A nested/recursive pluck()

[msacharewicz]

The Collection lacks a method to pluck values recursively.

There are many scenarios, in which we operate on Collection-stored trees. Such trees contain a recursively-nested nodes, with same properties each, for example:

[
    "User" => [
        "class" => "App\Models\User",
        "inheritsFrom" => [
            "Role" => [
                "class" => "App\Models\Role",
                "inheritsFrom" => [],
            ],
            "Group" => [
                "class" => "App\Models\Group",
                "inheritsFrom" => [
                    "Role" => [
                        "class" => "App\Models\Role",
                        "inheritsFrom" => [],
                    ],
                ],
            ],
        ],
    ],
],

Currently, there is no method on Collection to simply pluck all values of the same key from the entire collection.

Consider following macro implementation to better understand the feature:

Collection::macro('pluckRecursive', function ($key) {
    $values = collect();
    $this->each(function ($item) use ($key, &$values) {
        if (is_array($item) && array_key_exists($key, $item)) {
            $values->push($item[$key]);
        }
        if (is_array($item)) {
            $values = $values->concat(collect($item)->pluckRecursive($key));
        }
    });
    return $values;
});

Usage:

$tree->pluckRecursive("class");

Result:

[
  "App\Models\User",
  "App\Models\Role",
  "App\Models\Group",
  "App\Models\Role",
],

(we do not need uniqueness, we have unique() for that)

While macros are a fine workaround, they bring their own issues. Would it be possible to implement such function in the core?