Substitute %(default)s in ini option help text (#9244)#14556
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Command-line options added with `addoption` already expand `%(default)s` in their help text to the option's default value, because argparse does it. Ini options added with `addini` are rendered by pytest itself in `showhelp()`, so the token was shown literally in `pytest --help`. Replace `%(default)s` with the option's default when rendering ini help. A targeted string replace (instead of `%`-formatting) is used so help texts containing a literal `%` keep working. Closes pytest-dev#9244. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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I think an exact replacement for %(default)s is quite the hack. According to the Python documentation, other replacements work (type, prog, etc. etc.), so why should one of them work but not others? Also it seems unexpected that this uses the Python percent formatting syntax but then behaves differently for raw % signs.
I can see the importance of keeping backwards compat however, so maybe this needs something like a interpolate_help=True flag or somesuch (which is False by default)?
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Fixes #9244.
Command-line options added with
addoptionalready expand%(default)sin their help to the default value (argparse does this). Ini options added withaddiniare rendered by pytest itself inshowhelp(), so%(default)sshowed up literally inpytest --help.This PR replaces
%(default)swith the option's default value when rendering the ini help. I used a targetedstr.replacerather than%-formatting, so help texts that contain a literal%are not affected.Changes
helpconfig.py: substitute%(default)swith the ini option's default inshowhelp().config/argparsing.py: document thehelpparameter ofaddini.testing/test_helpconfig.py: add a regression test.9244.improvement.rst).