Mark StubHandler.open() as abstract

Tests/test_file_bufrstub.py

@@ -20,7 +20,7 @@ def test_open() -> None:
 
         # Dummy data from the stub
         assert im.mode == "F"
-        assert im.size == (1, 1)
+        assert im.size == (0, 0)
 
 
 def test_invalid_file() -> None:
@@ -58,6 +58,7 @@ class TestHandler(ImageFile.StubHandler):
 
         def open(self, im: ImageFile.StubImageFile) -> None:
             self.opened = True
+            im._size = (1, 1)
 
         def load(self, im: ImageFile.StubImageFile) -> Image.Image:
             self.loaded = True

Tests/test_file_gribstub.py

@@ -20,7 +20,7 @@ def test_open() -> None:
 
         # Dummy data from the stub
         assert im.mode == "F"
-        assert im.size == (1, 1)
+        assert im.size == (0, 0)
 
 
 def test_invalid_file() -> None:
@@ -58,6 +58,7 @@ class TestHandler(ImageFile.StubHandler):
 
         def open(self, im: Image.Image) -> None:
             self.opened = True
+            im._size = (1, 1)
 
         def load(self, im: ImageFile.ImageFile) -> Image.Image:
             self.loaded = True

Tests/test_file_hdf5stub.py

@@ -19,7 +19,7 @@ def test_open() -> None:
 
         # Dummy data from the stub
         assert im.mode == "F"
-        assert im.size == (1, 1)
+        assert im.size == (0, 0)
 
 
 def test_invalid_file() -> None:
@@ -60,6 +60,7 @@ class TestHandler(ImageFile.StubHandler):
 
         def open(self, im: Image.Image) -> None:
             self.opened = True
+            im._size = (1, 1)
 
         def load(self, im: ImageFile.ImageFile) -> Image.Image:
             self.loaded = True

Tests/test_file_wmf.py

@@ -69,14 +69,17 @@ def test_register_handler(tmp_path: Path) -> None:
     class TestHandler(ImageFile.StubHandler):
         methodCalled = False
 
+        def open(self, im: ImageFile.StubImageFile) -> None:
+            im._size = (1, 1)
+
         def load(self, im: ImageFile.StubImageFile) -> Image.Image:
             return Image.new("RGB", (1, 1))
 
         def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
             self.methodCalled = True
 
     handler = TestHandler()
-    original_handler = WmfImagePlugin._handler
+    original_handler = WmfImagePlugin.WmfStubImageFile._handler
     WmfImagePlugin.register_handler(handler)
 
     im = hopper()

src/PIL/BufrStubImagePlugin.py

@@ -15,17 +15,14 @@
 
 from . import Image, ImageFile
 
-_handler = None
-
 
 def register_handler(handler: ImageFile.StubHandler | None) -> None:
     """
     Install application-specific BUFR image handler.
 
     :param handler: Handler object.
     """
-    global _handler
-    _handler = handler
+    BufrStubImageFile._handler = handler
 
 
 # --------------------------------------------------------------------
@@ -50,17 +47,15 @@ def _open(self) -> None:
 
         # make something up
         self._mode = "F"
-        self._size = 1, 1
-
-    def _load(self) -> ImageFile.StubHandler | None:
-        return _handler
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    if _handler is None or not hasattr(_handler, "save"):
+    if BufrStubImageFile._handler is None or not hasattr(
+        BufrStubImageFile._handler, "save"
+    ):
         msg = "BUFR save handler not installed"
         raise OSError(msg)
-    _handler.save(im, fp, filename)
+    BufrStubImageFile._handler.save(im, fp, filename)
 
 
 # --------------------------------------------------------------------

src/PIL/GribStubImagePlugin.py

@@ -15,17 +15,14 @@
 
 from . import Image, ImageFile
 
-_handler = None
-
 
 def register_handler(handler: ImageFile.StubHandler | None) -> None:
     """
     Install application-specific GRIB image handler.
 
     :param handler: Handler object.
     """
-    global _handler
-    _handler = handler
+    GribStubImageFile._handler = handler
 
 
 # --------------------------------------------------------------------
@@ -50,17 +47,15 @@ def _open(self) -> None:
 
         # make something up
         self._mode = "F"
-        self._size = 1, 1
-
-    def _load(self) -> ImageFile.StubHandler | None:
-        return _handler
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    if _handler is None or not hasattr(_handler, "save"):
+    if GribStubImageFile._handler is None or not hasattr(
+        GribStubImageFile._handler, "save"
+    ):
         msg = "GRIB save handler not installed"
         raise OSError(msg)
-    _handler.save(im, fp, filename)
+    GribStubImageFile._handler.save(im, fp, filename)
 
 
 # --------------------------------------------------------------------

src/PIL/Hdf5StubImagePlugin.py

@@ -15,17 +15,14 @@
 
 from . import Image, ImageFile
 
-_handler = None
-
 
 def register_handler(handler: ImageFile.StubHandler | None) -> None:
     """
     Install application-specific HDF5 image handler.
 
