willReturnCallback() does not pass unknown named variadic arguments to callback

[stefanfisk]

Q	A
PHPUnit version	10.2.6
PHP version	8.2.8
Installation Method	Composer

Summary

Mocks for methods that accept var args do not passed unknown named variadic arguments to the callback in willReturnCallback(). AFAIK this should be supported since PHP 8.0.0.

I believe the issue exists because the mocks use func_*() for getting the passed arguments, but those functions no longer return all arguments. See func_get_args() for details.

Current behavior

Only indexed arguments are passed.

How to reproduce

Here's two passing tests for unmocked cases and a failing test that uses a mock.

tests/Support/VarArger.php

<?php

namespace Tests\Support;

class VarArger
{
    public function fn(mixed ...$args): mixed
    {
        return [$foo, ...$args];
    }
}

tests/WithReturnCallbackTest.php

<?php

namespace Tests;

use PHPUnit\Framework\TestCase;
use Tests\Support\VarArger;
use stdClass;

class WithReturnCallbackTest extends TestCase
{
    public function testRealInstance(): void
    {
        $real = new VarArger();

        $args = ['foo', 'bar', 'baz' => 'qux'];

        $this->assertSame(
            $args,
            $real->fn(...$args),
        );
    }

    public function testCallback(): void
    {
        $callback = fn ($foo, ...$args) => [$foo, ...$args];

        $args = ['foo', 'bar', 'baz' => 'qux'];

        $this->assertSame(
            $args,
            $callback(...$args),
        );
    }

    public function testMock(): void
    {
        $mock = $this->createMock(VarArger::class);
        $mock
            ->expects($this->once())
            ->method('fn')
            ->withAnyParameters()
            ->willReturnCallback(fn ($foo, ...$args) => [$foo, ...$args]);

        $args = ['foo', 'bar', 'baz' => 'qux'];

        $this->assertSame(
            $args,
            $mock->fn(...$args),
        );
    }
}

The mock class looks like this:

<?php

class Mock_VarArger_343a613f extends Tests\Support\VarArger implements PHPUnit\Framework\MockObject\MockObject
{
    use \PHPUnit\Framework\MockObject\Api;
    use \PHPUnit\Framework\MockObject\Method;
    use \PHPUnit\Framework\MockObject\MockedCloneMethod;

    public function fn(string $foo, mixed ...$args): mixed
    {
        $__phpunit_arguments = [$foo];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 1) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 1; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'Tests\Support\VarArger', 'fn', $__phpunit_arguments, 'mixed', $this, false
            )
        );

        return $__phpunit_result;
    }
}

Expected behavior

All arguments should be passed to the callback.

[sebastianbergmann]

Fixed by #5648.