[mechgw]

What:

• Bug Fix
• New Feature

Description:

A mutator that is not part of a default set never creates a mutation, even when it is requested explicitly. For example, pest --mutate --mutator=StringNotEmptyStringToEmpty (or ->mutator(Mutators::STRING_NOT_EMPTY_STRING_TO_EMPTY)) reports 0 Mutations for 0 Files created on code full of non-empty strings.

MutationGenerator::filterMutators() keeps only the requested mutators found in MutatorMap, and MutatorMap is built from the default sets. NotEmptyStringToEmpty is commented out in StringSet, so it is never in the map, and the requested mutator is silently dropped.

The fix. filterMutators() keeps each requested mutator whose nodesToHandle() contains a node type of the file. That is the same check the map performed, but it no longer depends on the default sets. The default sets are unchanged, so nothing changes for users who do not request such a mutator.

After this change MutatorMap is no longer used by the plugin. I left it in place because it is a public class; I am happy to remove it in this PR if you prefer.

Tests. it generates mutations of a mutator requested outside the default sets in tests/Unit/MutationGeneratorTest.php generates one mutation with NotEmptyStringToEmpty; without the fix it generates none.

CI. The workflows ran on a fork with the full matrix and fail-fast: false. COMPOSER_ROOT_VERSION=5.x-dev was set there only because Composer cannot guess the root version of a feature branch. The results were compared, job by job, with the same workflows on unmodified 5.x (d0c8711):

• this branch: Tests, Static Analysis
• 5.x: Tests, Static Analysis

The set of failures is identical in every job:

• the 3 Tests\Visual\* snapshots fail in the prefer-stable jobs, because current PHPUnit prints a deprecation warning for the cacheResult attribute of phpunit.xml;
• PHPStan reports 2 errors, both in files this PR does not touch.

Everything else passes.

🤖 Generated with Claude Code

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[mechgw]

For context: this is the first part of a fix for enum case values, which are never mutation-tested. The whole plan is described in pestphp/pest#1978.