False positive for UnusedPrivateMethod when method is called on clone

[sveneld]

• PHPMD version: 2.11.0
• PHP Version: 7.4.3
• Installation type: composer
• Operating System / Distribution & Version: Ubuntu 20.04.3 LTS

Current Behavior

<?php

class Test
{

    private $keywords = [];

    public function testClone()
    {
        $clone = clone $this;
        $clone->prepareKeywords();

        return $clone;
    }

    private function prepareKeywords()
    {
        $this->keywords = ['a', 'b'];
    }
}

phpmd: Avoid unused private methods such as 'prepareKeywords'.

Expected Behavior

No error

Steps To Reproduce:

Run phpmd inspection on provided code

[tvbeek]

@sveneld thanks for your report, this is an interesting case. If this function is only used after the clone I should personal use the __ clone function. See: https://www.php.net/clone
I'm not sure if we can check this correct, do you have the possibility to create a PR with a failing test? That can be a nice starting point.

ps. I have edited your post to have the code highlighting working.

[sveneld]

Ok, I will try to create PR with failing test

[sveneld]

@tvbeek #940 here it is

[cs278]

Basically the problem (using 2.12.0), by creating a new instance in a static method:

Avoid unused private methods such as 'doThing'

final class Test
{
    public static function create(): self
    {
        $obj = new self();
        $obj->doThing();

        return $obj;
    }

    private function doThing(): void
    {
    }
}