version/parser: speed up StemParser

[Bo98]

An I/O operation in a version parser is pretty unusual and, unsurprisingly, does show up in flame graphs when doing a lot of version parsing (though the I/O operation itself isn't too expensive).

The check was added in 355bfc1 but seems obsolete to me after extname was adjusted in 8b5fa68. It seems to have additionally also be handled with a5a1b29.

There was a unit test added in a06bd4e that did test the behaviour I am removing but it seems to be very focussed on what StemParser previously did internally rather than what it was intended to do to the broader version parsing system. Indeed the version number actually returned from Version.parse on that test sample remains the same even with the special StemParser logic removed.

Removing the directory check should also avoid the scenario where version parsing behaved differently if you happen to have a directory in your PWD that matches the input to the parser.

For this change I did the following:

export HOMEBREW_NO_INSTALL_FROM_API=1

brew info --json=v2 --formulae | jq '.formulae[] | "\(.name) \(.versions.stable) \(.versions.head)"'
brew info --json=v2 --casks | jq '.casks[] | "\(.token) \(.version)"'

and did not find any changes between the outputs with and without this change.

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[Copilot]

Pull request overview

This PR removes an unnecessary filesystem I/O check from Version::StemParser to speed up version parsing and avoid parsing behavior depending on whether a matching directory happens to exist on disk.

Changes:

• Remove spec.directory? short-circuit from Version::StemParser.process_spec, eliminating a filesystem stat during parsing.
• Remove the unit test that asserted the old “directories are returned as basename” behavior, aligning tests with the new deterministic parsing behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/version/parser.rb	Removes the directory existence check in StemParser to avoid I/O and keep parsing purely string-based.
Library/Homebrew/test/version/parser_spec.rb	Drops the directory-focused spec that validated the removed behavior.

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[MikeMcQuaid]

Thanks!