accept returns bool or str

src/PIL/BlpImagePlugin.py

@@ -241,7 +241,7 @@ class BLPFormatError(NotImplementedError):
     pass
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] in (b"BLP1", b"BLP2")
 
 

src/PIL/BmpImagePlugin.py

@@ -48,7 +48,7 @@
 }
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:2] == b"BM"
 
 

src/PIL/BufrStubImagePlugin.py

@@ -29,7 +29,7 @@ def register_handler(handler):
 # Image adapter
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"BUFR" or prefix[:4] == b"ZCZC"
 
 

src/PIL/CurImagePlugin.py

@@ -25,7 +25,7 @@
 # --------------------------------------------------------------------
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"\0\0\2\0"
 
 

src/PIL/DcxImagePlugin.py

@@ -29,7 +29,7 @@
 MAGIC = 0x3ADE68B1  # QUIZ: what's this value, then?
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return len(prefix) >= 4 and i32(prefix) == MAGIC
 
 

src/PIL/DdsImagePlugin.py

@@ -562,7 +562,7 @@ def _save(im, fp, filename):
     )
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"DDS "
 
 

src/PIL/EpsImagePlugin.py

@@ -195,7 +195,7 @@ def readline(self):
         return b"".join(s).decode("latin-1")
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"%!PS" or (len(prefix) >= 4 and i32(prefix) == 0xC6D3D0C5)
 
 

src/PIL/FliImagePlugin.py

@@ -27,7 +27,7 @@
 # decoder
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return (
         len(prefix) >= 6
         and i16(prefix, 4) in [0xAF11, 0xAF12]

src/PIL/FpxImagePlugin.py

@@ -41,7 +41,7 @@
 # --------------------------------------------------------------------
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:8] == olefile.MAGIC
 
 

src/PIL/FtexImagePlugin.py

@@ -107,7 +107,7 @@ def load_seek(self, pos):
         pass
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == MAGIC
 
 

src/PIL/GbrImagePlugin.py

@@ -29,7 +29,7 @@
 from ._binary import i32be as i32
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return len(prefix) >= 8 and i32(prefix, 0) >= 20 and i32(prefix, 4) in (1, 2)
 
 

src/PIL/GifImagePlugin.py

@@ -60,7 +60,7 @@ class LoadingStrategy(IntEnum):
 # Identify/read GIF files
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:6] in [b"GIF87a", b"GIF89a"]
 
 

src/PIL/GribStubImagePlugin.py

@@ -29,7 +29,7 @@ def register_handler(handler):
 # Image adapter
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"GRIB" and prefix[7] == 1
 
 

src/PIL/Hdf5StubImagePlugin.py

@@ -29,7 +29,7 @@ def register_handler(handler):
 # Image adapter
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:8] == b"\x89HDF\r\n\x1a\n"
 
 

src/PIL/IcnsImagePlugin.py

@@ -374,7 +374,7 @@ def _save(im, fp, filename):
         fp.flush()
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == MAGIC
 
 

src/PIL/IcoImagePlugin.py

@@ -114,7 +114,7 @@ def _save(im, fp, filename):
         fp.seek(current)
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == _MAGIC
 
 

src/PIL/Image.py

@@ -223,7 +223,7 @@ class Quantize(IntEnum):
     str,
     tuple[
         Callable[[IO[bytes], str | bytes], ImageFile.ImageFile],
-        Callable[[bytes], bool] | None,
+        Callable[[bytes], bool | str] | None,
     ],
 ] = {}
 MIME: dict[str, str] = {}
@@ -3298,7 +3298,7 @@ def open(
 
     preinit()
 
-    accept_warnings: list[str | bytes] = []
+    accept_warnings: list[str] = []
 
     def _open_core(
         fp: IO[bytes],
@@ -3313,8 +3313,8 @@ def _open_core(
             try:
                 factory, accept = OPEN[i]
                 result = not accept or accept(prefix)
-                if type(result) in [str, bytes]:
-                    accept_warnings.append(result)  # type: ignore[arg-type]
+                if isinstance(result, str):
+                    accept_warnings.append(result)
                 elif result:
                     fp.seek(0)
                     im = factory(fp, filename)
@@ -3350,7 +3350,7 @@ def _open_core(
     if exclusive_fp:
         fp.close()
     for message in accept_warnings:
-        warnings.warn(message)  # type: ignore[arg-type]
+        warnings.warn(message)
     msg = "cannot identify image file %r" % (filename if filename else fp)
     raise UnidentifiedImageError(msg)
 
@@ -3464,7 +3464,7 @@ def merge(mode, bands):
 def register_open(
     id,
     factory: Callable[[IO[bytes], str | bytes], ImageFile.ImageFile],
-    accept: Callable[[bytes], bool] | None = None,
+    accept: Callable[[bytes], bool | str] | None = None,
 ) -> None:
     """
     Register an image file plugin.  This function should not be used

src/PIL/Jpeg2KImagePlugin.py

@@ -313,7 +313,7 @@ def load(self):
         return ImageFile.ImageFile.load(self)
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return (
         prefix[:4] == b"\xff\x4f\xff\x51"
         or prefix[:12] == b"\x00\x00\x00\x0cjP  \x0d\x0a\x87\x0a"

src/PIL/JpegImagePlugin.py

@@ -344,7 +344,7 @@ def DQT(self, marker):
 }
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     # Magic number was taken from https://en.wikipedia.org/wiki/JPEG
     return prefix[:3] == b"\xFF\xD8\xFF"
 

src/PIL/MicImagePlugin.py

@@ -25,7 +25,7 @@
 # --------------------------------------------------------------------
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:8] == olefile.MAGIC
 
 

src/PIL/PngImagePlugin.py

@@ -689,7 +689,7 @@ def chunk_fdAT(self, pos, length):
 # PNG reader
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:8] == _MAGIC
 
 

src/PIL/PsdImagePlugin.py

@@ -44,7 +44,7 @@
 # read PSD images
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"8BPS"
 
 

src/PIL/QoiImagePlugin.py

@@ -13,7 +13,7 @@
 from ._binary import i32be as i32
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"qoif"
 
 

src/PIL/TiffImagePlugin.py

@@ -277,7 +277,7 @@
 ]
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] in PREFIXES
 
 

src/PIL/WebPImagePlugin.py

@@ -23,7 +23,7 @@
 }
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool | str:
     is_riff_file_format = prefix[:4] == b"RIFF"
     is_webp_file = prefix[8:12] == b"WEBP"
     is_valid_vp8_mode = prefix[12:16] in _VP8_MODES_BY_IDENTIFIER
@@ -34,6 +34,7 @@ def _accept(prefix):
                 "image file could not be identified because WEBP support not installed"
             )
         return True
+    return False
 
 
 class WebPImageFile(ImageFile.ImageFile):

src/PIL/WmfImagePlugin.py

@@ -65,7 +65,7 @@ def load(self, im):
 # Read WMF file
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return (
         prefix[:6] == b"\xd7\xcd\xc6\x9a\x00\x00" or prefix[:4] == b"\x01\x00\x00\x00"
     )

src/PIL/XpmImagePlugin.py

@@ -24,7 +24,7 @@
 xpm_head = re.compile(b'"([0-9]*) ([0-9]*) ([0-9]*) ([0-9]*)')
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:9] == b"/* XPM */"