Only apply UTF-8 monkey patch when necessary (#3573)

* Apply the UTF-8 locale patch only when necessary

* Cleanup args

* Only apply input/output patches when the handler is callable

* zzz

* Flake8 fix

* removed trailing spaces

medusa/init/filesystem.py

@@ -80,9 +80,32 @@ def _varkwargs(**kwargs):
     return {k: _handle_input(arg) for k, arg in kwargs.items()}
 
 
-def make_closure(f, handle_arg, handle_output):
-    """Create a closure that encodes parameters to utf-8 and call original function."""
-    return lambda *args, **kwargs: handle_output(f(*[handle_arg(arg) for arg in args], **{k: handle_arg(arg) for k, arg in kwargs.items()}))
+def make_closure(f, handle_arg=None, handle_output=None):
+    """Apply an input handler and output handler to a function.
+
+    Used to ensure UTF-8 encoding at input and output.
+    """
+    return patch_output(patch_input(f, handle_arg), handle_output)
+
+
+def patch_input(f, handle_arg=None):
+    """Patch all args and kwargs of function f.
+
+    If handle_arg is None, just return the original function.
+    """
+    def patched_input(*args, **kwargs):
+        return f(*[handle_arg(arg) for arg in args], **{k: handle_arg(arg) for k, arg in kwargs.items()})
+    return patched_input if callable(handle_arg) else f
+
+
+def patch_output(f, handle_output=None):
+    """Patch the output of function f with the handle_output function.
+
+    If handle_output is None, just return the original function.
+    """
+    def patched_output(*args, **kwargs):
+        return handle_output(f(*args, **kwargs))
+    return patched_output if callable(handle_output) else f
 
 
 def initialize():
@@ -113,9 +136,12 @@ def initialize():
     if os.name != 'nt':
         affected_functions[os].extend(['chmod', 'chown', 'link', 'statvfs', 'symlink'])
 
-    handle_arg = _handle_input if not fs_encoding or fs_encoding.lower() != 'utf-8' else lambda x: x
+    if not fs_encoding or fs_encoding.lower() != 'utf-8':
+        handle_input = _handle_input
+    else:
+        handle_input = None
 
     for k, v in affected_functions.items():
         handle_output = handle_output_map.get(k, _handle_output_u)
         for f in v:
-            setattr(k, f, make_closure(getattr(k, f), handle_arg, handle_output))
+            setattr(k, f, make_closure(getattr(k, f), handle_input, handle_output))