Incorrect behavior of DisallowedEmptyRuleFixerRector with uninitialized properties

[nerones]

Bug Report

Subject	Details
Rector version	last dev-main
Installed as	composer dependency

Minimal PHP Code Causing Issue

See https://getrector.com/demo/7e222012-b871-4e3c-9b05-3a62017753f7

<?php

final class DemoFile
{
    protected string $test;
    
    public function run()
    {
        return empty($this->test);
    }
}

Responsible rules

• DisallowedEmptyRuleFixerRector

Expected Behavior

The code must not change.

The problem with this rule is that is not safe to compare against an empty string because the property it's not initialized. The empty function will also check for not initialized properties. The same thing will happen with other types.

[samsonasik]

empty() usage is not recommended on strict usage, see https://phpstan.org/r/e0c34868-f3b5-481d-821e-5499e6d0253d

I think the correct usage is to change with isset early on unitialized property:

-return empty($this->test);
+return ! isset($this->test) || $this->test === '':

[nerones]

You are right, what you propose is a better solution.

[TomasVotruba]

@samsonasik Could you handle this one? Thanks 👍

[samsonasik]

I will try

[samsonasik]

Resolved at PR:

• [Strict] Handle may be unitialized property on DisallowedEmptyRuleFixerRector rector-src#5409