[aryansk]

Fixes #133049

Problem

Tools/i18n/pygettext.py diverges from GNU xgettext in two empty-input cases:

1. No input file given — xgettext prints xgettext: no input file given and Try 'xgettext --help' … with exit 1. pygettext silently generated an empty messages.pot with only a header.

2. No messages to extract — xgettext produces no output when no strings are found. pygettext still wrote a header-only messages.pot.

Issue #133049 reports both; tomasr8 confirmed the first is clear and should be fixed (input file should be required), while the second is debated but the issue requests xgettext-compatible behavior.

Change

• In Tools/i18n/pygettext.py:main() — after expanding args via getFilesForName, check if not args: → usage(1, "pygettext: no input file given\nTry 'pygettext --help' for more information.")

• After visiting files, check if not visitor.messages: → verbose message to stderr and sys.exit(0) without creating/writing the output file (covers both -o FILE and - stdout cases). This matches xgettext's "no output is generated if there are no messages".

Keep unrelated cleanup out of this PR.

Why this approach

Minimal, xgettext-compatible, and respects the maintainer's lean: the first fix is uncontroversial and matches the exact xgettext error wording; the second implements the requested "no empty output" while remaining silent unless -v is given, so existing workflows that expect an empty POT can be detected via the exit and verbose hint.

Testing

command: python3.14 Tools/i18n/pygettext.py (no args)
result: prints __doc__ + "pygettext: no input file given\nTry 'pygettext --help' …" to stderr, exit 1 — matches xgettext

command: echo 'print("hello")' > /tmp/test.py && python3.14 Tools/i18n/pygettext.py -o /tmp/out.pot /tmp/test.py; ls /tmp/out.pot
result: no out.pot created, exit 0

command: echo '_("hello")' > /tmp/test2.py && python3.14 Tools/i18n/pygettext.py -o /tmp/out2.pot /tmp/test2.py; cat /tmp/out2.pot
result: header + msgid "hello" written correctly

command: python3.14 -m py_compile Tools/i18n/pygettext.py
result: ok (3.13/3.14; 3.9 fails on unrelated PEP 701 f-string syntax already on main)

command: git diff --check
result: clean

make check for pygettext is covered by test.test_tools.test_i18n (skipped in this env due to missing build dir, but git diff --check and manual checks pass).

Documentation and release impact

• User-facing behavior updated (CLI error / empty-output)
• Changelog/release note needed: bug fix, no docs
• Migration or compatibility note needed
• No documentation impact

Review notes

• Known limitations: verbose-only hint for empty-messages case
• Follow-up issue, if any: none
• Security/licensing considerations: none

• Issue: pygettext generates output even when there should be none #133049