Raise error if ImageGrab subprocess gives non-zero returncode

Tests/test_imagegrab.py

@@ -9,7 +9,7 @@
 
 from PIL import Image, ImageGrab
 
-from .helper import assert_image_equal_tofile, skip_unless_feature
+from .helper import assert_image_equal_tofile, on_ci, skip_unless_feature
 
 
 class TestImageGrab:
@@ -60,12 +60,44 @@ def test_grab_invalid_xdisplay(self) -> None:
             ImageGrab.grab(xdisplay="error.test:0.0")
         assert str(e.value).startswith("X connection failed")
 
-    @pytest.mark.skipif(sys.platform != "win32", reason="Windows only")
+    @pytest.mark.skipif(
+        sys.platform != "darwin" or not on_ci(), reason="Only runs on macOS CI"
+    )
+    def test_grab_handle(self) -> None:
+        p = subprocess.Popen(
+            [
+                "osascript",
+                "-e",
+                'tell application "Finder"\n'
+                'open ("/" as POSIX file)\n'
+                "get id of front window\n"
+                "end tell",
+            ],
+            stdout=subprocess.PIPE,
+        )
+        stdout = p.stdout
+        assert stdout is not None
+        window = int(stdout.read())
+
+        ImageGrab.grab(window=window)
+
+        im = ImageGrab.grab((0, 0, 10, 10), window=window)
+        assert im.size == (10, 10)
+
+    @pytest.mark.skipif(
+        sys.platform not in ("darwin", "win32"), reason="macOS and Windows only"
+    )
     def test_grab_invalid_handle(self) -> None:
-        with pytest.raises(OSError, match="unable to get device context for handle"):
-            ImageGrab.grab(window=-1)
-        with pytest.raises(OSError, match="screen grab failed"):
-            ImageGrab.grab(window=0)
+        if sys.platform == "darwin":
+            with pytest.raises(subprocess.CalledProcessError):
+                ImageGrab.grab(window=-1)
+        else:
+            with pytest.raises(
+                OSError, match="unable to get device context for handle"
+            ):
+                ImageGrab.grab(window=-1)
+            with pytest.raises(OSError, match="screen grab failed"):
+                ImageGrab.grab(window=0)
 
     def test_grabclipboard(self) -> None:
         if sys.platform == "darwin":

src/PIL/ImageGrab.py

@@ -43,25 +43,29 @@ def grab(
             fh, filepath = tempfile.mkstemp(".png")
             os.close(fh)
             args = ["screencapture"]
-            if window:
+            if window is not None:
                 args += ["-l", str(window)]
             elif bbox:
                 left, top, right, bottom = bbox
                 args += ["-R", f"{left},{top},{right-left},{bottom-top}"]
-            subprocess.call(args + ["-x", filepath])
+            args += ["-x", filepath]
+            retcode = subprocess.call(args)
+            if retcode:
+                raise subprocess.CalledProcessError(retcode, args)
             im = Image.open(filepath)
             im.load()
             os.unlink(filepath)
             if bbox:
-                if window:
+                if window is not None:
                     # Determine if the window was in Retina mode or not
                     # by capturing it without the shadow,
                     # and checking how different the width is
                     fh, filepath = tempfile.mkstemp(".png")
                     os.close(fh)
-                    subprocess.call(
-                        ["screencapture", "-l", str(window), "-o", "-x", filepath]
-                    )
+                    args = ["screencapture", "-l", str(window), "-o", "-x", filepath]
+                    retcode = subprocess.call(args)
+                    if retcode:
+                        raise subprocess.CalledProcessError(retcode, args)
                     with Image.open(filepath) as im_no_shadow:
                         retina = im.width - im_no_shadow.width > 100
                     os.unlink(filepath)
@@ -125,7 +129,10 @@ def grab(
                 raise
             fh, filepath = tempfile.mkstemp(".png")
             os.close(fh)
-            subprocess.call(args + [filepath])
+            args.append(filepath)
+            retcode = subprocess.call(args)
+            if retcode:
+                raise subprocess.CalledProcessError(retcode, args)
             im = Image.open(filepath)
             im.load()
             os.unlink(filepath)