Runner: allow suppressing "No files were checked" error

[schlndh]

Description

Fixes https://github.com/squizlabs/PHP_CodeSniffer/issues/3556

Suggested changelog entry

Added --allow-empty-file-list argument to suppress "No files were checked error".

Related issues/external references

Fixes https://github.com/squizlabs/PHP_CodeSniffer/issues/3556

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
  • [ ] This change is only breaking for integrators, not for external standards or end-users.
• [ ] Documentation improvement

PR checklist

• [x] I have checked there is no other PR open for the same change.
• [x] I have read the Contribution Guidelines.
• [x] I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• [x] I have added tests to cover my changes.
• [x] I have verified that the code complies with the projects coding standards.
• [ ] [Required for new sniffs] I have added XML documentation for the sniff.
• [ ] I have opened a sister-PR in the documentation repository to update the Wiki.

[jrfnl]

@schlndh Thanks for this PR.

Some feedback:

• Please include what you are trying to fix in the PR description. Your arguments in https://github.com/squizlabs/PHP_CodeSniffer/issues/3556#issuecomment-3393265341 make some sense, but should be included in the commit message.
• I'm not keen on adding this as a full-on CLI option. I believe this should be handled via a config option, same as other flags which influence the exit code. Can you explain why you added a CLI option instead of a config option ?

[schlndh]

@jrfnl

Can you explain why you added a CLI option instead of a config option ?

I plan to use it as a config option via <arg name="allow-empty-file-list"/> (mainly because of Phpstorm). But IMO having it as a configuration option only seems a bit inflexible. The default behavior makes sense if you run phpcs manually. So I can imagine someone adding --allow-empty-file-list to CI scripts, git hooks, ... but keeping the default behavior otherwise.

[jrfnl]

I plan to use it as a config option via <arg name="allow-empty-file-list"/> (mainly because of Phpstorm). But IMO having it as a configuration option only seems a bit inflexible. The default behavior makes sense if you run phpcs manually. So I can imagine someone adding --allow-empty-file-list to CI scripts, git hooks, ... but keeping the default behavior otherwise.

And that's perfectly possible with a config flag, just as well as with a CLI option, so I don't see why that would be a reason to have a CLI option.

[jrfnl]

For reference for anyone coming across this PR and wanting to understand the larger context:

• https://github.com/PHPCSStandards/PHP_CodeSniffer/wiki/Version-4.0-User-Upgrade-Guide#my-scans-are-failing-on-a-no-files-were-checked-error
• https://github.com/squizlabs/PHP_CodeSniffer/issues/1595
• https://github.com/PHPCSStandards/PHP_CodeSniffer/pull/1023