Add fsdecode as a wrapper for os.fsdecode and clean filename handling

os.fsdecode was introduced in python 3.2, so I implemented fsdecode in
utils.py to be able to use it on previous versions. fsdecode thus
returns the filename passed as parameter as a unicode string (either
if it's str or bytes), and if a PathLike object is used, it returns
its filename. In other case, it raises a TypeError exception.

Changed code in from_file and mediainfo_json to use it, which simplifies
the code a bit and hopefully fixes the last windows appveyor error.

pydub/audio_segment.py

@@ -8,7 +8,7 @@
 import sys
 import struct
 from .logging_utils import log_conversion, log_subprocess_output
-from .utils import mediainfo_json
+from .utils import mediainfo_json, fsdecode
 import base64
 from collections import namedtuple
 
@@ -492,13 +492,7 @@ def from_mono_audiosegments(cls, *mono_segments):
 
     @classmethod
     def from_file_using_temporary_files(cls, file, format=None, codec=None, parameters=None, **kwargs):
-        try:
-            if isinstance(file, os.PathLike):
-                orig_file = os.fspath(file)
-            else:
-                orig_file = file
-        except AttributeError:
-            orig_file = file
+        orig_file = file
         file = _fd_or_path_or_tempfile(file, 'rb', tempfile=False)
 
         if format:
@@ -595,13 +589,11 @@ def is_format(f):
 
     @classmethod
     def from_file(cls, file, format=None, codec=None, parameters=None, **kwargs):
+        orig_file = file
         try:
-            if isinstance(file, os.PathLike):
-                orig_file = os.fspath(file)
-            else:
-                orig_file = file
-        except AttributeError:
-            orig_file = file
+            filename = fsdecode(file)
+        except TypeError:
+            filename = None
         file = _fd_or_path_or_tempfile(file, 'rb', tempfile=False)
 
         if format:
@@ -612,10 +604,10 @@ def is_format(f):
             f = f.lower()
             if format == f:
                 return True
-            if isinstance(orig_file, basestring):
-                return orig_file.lower().endswith(".{0}".format(f))
-            if isinstance(orig_file, bytes):
-                return orig_file.lower().endswith((".{0}".format(f)).encode('utf8'))
+
+            if filename:
+                return filename.lower().endswith(".{0}".format(f))
+
             return False
 
         if is_format("wav"):
@@ -648,8 +640,8 @@ def is_format(f):
             # force audio decoder
             conversion_command += ["-acodec", codec]
 
-        if isinstance(orig_file, (basestring, bytes)):
-            conversion_command += ["-i", orig_file]
+        if filename:
+            conversion_command += ["-i", filename]
             stdin_parameter = None
             stdin_data = None
         else:

pydub/utils.py

@@ -202,21 +202,38 @@ def get_prober_name():
         return "ffprobe"
 
 
+def fsdecode(filename):
+    """Wrapper for os.fsdecode which was introduced in python 3.2 ."""
+
+    if sys.version_info >= (3, 2):
+        PathLikeTypes = (basestring, bytes)
+        if sys.version_info >= (3, 6):
+            PathLikeTypes += (os.PathLike,)
+        if isinstance(filename, PathLikeTypes):
+            return os.fsdecode(filename)
+    else:
+        if isinstance(filename, bytes):
+            return filename.decode(sys.getfilesystemencoding())
+        if isinstance(filename, basestring):
+            return filename
+
+    raise TypeError("type {0} not accepted by fsdecode".format(type(filename)))
+
+
 def mediainfo_json(filepath):
     """Return json dictionary with media info(codec, duration, size, bitrate...) from filepath
     """
-
     prober = get_prober_name()
     command_args = [
         "-v", "info",
         "-show_format",
         "-show_streams",
     ]
-    if isinstance(filepath, (basestring, bytes)):
-        command_args += [filepath]
+    try:
+        command_args += [fsdecode(filepath)]
         stdin_parameter = None
         stdin_data = None
-    else:
+    except TypeError:
         command_args += ["-"]
         stdin_parameter = PIPE
         file = _fd_or_path_or_tempfile(filepath, 'rb', tempfile=False)