loader.py: Separate functions for each operating system

magic/loader.py

@@ -4,47 +4,65 @@
 import glob
 import os.path
 
-def _lib_candidates():
 
-  yield find_library('magic')
+def _lib_candidates_linux():
+    """Yield possible libmagic library names on Linux.
+
+    This is necessary because alpine is bad
+    """
+    yield "libmagic.so.1"
 
-  if sys.platform == 'darwin':
 
+def _lib_candidates_macos():
+    """Yield possible libmagic library names on macOS."""
     paths = [
-      '/opt/local/lib',
-      '/usr/local/lib',
-      '/opt/homebrew/lib',
-    ] + glob.glob('/usr/local/Cellar/libmagic/*/lib')
+        "/opt/homebrew/lib",
+        "/opt/local/lib",
+        "/usr/local/lib",
+    ] + glob.glob("/usr/local/Cellar/libmagic/*/lib")
+    for path in paths:
+        yield os.path.join(path, "libmagic.dylib")
 
-    for i in paths:
-      yield os.path.join(i, 'libmagic.dylib')
 
-  elif sys.platform in ('win32', 'cygwin'):
+def _lib_candidates_windows():
+    """Yield possible libmagic library names on Windows."""
+    prefixes = (
+        "libmagic",
+        "magic1",
+        "magic-1",
+        "cygmagic-1",
+        "libmagic-1",
+        "msys-magic-1",
+    )
+    for prefix in prefixes:
+        # find_library searches in %PATH% but not the current directory,
+        # so look for both
+        yield "./%s.dll" % (prefix,)
+        yield find_library(prefix)
 
-    prefixes = ['libmagic', 'magic1', 'magic-1', 'cygmagic-1', 'libmagic-1', 'msys-magic-1']
 
-    for i in prefixes:
-      # find_library searches in %PATH% but not the current directory,
-      # so look for both
-      yield './%s.dll' % (i,)
-      yield find_library(i)
+def _lib_candidates():
+    yield find_library("magic")
 
-  elif sys.platform == 'linux':
-    # This is necessary because alpine is bad
-    yield 'libmagic.so.1'
+    func = {
+        "cygwin": _lib_candidates_windows,
+        "darwin": _lib_candidates_macos,
+        "linux": _lib_candidates_linux,
+        "win32": _lib_candidates_windows,
+    }[sys.platform]
+    # When we drop legacy Python, we can just `yield from func()`
+    for path in func():
+        yield path
 
 
 def load_lib():
+    for lib in _lib_candidates():
+        # find_library returns None when lib not found
+        if lib:
+            try:
+                return ctypes.CDLL(lib)
+            except OSError:
+                pass
 
-  for lib in _lib_candidates():
-    # find_library returns None when lib not found
-    if lib is None:
-      continue
-    try:
-      return ctypes.CDLL(lib)
-    except OSError:
-      pass
-  else:
     # It is better to raise an ImportError since we are importing magic module
-    raise ImportError('failed to find libmagic.  Check your installation')
-
+    raise ImportError("failed to find libmagic.  Check your installation")