12"
 packaging
 pyarrow-stubs
 pybind11

.github/workflows/lint.yml

@@ -28,5 +28,23 @@ jobs:
         uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
       - name: Lint
         run: uvx --with tox-uv tox -e lint
+  mypy:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [
+          "3.14",
+          "3.13",
+          "3.12",
+          "3.11",
+        ]
+    name: Mypy
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Install uv
+        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
       - name: Mypy
-        run: uvx --with tox-uv tox -e mypy
+        run: uvx --python=${{ matrix.python-version }} --with tox-uv tox -e mypy

Tests/conftest.py

@@ -10,7 +10,7 @@
 
 gil_enabled_at_start = True
 if FREE_THREADED_BUILD:
-    gil_enabled_at_start = sys._is_gil_enabled()  # type: ignore[attr-defined]
+    gil_enabled_at_start = sys._is_gil_enabled()  # type: ignore[attr-defined,unused-ignore]
 
 
 def pytest_report_header(config: pytest.Config) -> str:
@@ -28,7 +28,7 @@ def pytest_terminal_summary(terminalreporter: pytest.TerminalReporter) -> None:
     if (
         FREE_THREADED_BUILD
         and not gil_enabled_at_start
-        and sys._is_gil_enabled()  # type: ignore[attr-defined]
+        and sys._is_gil_enabled()  # type: ignore[attr-defined,unused-ignore]
     ):
         tr = terminalreporter
         tr.ensure_newline()

pyproject.toml

@@ -192,16 +192,14 @@ exclude = [
   "^Tests/images/picins/",
   "^Tests/images/sunraster/",
 ]
-follow_imports = "silent"
-python_version = "3.11"
-disallow_any_generics = true
-disallow_untyped_defs = true
-warn_redundant_casts = true
-warn_unused_ignores = true
+disallow_subclassing_any = false
+disallow_untyped_calls = false
+warn_return_any = false
 warn_unreachable = true
 enable_error_code = "ignore-without-code"
-extra_checks = true
+strict = true
 pretty = true
+no_implicit_reexport = false
 num_workers = 4
 
 [tool.pytest]

src/PIL/EpsImagePlugin.py

@@ -203,7 +203,9 @@ def _open(self) -> None:
         imagedata_size: tuple[int, int] | None = None
 
         byte_arr = bytearray(255)
-        bytes_mv = memoryview(byte_arr)
+        # the extra `bytes` annotation here works around several false positive
+        # `comparison-overlap` mypy errors
+        bytes_mv: bytes | memoryview = memoryview(byte_arr)
         bytes_read = 0
         reading_header_comments = True
         reading_trailer_comments = False

src/PIL/GifImagePlugin.py

@@ -1195,8 +1195,9 @@ class Collector(BytesIO):
         data = []
 
         def write(self, data: Buffer) -> int:
-            self.data.append(data)
-            return len(data)
+            data_bytes = bytes(data)
+            self.data.append(data_bytes)
+            return len(data_bytes)
 
     im.load()  # make sure raster data is available
 

src/PIL/ImageGrab.py

@@ -79,7 +79,7 @@ def grab(
                         scale = 1 if scale_down else 2
                         im_cropped = im.resize(
                             ((right - left) * scale, (bottom - top) * scale),
-                            box=tuple(coord * 2 for coord in bbox),
+                            box=(left * 2, top * 2, right * 2, bottom * 2),
                         )
                     else:
                         im_cropped = im.crop(bbox)