Using Rector for checking codebase before upgrade from 8.1 to 8.4

[FlyveHest]

I've been tasked with the laborious task of verifying our codebase and found Rector which looks like it will be a great tool for helping this process along.

So, I tried installing it, running it and fiddling a bit with the config, but got some unexpected results, so I tried just making a simple test project to see how Rector runs, and i'm not sure if i've done something completely wrong (most probable), or Rector just doesn't work.

The only file i've included in the project is this

<?php
  $value = utf8_decode('string');

composer.json is requiring php 8.1, Rector is set to run with ->withPhpSets(php82: true), and when I run list-rules, the following rule is included Rector\Php82\Rector\FuncCall\Utf8DecodeEncodeToMbConvertEncodingRector

BUT, when I run Rector, this is what I get:

> ./vendor/bin/rector --dry-run --debug
[file] .../test/test.php

[OK] Rector is done!

I would expect this rule to trigger, and it doesn't, and I don't understand why.

[TomasVotruba]

The composer.json has main priority when it comes to PHP version.

It protects your project from breakign changes that work only on PHP 8.2 and higher.

You can change your PHP version in composer.json or in rector.php - https://getrector.com/documentation/php-version-features

[FlyveHest]

Ahhh, so I need to change the version of the composer json to the target version i'm testing for, and yes, that works.

I thought I had to specify the tests to run in the rector config.

Thanks for the quick reply 👍