Instance::moveToSlot() error when an ancestor is a not a SDC

We may need to merge #3573805: Empty renderables in regions prevent layouts rendering before completing this work

#3573805: Empty renderables in regions prevent layouts rendering is merged.

I can resume my work. Not ready for merge yet: it seems the bug is fixed, we are also now totally SDC agnostic; and we have a bunch of kernel tests to check this, but it is at the cost of this mechanism:

    // To avoid non consecutive array keys, we rebuild the value list.
    $slot_path = \array_slice($path, 0, \count($path) - 1);
    $slot = NestedArray::getValue($root, $slot_path);
    NestedArray::setValue($root, $slot_path, \array_values($slot));

This may have unfortunate side effects. Let's see if the playwright tests are OK

Hello Jean,

Here are the challenges of the work done here, once we moved from hardcoded SDC logic to SourceWithSlotInterface.

InstanceSlotOperationsTest and array list indexation

If we have this structure:

• a slot with 2 sources:
  • the source "A" to move, indexed "0"
  • a source "B" with slots (ComponentSource, LayoutSource...), indexed "1"

If we Instance::moveToSlot() the source "A" into a slot of "B" we have this unexpected structure:

[sources] 
  [0] 
    [node_id] => B
    [source_id] => layout
    [source] 
      [plugin_id] => layout_onecol
      [regions] 
            [content] 
  [1] 
    [source] 
      [regions] 
        [content] 
          [0] 
            [node_id] => A
            [source_id] => textfield

Where the source property with the new value is dissociated from the node_id, the source_id and the original source.

Let's take a Instance::moveToSlot() action, it is divided in 2 internal steps:

1. Instance::doRemove() is reindexing the "B" (from "1" to "0") after the removal of "A":
   

       // To avoid non consecutive array keys, we rebuild the value list.
       $slot_path = \array_slice($path, 0, \count($path) - 1);
       $slot = NestedArray::getValue($root, $slot_path);
       NestedArray::setValue($root, $slot_path, \array_values($slot));

2. Instance::doAttachToSlot() is still believing "B" is indexed at "1" and merging the array structure teh wrong way

So, in the MR, we moved the reindexing of list indexes (\array_values($slot));) from ::doRemove() to the beginning of ::buildIndexFromSlot() and now we have a food source structure but badly indexed ("1" instead of "0"):

[sources] 
  [0] 
  [1] 
    [node_id] => B
    [source_id] => layout
    [source] 
      [plugin_id] => layout_onecol
      [regions] 
        [content] 
          [0] 
            [node_id] => A
            [source_id] => textfield

So, in InstanceSlotOperationsTest::testMoveFromComponentToNestedLayoutEmptyRegion) test, we considered this OK because we want to keep consistent indexes during the chain of atomic operation and we expect the values to be correctly indexed at the very end, thanks to ::buildIndexFromSlot().

I hope it was the right bet.

Some change in InstanceHistoryTest

For your information.