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

[shivamtiwari3]

Summary

Fixes #454.

Short flags like -f and -s were being stored directly in **kwargs (as {'f': 'hello', 's': 'world'}) instead of being expanded to their matching positional argument names (first_arg, second_arg) when a function accepts **kwargs.

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Problem

In _ParseKeywordArgs (core.py:887), the condition was:

if (key in fn_args
    or (is_bool_syntax and key.startswith('no') and key[2:] in fn_args)
    or fn_keywords):
  keyword = key
elif len(key) == 1:
  # single-char shortcut lookup ...

When fn_keywords is truthy (i.e. the function has **kwargs), the first branch fires immediately, setting keyword = key (the raw single character). The shortcut lookup in the elif branch is never reached.

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Solution

Restructured the conditions so single-char shortcut expansion against fn_args is always attempted first. fn_keywords is only used as a fallback when no fn_arg matches the single character:

if key in fn_args or (...noXxx... in fn_args):
  keyword = key
elif len(key) == 1:
  matching_fn_args = [arg for arg in fn_args if arg[0] == key]
  if len(matching_fn_args) == 1:
    keyword = matching_fn_args[0]
  elif len(matching_fn_args) > 1:
    raise FireError(...)
  elif fn_keywords:      # ← fallback: no fn_arg match, accept into **kwargs
    keyword = key
elif fn_keywords:
  keyword = key

Multi-character unrecognised flags still fall through to **kwargs as before.

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Testing

• Added fn_with_defaults_and_kwargs to test_components.py
• Added testSingleCharFlagParsingWithKwargs to fire_test.py covering:
  • -f=hello -s=world → ('hello', 'world', {})
  • -f hello -s world → ('hello', 'world', {})
  • unrecognised --unknown_key=42 → still forwarded to **kwargs
• Command: python3 -m pytest fire/ --ignore=fire/docstrings_fuzz_test.py --ignore=fire/parser_fuzz_test.py
• 261 tests pass, 0 failures

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Checklist

• Fixes the reported issue
• Existing behaviour unchanged (no regressions)
• Tests added
• All 261 tests pass
• Code style matches project conventions