TypeError if #[ReOrderHook] targets hook that has no implementations anywhere in enabled modules. [#3536470]

Problem/Motivation

In HookCollectorPass when we apply order operations, we are not checking if that hook is actually implemented.

This scenario is valid because the attribute might target a hook implementation in another module that may or may not be installed, or where that hook implementation only exists in specific versions of that module.

Steps to reproduce

(The examples are for #[ReorderHook] only. Currently #[RemoveHook] does not cause this kind of problems, but we should include it in the tests.)

Problem scenario 1: Trivial example

A #[ReorderHook] targets a non-existing method.
The hook has no implementations.

#[ReorderHook('non_implemented_hook', 'NonExistingClass', 'nonExistingMethod', Order::Last)]
#[ReorderHook('non_implemented_type_alter', 'NonExistingClass', 'nonExistingMethod', Order::Last)]
class MyHooks {...}

Expected: The attributes are ignored.
Actual: The #[ReorderHook] attributes cause problems during rebuild:

TypeError: Drupal\Core\Hook\HookCollectorPass::applyOrderOperations(): Argument #1 ($implementation_list) must be of type array, null given, called in /var/www/html/core/lib/Drupal/Core/Hook/HookCollectorPass.php on line 255

Problem scenario 2: Advanced case

A #[ReorderHook] targets an existing method, which may implement a different hook.
The actual target hook has no implementations.

#[ReorderHook('form_myform_alter', self::class, 'formAlter2', Order::First)]
class MyHooks {
  #[Hook('form_alter')]
  public function formAlter1(array &$form): void {
    $form['#alter_calls'][] = __METHOD__;
  }
  #[Hook('form_alter')]
  public function formAlter2(array &$form): void {
    $form['#alter_calls'][] = __METHOD__;
  }
}

Expected: The attributes are ignored.
Actual behavior: Error during rebuild, as above.

Working example 1: Reorder a non-existing method

A #[ReorderHook] targets a non-existing method.
The hook has at least one implementation.

// Target non-existing methods for reordering.
#[ReorderHook('regular_hook', 'NonExistingClass', 'nonExistingMethod', Order::Last)]
#[ReorderHook('regular_type_alter', 'NonExistingClass', 'nonExistingMethod', Order::Last)]
class MyHooks {
  // Make sure the hooks have at least one implementation.
  #[Hook('regular_hook')]
  public function regularHook(): void {}
  #[Hook('regular_type_alter')]
  public function regularTypeAlter(): void {}
}

Expected = Actual: The #[ReorderHook] attributes have no effect.

Working example 2: Reordering across alter hooks

A #[ReorderHook] targets an existing method from a different hook.
The hook has at least one implementation.

#[ReorderHook('form_myform_alter', self::class, 'formAlter2', Order::First)]
class MyHooks {
  #[Hook('form_alter')]
  public function formAlter1(array &$form): void {}
  #[Hook('form_alter')]
  public function formAlter2(array &$form): void {}
}
class OtherModuleHooks {
  #[Hook('form_myform_alter')]
  public function formMyformAlter(array &$form): void {}
}

Expected: The attributes are ignored.
Actual behavior:

For `->alter('form', ..)`, the #[ReorderHook] attribute has no effect.
The call order is [MyHooks::formAlter1, MyHooks::formAlter2].
For `->alter(['form', 'form_myform'], ..)`, the #[ReorderHook] attribute causes the formAlter2 method to run first.
The call order is [MyHooks::formAlter2, OtherModuleHooks::formMyformAlter, MyHooks::formAlter1] (also depending on module order).

The reason:
- In HookCollectorPass::applyOrderOperations(), the order operation has no effect, but it is still stored as argument for ModuleHandler.
- In ModuleHandler::getCombinedListeners() for a combination of alter hooks, the order operation does have an effect.

Proposed resolution

https://git.drupalcode.org/project/drupal/-/merge_requests/12858
(changed) Discard ordering directives if the target method is not registered for the target hook specified in the #[ReorderHook] attribute.
(also discard the ordering directive if the target method is missing, or was removed with #[RemoveHook]).
(changed) In combined alter calls, ordering directives can no longer reorder implementations from other hooks.

Effect:

Problem scenario 1: (changed) The #[ReorderHook] has no effect. No error during rebuild.
Problem scenario 2: (changed) The #[ReorderHook] has no effect. No error during rebuild.
Working scenario 1: (unchanged) The #[ReorderHook] has no effect.
Working scenario 2: (changed) The #[ReorderHook] has no effect.

Remaining tasks

Review

User interface changes

N/A

Introduced terminology

N/A

API changes

[#ReorderHook] must match all aspects for it to take effect and must target an existing implementation. Otherwise it is dropped from the ordering ruleset.

Data model changes

N/A

Release notes snippet

N/A

Comment	File	Size	Author
#36	3536470-nr-bot_20czpw5l.txt	6.73 KB	needs-review-queue-bot

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