Improve handling of file resources (#3577)

Improve handling of file resources

Tests/test_bmp_reference.py

@@ -24,8 +24,8 @@ def test_bad(self):
 
             def open(f):
                 try:
-                    im = Image.open(f)
-                    im.load()
+                    with Image.open(f) as im:
+                        im.load()
                 except Exception:  # as msg:
                     pass
 
@@ -48,8 +48,8 @@ def test_questionable(self):
         ]
         for f in self.get_files("q"):
             try:
-                im = Image.open(f)
-                im.load()
+                with Image.open(f) as im:
+                    im.load()
                 if os.path.basename(f) not in supported:
                     print("Please add %s to the partially supported bmp specs." % f)
             except Exception:  # as msg:
@@ -89,17 +89,17 @@ def get_compare(f):
 
         for f in self.get_files("g"):
             try:
-                im = Image.open(f)
-                im.load()
-                compare = Image.open(get_compare(f))
-                compare.load()
-                if im.mode == "P":
-                    # assert image similar doesn't really work
-                    # with paletized image, since the palette might
-                    # be differently ordered for an equivalent image.
-                    im = im.convert("RGBA")
-                    compare = im.convert("RGBA")
-                self.assert_image_similar(im, compare, 5)
+                with Image.open(f) as im:
+                    im.load()
+                    with Image.open(get_compare(f)) as compare:
+                        compare.load()
+                        if im.mode == "P":
+                            # assert image similar doesn't really work
+                            # with paletized image, since the palette might
+                            # be differently ordered for an equivalent image.
+                            im = im.convert("RGBA")
+                            compare = im.convert("RGBA")
+                        self.assert_image_similar(im, compare, 5)
 
             except Exception as msg:
                 # there are three here that are unsupported:

Tests/test_decompression_bomb.py

@@ -14,7 +14,8 @@ def tearDown(self):
     def test_no_warning_small_file(self):
         # Implicit assert: no warning.
         # A warning would cause a failure.
-        Image.open(TEST_FILE)
+        with Image.open(TEST_FILE):
+            pass
 
     def test_no_warning_no_limit(self):
         # Arrange
@@ -25,21 +26,28 @@ def test_no_warning_no_limit(self):
         # Act / Assert
         # Implicit assert: no warning.
         # A warning would cause a failure.
-        Image.open(TEST_FILE)
+        with Image.open(TEST_FILE):
+            pass
 
     def test_warning(self):
         # Set limit to trigger warning on the test file
         Image.MAX_IMAGE_PIXELS = 128 * 128 - 1
         self.assertEqual(Image.MAX_IMAGE_PIXELS, 128 * 128 - 1)
 
-        self.assert_warning(Image.DecompressionBombWarning, Image.open, TEST_FILE)
+        def open():
+            with Image.open(TEST_FILE):
+                pass
+
+        self.assert_warning(Image.DecompressionBombWarning, open)
 
     def test_exception(self):
         # Set limit to trigger exception on the test file
         Image.MAX_IMAGE_PIXELS = 64 * 128 - 1
         self.assertEqual(Image.MAX_IMAGE_PIXELS, 64 * 128 - 1)
 
-        self.assertRaises(Image.DecompressionBombError, lambda: Image.open(TEST_FILE))
+        with self.assertRaises(Image.DecompressionBombError):
+            with Image.open(TEST_FILE):
+                pass
 
     def test_exception_ico(self):
         with self.assertRaises(Image.DecompressionBombError):
@@ -53,6 +61,7 @@ def test_exception_gif(self):
 class TestDecompressionCrop(PillowTestCase):
     def setUp(self):
         self.src = hopper()
+        self.addCleanup(self.src.close)
         Image.MAX_IMAGE_PIXELS = self.src.height * self.src.width * 4 - 1
 
     def tearDown(self):

