[Kanti]

Q	A
Branch	v2.x
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Documented?	yes
Fixed tickets	-

PHPStan 2.3.5 made many built-in errors auto-fixable (e.g. method.missingOverride, cast.useless, phpunit.*). It marks them with 🔧 and ends its report with "Run PHPStan again with --fix".

This PR plugs that into GrumPHP's fixer the same way as the other fixable tasks (ECS, Rector, Mago): when the analysis fails and PHPStan reports fixable errors, the phpstan task returns a FixableTaskResult that reruns the same phpstan analyse command with --fix (same files, configuration, level and memory limit).

Why only when PHPStan reports fixable errors?

• Most PHPStan errors (e.g. type errors) cannot be fixed automatically. In that case phpstan analyse --fix exits with 1 and "No fixable errors found", so GrumPHP would ask to fix and then report a failing fixer.
• Older PHPStan versions never print the hint, so they keep the current behaviour. (In PHPStan ≤ 2.1, --fix launched PHPStan Pro instead of fixing.)

The hint for fixable ignored errors (--fix-ignored) is deliberately not taken into account, since ignored errors don't make the task fail. If PHPStan ever rewords the hint, the task falls back to the current non-fixable behaviour.

Tested manually against the PHPStan phars

• 2.3.5 with a fixable and a non-fixable error: --fix exits with 0 even though the non-fixable error remains, the fixer reports ✔ and only #[\Override] was added.
• 2.3.5 with only non-fixable errors: no fixer offered.
• 2.3.4: no fixer offered, behaviour unchanged.
• PHPStan passes the given paths on to its fix rounds, so only the files analysed by GrumPHP are changed.

The docs mention that --fix is experimental in PHPStan and also removes unmatched ignoreErrors entries from the configuration/baseline and unmatched @phpstan-ignore comments.

New Task Checklist:

• Are the dependencies added to the composer.json suggestions? (phpstan/phpstan is already suggested)
• Is the doc/tasks.md file updated? (PHPStan is already listed, no change needed)
• Are the task parameters documented? (no new parameters, the auto-fixing behaviour is documented in doc/tasks/phpstan.md)
• Is the task registered in the tasks.yml file? (already registered)
• Does the task contains phpunit tests? (test/Unit/Task/PhpStanTest.php covers fixable, non-fixable and fixable-ignored output and the fix command)
• Is the configuration having logical allowed types? (configuration unchanged)
• Does the task run in the correct context? (unchanged: pre-commit and run)
• Is the run() method readable?
• Is the run() method using the configuration correctly? (the fix command reuses the same arguments)
• Are all CI services returning green?