     :param handler: Handler object.
     """
-    global _handler
-    _handler = handler
+    HDF5StubImageFile._handler = handler
 
 
 # --------------------------------------------------------------------
@@ -50,17 +47,15 @@ def _open(self) -> None:
 
         # make something up
         self._mode = "F"
-        self._size = 1, 1
-
-    def _load(self) -> ImageFile.StubHandler | None:
-        return _handler
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    if _handler is None or not hasattr(_handler, "save"):
+    if HDF5StubImageFile._handler is None or not hasattr(
+        HDF5StubImageFile._handler, "save"
+    ):
         msg = "HDF5 save handler not installed"
         raise OSError(msg)
-    _handler.save(im, fp, filename)
+    HDF5StubImageFile._handler.save(im, fp, filename)
 
 
 # --------------------------------------------------------------------

src/PIL/ImageFile.py

@@ -151,9 +151,8 @@ def __init__(
             try:
                 self._open()
 
-                if isinstance(self, StubImageFile):
-                    if loader := self._load():
-                        loader.open(self)
+                if isinstance(self, StubImageFile) and self._handler:
+                    self._handler.open(self)
             except (
                 IndexError,  # end of data
                 TypeError,  # end of data (ord)
@@ -163,7 +162,11 @@ def __init__(
             ) as v:
                 raise SyntaxError(v) from v
 
-            if not self.mode or self.size[0] <= 0 or self.size[1] <= 0:
+            if not self.mode or (
+                min(self.size) < 0
+                if isinstance(self, StubImageFile) and self._handler is None
+                else min(self.size) <= 0
+            ):
                 msg = "not identified by this driver"
                 raise SyntaxError(msg)
         except BaseException:
@@ -468,6 +471,7 @@ def _seek_check(self, frame: int) -> bool:
 
 
 class StubHandler(abc.ABC):
+    @abc.abstractmethod
     def open(self, im: StubImageFile) -> None:
         pass
 
@@ -484,27 +488,23 @@ class StubImageFile(ImageFile, metaclass=abc.ABCMeta):
     certain format, but relies on external code to load the file.
     """
 
+    _handler: StubHandler | None = None
+
     @abc.abstractmethod
     def _open(self) -> None:
         pass
 
     def load(self) -> Image.core.PixelAccess | None:
-        loader = self._load()
-        if loader is None:
+        if self._handler is None:
             msg = f"cannot find loader for this {self.format} file"
             raise OSError(msg)
-        image = loader.load(self)
+        image = self._handler.load(self)
         assert image is not None
         # become the other object (!)
         self.__class__ = image.__class__  # type: ignore[assignment]
         self.__dict__ = image.__dict__
         return image.load()
 
-    @abc.abstractmethod
-    def _load(self) -> StubHandler | None:
-        """(Hook) Find actual image loader."""
-        pass
-
 
 class Parser:
     """

src/PIL/WmfImagePlugin.py

@@ -27,41 +27,6 @@
 from ._binary import si16le as short
 from ._binary import si32le as _long
 
-_handler = None
-
-
-def register_handler(handler: ImageFile.StubHandler | None) -> None:
-    """
-    Install application-specific WMF image handler.
-
-    :param handler: Handler object.
-    """
-    global _handler
-    _handler = handler
-
-
-if hasattr(Image.core, "drawwmf"):
-    # install default handler (windows only)
-
-    class WmfHandler(ImageFile.StubHandler):
-        def open(self, im: ImageFile.StubImageFile) -> None:
-            self.bbox = im.info["wmf_bbox"]
-
-        def load(self, im: ImageFile.StubImageFile) -> Image.Image:
-            assert im.fp is not None
-            im.fp.seek(0)  # rewind
-            return Image.frombytes(
-                "RGB",
-                im.size,
-                Image.core.drawwmf(im.fp.read(), im.size, self.bbox),
-                "raw",
-                "BGR",
-                (im.size[0] * 3 + 3) & -4,
-                -1,
-            )
-
-    register_handler(WmfHandler())
-
 #
 # --------------------------------------------------------------------
 # Read WMF file
@@ -147,9 +112,6 @@ def _open(self) -> None:
         self._mode = "RGB"
         self._size = size
 
-    def _load(self) -> ImageFile.StubHandler | None:
-        return _handler
-
     def load(
         self, dpi: float | tuple[float, float] | None = None
     ) -> Image.core.PixelAccess | None:
@@ -166,10 +128,44 @@ def load(
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    if _handler is None or not hasattr(_handler, "save"):
+    if WmfStubImageFile._handler is None or not hasattr(
+        WmfStubImageFile._handler, "save"
+    ):
         msg = "WMF save handler not installed"
         raise OSError(msg)
-    _handler.save(im, fp, filename)
+    WmfStubImageFile._handler.save(im, fp, filename)
+
+
+def register_handler(handler: ImageFile.StubHandler | None) -> None:
+    """
+    Install application-specific WMF image handler.
+
+    :param handler: Handler object.
+    """
+    WmfStubImageFile._handler = handler
+
+
+if hasattr(Image.core, "drawwmf"):
+    # install default handler (windows only)
+
+    class WmfHandler(ImageFile.StubHandler):
+        def open(self, im: ImageFile.StubImageFile) -> None:
+            self.bbox = im.info["wmf_bbox"]
+
+        def load(self, im: ImageFile.StubImageFile) -> Image.Image:
+            assert im.fp is not None
+            im.fp.seek(0)  # rewind
+            return Image.frombytes(
+                "RGB",
+                im.size,
+                Image.core.drawwmf(im.fp.read(), im.size, self.bbox),
+                "raw",
+                "BGR",
+                (im.size[0] * 3 + 3) & -4,
+                -1,
+            )
+
+    register_handler(WmfHandler())
 
 
 #