Automatic return value generation leads to invalid (and superfluous) test double code generation when a stubbed method returns "*|false"

[sebastianbergmann]

@mbabker tweeted about an issue with PHPUnit 9.5, PHP 8.1, and test doubles. He posted a reproducing example here. While this example is run, the following code is generated:

declare(strict_types=1);

class Mock_PDO_485bed6b extends PDO implements PHPUnit\Framework\MockObject\MockObject
{
    use \PHPUnit\Framework\MockObject\Api;
    use \PHPUnit\Framework\MockObject\Method;
    use \PHPUnit\Framework\MockObject\MockedCloneMethod;

    public function beginTransaction(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'beginTransaction', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function commit(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'commit', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function errorCode(): ?string
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'errorCode', $__phpunit_arguments, '?string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function errorInfo(): array
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'errorInfo', $__phpunit_arguments, 'array', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function exec(string $statement): false|int
    {
        $__phpunit_arguments = [$statement];
        $__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(
                'PDO', 'exec', $__phpunit_arguments, 'false|int', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function getAttribute(int $attribute): mixed
    {
        $__phpunit_arguments = [$attribute];
        $__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(
                'PDO', 'getAttribute', $__phpunit_arguments, 'mixed', $this, false
            )
        );

        return $__phpunit_result;
    }

    public static function getAvailableDrivers(): array
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "getAvailableDrivers" cannot be invoked on mock object');
    }

    public function inTransaction(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'inTransaction', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function lastInsertId(?string $name = NULL): false|string
    {
        $__phpunit_arguments = [$name];
        $__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(
                'PDO', 'lastInsertId', $__phpunit_arguments, 'false|string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function prepare(string $query, array $options = array ()): PDOStatement|false
    {
        $__phpunit_arguments = [$query, $options];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'prepare', $__phpunit_arguments, 'PDOStatement|false', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function query(string $query, ?int $fetchMode = NULL, mixed ...$fetchModeArgs): PDOStatement|false
    {
        $__phpunit_arguments = [$query, $fetchMode];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'query', $__phpunit_arguments, 'PDOStatement|false', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function quote(string $string, int $type = 3): false|string
    {
        $__phpunit_arguments = [$string, $type];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'quote', $__phpunit_arguments, 'false|string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function rollBack(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'rollBack', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function setAttribute(int $attribute, $value): bool
    {
        $__phpunit_arguments = [$attribute, $value];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'setAttribute', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }
}

declare(strict_types=1);

class PDOStatement|false
{
}

class Mock_PDOStatement|false_8ffdc1db extends PDOStatement|false implements PHPUnit\Framework\MockObject\MockObject
{
    use \PHPUnit\Framework\MockObject\Api;
    use \PHPUnit\Framework\MockObject\Method;
    use \PHPUnit\Framework\MockObject\MockedCloneMethod;
}

PDOStatement|false and Mock_PDOStatement|false_8ffdc1db are obviously invalid class names.

[sebastianbergmann]

PHPUnit 10.0-dev correctly generates only one test double class:

declare(strict_types=1);

class Mock_PDO_35d4bc58 extends PDO implements PHPUnit\Framework\MockObject\MockObject
{
    use \PHPUnit\Framework\MockObject\Api;
    use \PHPUnit\Framework\MockObject\Method;
    use \PHPUnit\Framework\MockObject\MockedCloneMethod;

    public function beginTransaction(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'beginTransaction', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function commit(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'commit', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function errorCode(): ?string
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'errorCode', $__phpunit_arguments, '?string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function errorInfo(): array
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'errorInfo', $__phpunit_arguments, 'array', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function exec(string $statement): false|int
    {
        $__phpunit_arguments = [$statement];
        $__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(
                'PDO', 'exec', $__phpunit_arguments, 'false|int', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function getAttribute(int $attribute): mixed
    {
        $__phpunit_arguments = [$attribute];
        $__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(
                'PDO', 'getAttribute', $__phpunit_arguments, 'mixed', $this, false
            )
        );

        return $__phpunit_result;
    }

    public static function getAvailableDrivers(): array
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "getAvailableDrivers" cannot be invoked on mock object');
    }

    public function inTransaction(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'inTransaction', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function lastInsertId(?string $name = NULL): false|string
    {
        $__phpunit_arguments = [$name];
        $__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(
                'PDO', 'lastInsertId', $__phpunit_arguments, 'false|string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function prepare(string $query, array $options = array ()): PDOStatement|false
    {
        $__phpunit_arguments = [$query, $options];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'prepare', $__phpunit_arguments, 'PDOStatement|false', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function query(string $query, ?int $fetchMode = NULL, mixed ...$fetchModeArgs): PDOStatement|false
    {
        $__phpunit_arguments = [$query, $fetchMode];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'query', $__phpunit_arguments, 'PDOStatement|false', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function quote(string $string, int $type = 3): false|string
    {
        $__phpunit_arguments = [$string, $type];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'quote', $__phpunit_arguments, 'false|string', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function rollBack(): bool
    {
        $__phpunit_arguments = [];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 0) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 0; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'rollBack', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }

    public function setAttribute(int $attribute, $value): bool
    {
        $__phpunit_arguments = [$attribute, $value];
        $__phpunit_count     = func_num_args();

        if ($__phpunit_count > 2) {
            $__phpunit_arguments_tmp = func_get_args();

            for ($__phpunit_i = 2; $__phpunit_i < $__phpunit_count; $__phpunit_i++) {
                $__phpunit_arguments[] = $__phpunit_arguments_tmp[$__phpunit_i];
            }
        }

        $__phpunit_result = $this->__phpunit_getInvocationHandler()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation(
                'PDO', 'setAttribute', $__phpunit_arguments, 'bool', $this, false
            )
        );

        return $__phpunit_result;
    }
}

The default return value generator correctly returns false for PDOStatement|false and does not try to generate code for a stub for PDOStatement|false.