[XAttrMetadata] Refactor and document dependencies

yt_dlp/utils.py

@@ -4673,87 +4673,56 @@ def decode_png(png_data):
 
 
 def write_xattr(path, key, value):
-    # This mess below finds the best xattr tool for the job
-    try:
-        # try the pyxattr module...
-        import xattr
+    # Windows: Write xattrs to NTFS Alternate Data Streams:
+    # http://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_.28ADS.29
+    if compat_os_name == 'nt':
+        assert ':' not in key
+        assert os.path.exists(path)
 
-        if hasattr(xattr, 'set'):  # pyxattr
-            # Unicode arguments are not supported in python-pyxattr until
-            # version 0.5.0
-            # See https://github.com/ytdl-org/youtube-dl/issues/5498
-            pyxattr_required_version = '0.5.0'
-            if version_tuple(xattr.__version__) < version_tuple(pyxattr_required_version):
-                # TODO: fallback to CLI tools
-                raise XAttrUnavailableError(
-                    'python-pyxattr is detected but is too old. '
-                    'yt-dlp requires %s or above while your version is %s. '
-                    'Falling back to other xattr implementations' % (
-                        pyxattr_required_version, xattr.__version__))
+        try:
+            with open(f'{path}:{key}', 'wb') as f:
+                f.write(value)
+        except OSError as e:
+            raise XAttrMetadataError(e.errno, e.strerror)
+        return
 
+    # UNIX Method 1. Use xattrs/pyxattrs modules
+    from .dependencies import xattr
+
+    setxattr = None
+    if getattr(xattr, '_yt_dlp__identifier', None) == 'pyxattr':
+        # Unicode arguments are not supported in pyxattr until version 0.5.0
+        # See https://github.com/ytdl-org/youtube-dl/issues/5498
+        if version_tuple(xattr.__version__) >= (0, 5, 0):
             setxattr = xattr.set
-        else:  # xattr
-            setxattr = xattr.setxattr
+    elif xattr:
+        setxattr = xattr.setxattr
 
+    if setxattr:
         try:
             setxattr(path, key, value)
         except OSError as e:
             raise XAttrMetadataError(e.errno, e.strerror)
+        return
 
-    except ImportError:
-        if compat_os_name == 'nt':
-            # Write xattrs to NTFS Alternate Data Streams:
-            # http://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_.28ADS.29
-            assert ':' not in key
-            assert os.path.exists(path)
+    # UNIX Method 2. Use setfattr/xattr executables
+    exe = ('setfattr' if check_executable('setfattr', ['--version'])
+           else 'xattr' if check_executable('xattr', ['-h']) else None)
+    if not exe:
+        raise XAttrUnavailableError(
+            'Couldn\'t find a tool to set the xattrs. Install either the python "xattr" or "pyxattr" modules or the '
+            + ('"xattr" binary' if sys.platform != 'linux' else 'GNU "attr" package (which contains the "setfattr" tool)'))
 
-            ads_fn = path + ':' + key
-            try:
-                with open(ads_fn, 'wb') as f:
-                    f.write(value)
-            except OSError as e:
-                raise XAttrMetadataError(e.errno, e.strerror)
-        else:
-            user_has_setfattr = check_executable('setfattr', ['--version'])
-            user_has_xattr = check_executable('xattr', ['-h'])
-
-            if user_has_setfattr or user_has_xattr:
-
-                value = value.decode('utf-8')
-                if user_has_setfattr:
-                    executable = 'setfattr'
-                    opts = ['-n', key, '-v', value]
-                elif user_has_xattr:
-                    executable = 'xattr'
-                    opts = ['-w', key, value]
-
-                cmd = ([encodeFilename(executable, True)]
-                       + [encodeArgument(o) for o in opts]
-                       + [encodeFilename(path, True)])
-
-                try:
-                    p = Popen(
-                        cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
-                except OSError as e:
-                    raise XAttrMetadataError(e.errno, e.strerror)
-                stdout, stderr = p.communicate_or_kill()
-                stderr = stderr.decode('utf-8', 'replace')
-                if p.returncode != 0:
-                    raise XAttrMetadataError(p.returncode, stderr)
-
-            else:
-                # On Unix, and can't find pyxattr, setfattr, or xattr.
-                if sys.platform.startswith('linux'):
-                    raise XAttrUnavailableError(
-                        "Couldn't find a tool to set the xattrs. "
-                        "Install either the python 'pyxattr' or 'xattr' "
-                        "modules, or the GNU 'attr' package "
-                        "(which contains the 'setfattr' tool).")
-                else:
-                    raise XAttrUnavailableError(
-                        "Couldn't find a tool to set the xattrs. "
-                        "Install either the python 'xattr' module, "
-                        "or the 'xattr' binary.")
+    value = value.decode('utf-8')
+    try:
+        p = Popen(
+            [exe, '-w', key, value, path] if exe == 'xattr' else [exe, '-n', key, '-v', value, path],
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+    except OSError as e:
+        raise XAttrMetadataError(e.errno, e.strerror)
+    stderr = p.communicate_or_kill()[1].decode('utf-8', 'replace')
+    if p.returncode:
+        raise XAttrMetadataError(p.returncode, stderr)
 
 
 def random_birthday(year_field, month_field, day_field):