[gvieira18]

With --output-format=json, the changed_files list can contain files that Rector did not change, while totals.changed_files counts only the real changes. The e2e applied-no-diffs-format-json of this PR, on main:

{
    "totals": {
        "changed_files": 1,
        "errors": 0
    },
    "changed_files": [
        "src/AliasedSameShortName.php",
        "src/AnonymousClassDocblock.php",
        "src/RemoveAlwaysElse.php",
        "src/global_class_constant_twice_without_namespace.php",
        "src/global_class_new_twice_without_namespace.php",
        "src/global_class_type_twice_without_namespace.php"
    ]
}

Only the file src/RemoveAlwaysElse.php should be changed.

A tool or a CI script that reads the list sees changes that do not exist. In a project I work on, a cold --dry-run with withImportNames() lists 92 files with totals.changed_files: 0. See rectorphp/rector#9911 for the same result on symfony/symfony and Sylius.

Cause

A rule or a post rector can record a line change and print identical code. FileProcessor then creates a FileDiff with an empty diff. This is on purpose (#6794): AbstractRectorTestCase uses it to warn about a rule that changes nothing. JsonOutputFactory lists every FileDiff, because with --no-diffs every diff is empty and the real changes must stay in the list (#7821).

The name importing post rectors cause it in different branches of their code, for example:

• a short name that is already in use, next to an aliased import with the same short name;
• a global class used two or more times in a file without a namespace;
• a fully qualified name in the docblock of an anonymous class.

A fix for one branch (#8512) leaves the others. This PR fixes the output instead, for all of them.

Change

• FileDiff gets a hasChanged flag, set from File::hasChanged(), the same source as totals.changed_files. The flag is serialized for the parallel workers.
• JsonOutputFactory lists a file only when hasChanged() is true. This works with and without --no-diffs.
• The empty FileDiff stays, so the [dx] add test to check that a rule is not applied if it does not change the code #6794 warning does not change.

Tests

• JsonOutputFactoryTest: an unchanged FileDiff is not listed with --no-diffs.
• FileDiffTest: the flag stays after the worker serialization.
• e2e applied-no-diffs-format-json: importNames() plus one file for each case above (5 files). Without the fix, the changed_files list also contains these 5 files, which Rector does not change.