Issue with dynamically created callback method

[schlessera]

BrainMonkey does not seem to correctly identify dynamically created callback methods.

I created a new callback method to be used as an add_filter() callback:

class MyClass() {

    public function register( $arg ) {
        $method_name = "callback_for_${arg}";

        $this->$method_name = function ( $value ) use ( $arg ) {
            return $value;
        }

        add_filter( 'my_filter', [ $this, $method_name ] );
    }
}

This code will cause BrainMonkey to throw an InvalidArgumentException:

InvalidArgumentException: A callback is required to add a filter.

When I var_dump the state inside of the Brain\Monkey\WP\Hooks::args() method, I get the following:

array(5) {
  'args' =>
  array(0) {
  }
  'type' =>
  string(6) "filter"
  'getId' =>
  bool(false)
  'hook' =>
  string(21) "my_filter"
  'callback' =>
  array(2) {
    [0] =>
    class MyClass#29 (2) {
      public $callback_for_test =>
      class Closure#50 (3) {
        ...
      }
    }
    [1] =>
    string(17) "callback_for_test"
  }
}

[schlessera]

The dump I did was this:

private function args(array $args, $type, $getId = false) {
    // [...]
    if (($getId && ! is_string($callback)) || (! $getId && ! is_callable($callback))) {
        var_dump( [
            'args' => $args,
            'type' => $type,
            'getId' => $getId,
            'hook' => $hook,
            'callback' => $callback
        ] );
        //throw new InvalidArgumentException("A callback is required to add a {$type}.");
    }
    // [...]
}

[gmazzap]

According to your code, the callback added to the filter is [ $this, $method_name ], but that's not a valid callback: a valid callback can take the form of an array only if the first array element is an object (class name or instance), and the second element is a method name in a string.

In your code, $method_name is actually a Closure...

This is the proof of I want to say: https://3v4l.org/6Au6U

Is there something wrong in the code you posted as example here?

For example, if you change the code to:

add_filter( 'my_filter', $this->$method_name );

it works, see here: https://3v4l.org/5MgOi

[schlessera]

Hmm, I'll have to investigate some more. I know that it is a Closure, but I'm using this exact code in another place as well, without unit tests, and it just works with WP filters...

I'll keep you updated.

[schlessera]

Okay, nevermind, I'm just too stupid to read my own code...

In the other class, I did indeed add the closure in the exact same way, but WordPress filtering did not work as is, but only because I had also added the following piece of code to that class as well:

    /**
     * Magic method to allow dynamic callbacks
     *
     * @throws BadMethodCallException An undefined callback was invoked.
     *
     * @since 1.0.0
     *
     * @param  string $method         Method that has been called.
     * @param  array  $args           Arguments that have been passed to the
     *                                method.
     * @return mixed                  Return value of the method being called.
     */
    public function __call( $method, $args ) {
        if ( is_callable( array( $this, $method ) ) ) {
            return call_user_func_array( $this->$method, $args );
        }
        throw new BadMethodCallException( 'An undefined callback was invoked: ' . (string) $method );
    }

As soon as I add this magic method, the tests with BrainMonkey work as well.

So, please just ignore my nonsense above! :)

[gmazzap]

@schlessera Things like this just happen: this is why we write unit tests. I'm just happy that BrainMonkey did its work: catched an error during unit tests ;)