Tests/test_file_blp.py

@@ -5,14 +5,14 @@
 
 class TestFileBlp(PillowTestCase):
     def test_load_blp2_raw(self):
-        im = Image.open("Tests/images/blp/blp2_raw.blp")
-        target = Image.open("Tests/images/blp/blp2_raw.png")
-        self.assert_image_equal(im, target)
+        with Image.open("Tests/images/blp/blp2_raw.blp") as im:
+            with Image.open("Tests/images/blp/blp2_raw.png") as target:
+                self.assert_image_equal(im, target)
 
     def test_load_blp2_dxt1(self):
-        im = Image.open("Tests/images/blp/blp2_dxt1.blp")
-        target = Image.open("Tests/images/blp/blp2_dxt1.png")
-        self.assert_image_equal(im, target)
+        with Image.open("Tests/images/blp/blp2_dxt1.blp") as im:
+            with Image.open("Tests/images/blp/blp2_dxt1.png") as target:
+                self.assert_image_equal(im, target)
 
     def test_load_blp2_dxt1a(self):
         im = Image.open("Tests/images/blp/blp2_dxt1a.blp")

Tests/test_file_bmp.py

@@ -46,13 +46,12 @@ def test_dpi(self):
         dpi = (72, 72)
 
         output = io.BytesIO()
-        im = hopper()
-        im.save(output, "BMP", dpi=dpi)
+        with hopper() as im:
+            im.save(output, "BMP", dpi=dpi)
 
         output.seek(0)
-        reloaded = Image.open(output)
-
-        self.assertEqual(reloaded.info["dpi"], dpi)
+        with Image.open(output) as reloaded:
+            self.assertEqual(reloaded.info["dpi"], dpi)
 
     def test_save_bmp_with_dpi(self):
         # Test for #1301
@@ -72,24 +71,24 @@ def test_save_bmp_with_dpi(self):
 
     def test_load_dpi_rounding(self):
         # Round up
-        im = Image.open("Tests/images/hopper.bmp")
-        self.assertEqual(im.info["dpi"], (96, 96))
+        with Image.open("Tests/images/hopper.bmp") as im:
+            self.assertEqual(im.info["dpi"], (96, 96))
 
         # Round down
-        im = Image.open("Tests/images/hopper_roundDown.bmp")
-        self.assertEqual(im.info["dpi"], (72, 72))
+        with Image.open("Tests/images/hopper_roundDown.bmp") as im:
+            self.assertEqual(im.info["dpi"], (72, 72))
 
     def test_save_dpi_rounding(self):
         outfile = self.tempfile("temp.bmp")
         im = Image.open("Tests/images/hopper.bmp")
 
         im.save(outfile, dpi=(72.2, 72.2))
-        reloaded = Image.open(outfile)
-        self.assertEqual(reloaded.info["dpi"], (72, 72))
+        with Image.open(outfile) as reloaded:
+            self.assertEqual(reloaded.info["dpi"], (72, 72))
 
-        im.save(outfile, dpi=(72.8, 72.8))
-        reloaded = Image.open(outfile)
-        self.assertEqual(reloaded.info["dpi"], (73, 73))
+            im.save(outfile, dpi=(72.8, 72.8))
+        with Image.open(outfile) as reloaded:
+            self.assertEqual(reloaded.info["dpi"], (73, 73))
 
     def test_load_dib(self):
         # test for #1293, Imagegrab returning Unsupported Bitfields Format

Tests/test_file_bufrstub.py

@@ -8,14 +8,14 @@
 class TestFileBufrStub(PillowTestCase):
     def test_open(self):
         # Act
-        im = Image.open(TEST_FILE)
+        with Image.open(TEST_FILE) as im:
 
-        # Assert
-        self.assertEqual(im.format, "BUFR")
+            # Assert
+            self.assertEqual(im.format, "BUFR")
 
-        # Dummy data from the stub
-        self.assertEqual(im.mode, "F")
-        self.assertEqual(im.size, (1, 1))
+            # Dummy data from the stub
+            self.assertEqual(im.mode, "F")
+            self.assertEqual(im.size, (1, 1))
 
     def test_invalid_file(self):
         # Arrange
@@ -28,10 +28,10 @@ def test_invalid_file(self):
 
     def test_load(self):
         # Arrange
-        im = Image.open(TEST_FILE)
+        with Image.open(TEST_FILE) as im:
 
