Fix short flags being swallowed by **kwargs (fixes #454)

fire/core.py

@@ -884,12 +884,13 @@ def _ParseKeywordArgs(args, fn_spec):
 
       # Determine the keyword.
       keyword = ''  # Indicates no valid keyword has been found yet.
-      if (key in fn_args
-          or (is_bool_syntax and key.startswith('no') and key[2:] in fn_args)
-          or fn_keywords):
+      if key in fn_args or (
+          is_bool_syntax and key.startswith('no') and key[2:] in fn_args):
         keyword = key
       elif len(key) == 1:
-        # This may be a shortcut flag.
+        # This may be a shortcut flag. Check fn_args before falling back to
+        # fn_keywords so that short flags like -f expand to the matching
+        # fn_arg (e.g. 'first_arg') even when **kwargs is present.
         matching_fn_args = [arg for arg in fn_args if arg[0] == key]
         if len(matching_fn_args) == 1:
           keyword = matching_fn_args[0]
@@ -898,6 +899,10 @@ def _ParseKeywordArgs(args, fn_spec):
               f"The argument '{argument}' is ambiguous as it could "
               f"refer to any of the following arguments: {matching_fn_args}"
           )
+        elif fn_keywords:
+          keyword = key
+      elif fn_keywords:
+        keyword = key
 
       # Determine the value.
       if not keyword:

fire/fire_test.py

@@ -491,6 +491,23 @@ def testSingleCharFlagParsingExactMatch(self):
         fire.Fire(tc.SimilarArgNames,
                   command=['identity2', '-a', '-alpha']), (True, True))
 
+  def testSingleCharFlagParsingWithKwargs(self):
+    # Short flags should map to their matching fn_arg even when **kwargs is
+    # present (regression test for github.com/google/python-fire/issues/454).
+    self.assertEqual(
+        fire.Fire(tc.fn_with_defaults_and_kwargs,
+                  command=['-f=hello', '-s=world']),
+        ('hello', 'world', {}))
+    self.assertEqual(
+        fire.Fire(tc.fn_with_defaults_and_kwargs,
+                  command=['-f', 'hello', '-s', 'world']),
+        ('hello', 'world', {}))
+    # Unrecognised single-char flags should still be forwarded to **kwargs.
+    self.assertEqual(
+        fire.Fire(tc.fn_with_defaults_and_kwargs,
+                  command=['--unknown_key=42']),
+        ('left', 'right', {'unknown_key': 42}))
+
   def testSingleCharFlagParsingCapitalLetter(self):
     self.assertEqual(
         fire.Fire(tc.CapitalizedArgNames,

fire/test_components.py

@@ -556,6 +556,11 @@ def fn_with_kwarg_and_defaults(arg1, arg2, opt=True, **kwargs):
   return kwargs.get('arg3')
 
 
+def fn_with_defaults_and_kwargs(first_arg='left', second_arg='right', **kwargs):
+  """Function with named defaults plus **kwargs, used to test short flags."""
+  return (first_arg, second_arg, kwargs)
+
+
 def fn_with_multiple_defaults(first='first', last='last', late='late'):
   """Function with kwarg and defaults.