Used attribute itemsJustification is not declared in block's schema

[ntsekouras]

Is there an existing issue for this?

• I have searched the existing issues

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• I have tested with all plugins deactivated.

Have you tried replicating the bug using a default theme e.g. Twenty Twenty?

• I have tested with a default theme.

Description

In #28980 items justification was added to Social Links block. This PR though while started using a new attribute(itemsJustification) it was never declared in the block's schema(block.json).

Step-by-step reproduction instructions

1. Insert a Social Links block and change the justification from the control.
2. Save and reload
3. Change again the value and observe that has both conflicting classes

Also check the blocks block.json file.

Expected Behavior

The attribute should be declared and a migration would be needed based on existing classes.

I would propose though to hold onto this a bit before fixing, as in this PR: #33987 there is exploration of using a flex layout for this block. If this PR lands we would need to remove the now missing attribute, so this issue will be resolved.

Current Behavior

What this means in practice is that the attribute is never saved. When we insert such a block the value is undefined so the default behavior felt okay (left align/flex-start). While editing this value by the corresponding control we were setting the value with setAttributes, which doesn't sanitize the attributes, and added a css class which was was then saved. On reload though, the same block seemed to be keeping its behavior by the css classname and not the attribute - the attribute is undefined. So if you change this value after reload a new css class will be applied that leads to multiple conflicting classes - there is only one winner though with unexpected results 😄 .