-        # Act / Assert: stub cannot load without an implemented handler
-        self.assertRaises(IOError, im.load)
+            # Act / Assert: stub cannot load without an implemented handler
+            self.assertRaises(IOError, im.load)
 
     def test_save(self):
         # Arrange

Tests/test_file_container.py

@@ -11,8 +11,8 @@ def test_sanity(self):
         dir(ContainerIO)
 
     def test_isatty(self):
-        im = hopper()
-        container = ContainerIO.ContainerIO(im, 0, 0)
+        with hopper() as im:
+            container = ContainerIO.ContainerIO(im, 0, 0)
 
         self.assertFalse(container.isatty())
 

Tests/test_file_dcx.py

@@ -1,6 +1,8 @@
+import unittest
+
 from PIL import DcxImagePlugin, Image
 
-from .helper import PillowTestCase, hopper
+from .helper import PillowTestCase, hopper, is_pypy
 
 # Created with ImageMagick: convert hopper.ppm hopper.dcx
 TEST_FILE = "Tests/images/hopper.dcx"
@@ -11,19 +13,35 @@ def test_sanity(self):
         # Arrange
 
         # Act
-        im = Image.open(TEST_FILE)
+        with Image.open(TEST_FILE) as im:
 
-        # Assert
-        self.assertEqual(im.size, (128, 128))
-        self.assertIsInstance(im, DcxImagePlugin.DcxImageFile)
-        orig = hopper()
-        self.assert_image_equal(im, orig)
+            # Assert
+            self.assertEqual(im.size, (128, 128))
+            self.assertIsInstance(im, DcxImagePlugin.DcxImageFile)
+            orig = hopper()
+            self.assert_image_equal(im, orig)
 
+    @unittest.skipIf(is_pypy(), "Requires CPython")
     def test_unclosed_file(self):
         def open():
             im = Image.open(TEST_FILE)
             im.load()
 
+        self.assert_warning(ResourceWarning, open)
+
+    def test_closed_file(self):
+        def open():
+            im = Image.open(TEST_FILE)
+            im.load()
+            im.close()
+
+        self.assert_warning(None, open)
+
+    def test_context_manager(self):
+        def open():
+            with Image.open(TEST_FILE) as im:
+                im.load()
+
         self.assert_warning(None, open)
 
     def test_invalid_file(self):
@@ -32,34 +50,34 @@ def test_invalid_file(self):
 
     def test_tell(self):
         # Arrange
-        im = Image.open(TEST_FILE)
+        with Image.open(TEST_FILE) as im:
 
-        # Act
-        frame = im.tell()
+            # Act
+            frame = im.tell()
 
-        # Assert
-        self.assertEqual(frame, 0)
+            # Assert
+            self.assertEqual(frame, 0)
 
     def test_n_frames(self):
-        im = Image.open(TEST_FILE)
-        self.assertEqual(im.n_frames, 1)
-        self.assertFalse(im.is_animated)
+        with Image.open(TEST_FILE) as im:
+            self.assertEqual(im.n_frames, 1)
+            self.assertFalse(im.is_animated)
 
     def test_eoferror(self):
-        im = Image.open(TEST_FILE)
-        n_frames = im.n_frames
+        with Image.open(TEST_FILE) as im:
+            n_frames = im.n_frames
 
-        # Test seeking past the last frame
-        self.assertRaises(EOFError, im.seek, n_frames)
-        self.assertLess(im.tell(), n_frames)
+            # Test seeking past the last frame
+            self.assertRaises(EOFError, im.seek, n_frames)
+            self.assertLess(im.tell(), n_frames)
 
-        # Test that seeking to the last frame does not raise an error
-        im.seek(n_frames - 1)
+            # Test that seeking to the last frame does not raise an error
+            im.seek(n_frames - 1)
 
     def test_seek_too_far(self):
         # Arrange
-        im = Image.open(TEST_FILE)
-        frame = 999  # too big on purpose
+        with Image.open(TEST_FILE) as im:
+            frame = 999  # too big on purpose
 
         # Act / Assert
         self.assertRaises(EOFError, im.seek, frame)