Add ImageFile context manager (#9367)

Author: hugovk

Tests/test_file_jpeg2k.py

@@ -164,7 +164,7 @@ def test_reduce() -> None:
     with Image.open("Tests/images/test-card-lossless.jp2") as im:
         assert callable(im.reduce)
 
-        im.reduce = 2
+        im.reduce = 2  # type: ignore[assignment, method-assign]
         assert im.reduce == 2
 
         im.load()

Tests/test_file_png.py

@@ -823,7 +823,7 @@ class MyStdOut:
         monkeypatch.setattr(sys, "stdout", mystdout)
 
         with Image.open(TEST_PNG_FILE) as im:
-            im.save(sys.stdout, "PNG")
+            im.save(sys.stdout, "PNG")  # type: ignore[arg-type]
 
         if isinstance(mystdout, MyStdOut):
             mystdout = mystdout.buffer

Tests/test_file_ppm.py

@@ -389,7 +389,7 @@ class MyStdOut:
     monkeypatch.setattr(sys, "stdout", mystdout)
 
     with Image.open(TEST_FILE) as im:
-        im.save(sys.stdout, "PPM")
+        im.save(sys.stdout, "PPM")  # type: ignore[arg-type]
 
     if isinstance(mystdout, MyStdOut):
         mystdout = mystdout.buffer

Tests/test_image_transform.py

@@ -250,14 +250,14 @@ def test_blank_fill(self) -> None:
     def test_missing_method_data(self) -> None:
         with hopper() as im:
             with pytest.raises(ValueError):
-                im.transform((100, 100), None)
+                im.transform((100, 100), None)  # type: ignore[arg-type]
 
     @pytest.mark.parametrize("resample", (Image.Resampling.BOX, "unknown"))
     def test_unknown_resampling_filter(self, resample: Image.Resampling | str) -> None:
         with hopper() as im:
             (w, h) = im.size
             with pytest.raises(ValueError):
-                im.transform((100, 100), Image.Transform.EXTENT, (0, 0, w, h), resample)
+                im.transform((100, 100), Image.Transform.EXTENT, (0, 0, w, h), resample)  # type: ignore[arg-type]
 
 
 class TestImageTransformAffine:

src/PIL/Image.py

@@ -590,16 +590,11 @@ def _new(self, im: core.ImagingCore) -> Image:
         return new
 
     # Context manager support
-    def __enter__(self):
+    def __enter__(self) -> Image:
         return self
 
-    def __exit__(self, *args):
-        from . import ImageFile
-
-        if isinstance(self, ImageFile.ImageFile):
-            if getattr(self, "_exclusive_fp", False):
-                self._close_fp()
-            self.fp = None
+    def __exit__(self, *args: object) -> None:
+        pass
 
     def close(self) -> None:
         """

src/PIL/ImageFile.py

@@ -131,6 +131,7 @@ def __init__(
         self.decoderconfig: tuple[Any, ...] = ()
         self.decodermaxblock = MAXBLOCK
 
+        self.fp: IO[bytes] | None
         self._fp: IO[bytes] | DeferredError
         if is_path(fp):
             # filename
@@ -168,6 +169,10 @@ def __init__(
     def _open(self) -> None:
         pass
 
+    # Context manager support
+    def __enter__(self) -> ImageFile:
+        return self
+
     def _close_fp(self) -> None:
         if getattr(self, "_fp", False) and not isinstance(self._fp, DeferredError):
             if self._fp != self.fp:
@@ -176,6 +181,11 @@ def _close_fp(self) -> None:
         if self.fp:
             self.fp.close()
 
+    def __exit__(self, *args: object) -> None:
+        if getattr(self, "_exclusive_fp", False):
+            self._close_fp()
+        self.fp = None
+
     def close(self) -> None:
         """
         Closes the file pointer, if possible.
@@ -268,7 +278,7 @@ def verify(self) -> None:
 
         # raise exception if something's wrong.  must be called
         # directly after open, and closes file when finished.
-        if self._exclusive_fp:
+        if self._exclusive_fp and self.fp:
             self.fp.close()
         self.fp = None