For Python 3.13: A drop-in replacement for imghdr.what()

magic/__init__.py

@@ -15,6 +15,7 @@
 >>>
 
 """
+from __future__ import annotations
 
 import sys
 import os
@@ -398,6 +399,39 @@ def magic_getparam(cookie, param):
     return val.value
 
 
+# Convert magic extensions to imghdr extensions
+imghdr_exts = {"ascii": None, "data": None, "iso-8859": None, "openexr": "exr", "riff": "webp", "sgi": "rgb", "sun": "rast"}  # , "jpeg": "jpg", "jpg": "jpeg", "openexr": "exr", "sgi": "rgb", "sun": "rast", "riff": "webp", "tif": "tiff"}
+
+
+def what(file: os.PathLike | str | None, h: bytes | None) -> str:
+    """A drop-in replacement for `imghdr.what()` which was removed from the standard
+    library in Python 3.13.
+    Usage:
+    ```python
+    # Replace...
+    from imghdr import what
+    # with...
+    from magic import what
+    # ---
+    # Or replace...
+    import imghdr
+    ext = imghdr.what(...)
+    # with...
+    import magic
+    ext = magic.what(...)
+    ```
+    imghdr documentation: https://docs.python.org/3.12/library/imghdr.html
+    imghdr source code: https://github.com/python/cpython/blob/3.12/Lib/imghdr.py
+    """
+    if not h:
+        return from_file(file).split()[0].lower()
+
+    if isinstance(h, str):
+        h = bytes.fromhex(h)
+    ext = from_buffer(h).split()[0].lower()
+    return imghdr_exts.get(ext, ext)
+
+
 _has_version = False
 if hasattr(libmagic, "magic_version"):
     _has_version = True

magic/loader.py

@@ -12,7 +12,8 @@ def _lib_candidates_linux():
 
     This is necessary because alpine is bad
     """
-    yield "libmagic.so.1"
+    for filename in ("libmagic.so", "libmagic.so.1"):
+        yield find_library(filename)
 
 
 def _lib_candidates_macos():

test/test_what.py

@@ -0,0 +1,135 @@
+from __future__ import annotations
+
+from pathlib import Path
+from sys import version_info
+from warnings import filterwarnings
+
+import pytest
+
+from magic import what
+
+filterwarnings("ignore", message="'imghdr' is deprecated")
+try:  # imghdr was removed from the standard library in Python 3.13
+    from imghdr import what as imghdr_what
+except ModuleNotFoundError:
+    imghdr_what = None
+
+# file_tests = sorted(test_func.__name__[5:] for test_func in imghdr.tests)
+# file_tests = "bmp exr gif jpg pbm pgm png ppm ras rgb tif webp xbm".split()
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize("file", [
+    "keep-going.jpg",
+    "name_use.jpg"
+])
+def test_what_from_file(file, h=None):
+    """Run each test with a path string and a pathlib.Path."""
+    # expected = file.split(".")[-1]
+    # if expected == "jpeg":
+    #     expected = "jpg"
+    file = f"test/testdata/{file}"
+    assert what(file, h) == imghdr_what(file, h)
+    file = Path(file).resolve()
+    assert what(file, h) == imghdr_what(file, h)
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+def ztest_what_from_file_none(file="test/resources/fake_file", h=None):
+    assert what(file, h) == imghdr_what(file, h) is None
+    file = Path(file).resolve()
+    assert what(file, h) == imghdr_what(file, h) is None
+
+
+string_tests = [
+    ("exr", "762f3101"),
+    ("exr", b"\x76\x2f\x31\x01"),
+    ("gif", "474946383761"),
+    ("gif", b"GIF87a"),
+    ("gif", b"GIF89a"),
+    ("rast", b"\x59\xA6\x6A\x95"),
+    ("rgb", b"\001\332"),
+    ("webp", b"RIFF____WEBP"),
+    (None, "decafbad"),
+    (None, b"decafbad"),
+]
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize("expected, h", string_tests)
+def test_what_from_string(expected, h):
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert imghdr_what(None, h) == what(None, h) == expected
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize(
+    "expected, h",
+    [
+        ("jpeg", "ffd8ffdb"),
+        ("jpeg", b"\xff\xd8\xff\xdb"),
+    ],
+)
+def test_what_from_string_py311(expected, h):
+    """
+    These tests fail with imghdr on Python < 3.11.
+    TODO: (cclauss) Document these imghdr fails on Python < 3.11
+    """
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert what(None, h) == expected
+    if version_info < (3, 11):  # TODO: Document these imghdr fails
+        expected = None
+    assert imghdr_what(None, h) == expected
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize(
+    "expected, h",
+    [
+        ("bmp", "424d"),
+        ("bmp", "424d787878785c3030305c303030"),
+        ("bmp", b"BM"),
+        ("jpeg", b"______JFIF"),
+        ("jpeg", b"______Exif"),
+        ("pbm", b"P1 "),
+        ("pbm", b"P1\n"),
+        ("pbm", b"P1\r"),
+        ("pbm", b"P1\t"),
+        ("pbm", b"P4 "),
+        ("pbm", b"P4\n"),
+        ("pbm", b"P4\r"),
+        ("pbm", b"P4\t"),
+        ("pgm", b"P2 "),
+        ("pgm", b"P2\n"),
+        ("pgm", b"P2\r"),
+        ("pgm", b"P2\t"),
+        ("pgm", b"P5 "),
+        ("pgm", b"P5\n"),
+        ("pgm", b"P5\r"),
+        ("pgm", b"P5\t"),
+        ("png", "89504e470d0a1a0a"),
+        ("png", b"\211PNG\r\n\032\n"),
+        ("ppm", b"P3 "),
+        ("ppm", b"P3\n"),
+        ("ppm", b"P3\r"),
+        ("ppm", b"P3\t"),
+        ("ppm", b"P6 "),
+        ("ppm", b"P6\n"),
+        ("ppm", b"P6\r"),
+        ("ppm", b"P6\t"),
+        ("tiff", b"II"),
+        ("tiff", b"MM"),
+        ("xbm", b"#define "),
+    ],
+)
+def test_what_from_string_todo(expected, h):
+    """
+    These tests pass with imghdr but fail with magic.
+    TODO: (cclauss) Fix these magic fails
+    """
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert imghdr_what(None, h) == expected
+    assert what(None, h) is None