Style hooks - default values cause extra wrappers and block errors in editor for standard blocks.

[Addison-Stavlo]

Describe the bug
Semi-related to #24363.

Style hooks seem to be written with the intent to support default styles to be defined on the block- ex:

gutenberg/packages/block-editor/src/hooks/color.js

Lines 70 to 76 in 65258a0

	// allow blocks to specify their own attribute definition with default values if needed.
	if ( ! settings.attributes.backgroundColor ) {
	Object.assign( settings.attributes, {
	backgroundColor: {
	type: 'string',
	},
	} );

However, in practice this seems to not play nice in the editor. With standard blocks (reproduced with Paragraph and Heading), default styles add extra wrappers in the editor and can break the blocks.

To reproduce

Below I will explore this with a standard block, "Paragraph".

1. Add the following to attributes in Paragraph's block.json file:

		"textColor": {
			"type": "string",
			"default": "secondary"
		},
		"backgroundColor": {
			"type": "string",
			"default": "primary"
		},
		"fontSize": {
			"type": "string",
			"default": "large"
		}

2. Load the editor and add/edit a new paragraph. It should have the default values as expected:
   

3. Select custom values for the fontSize, backgroundColor, and textColor and save:
   

4. Reload the editor, notice the block has a different size and indentation:
   

Inspecting the element reveals that there is a <p> element nested inside the Paragraph wrapper:

5. Try changing to a different custom background color for the block. Notice the background is only applied to outer wrapper:
   

6. Save and reload the editor, you may find the block has broken:
   

Expected behavior
Expected to not have a second wrapper and broken block.

[Addison-Stavlo]

FYI @youknowriad (not to be confused with #24363)

[youknowriad]

This only applies to paragraphs right?

To support p-less paragraph blocks we have a "deprecated" version for the paragraph block used to auto-add the p wrapper. I think that's probably what's causing the double paragraphs here. I saw in the past that this deprecated version of paragraph block caused other similar issues (double p), so I wonder if we can rework it and try to apply it only when we detect p-less paragraphs.

[Addison-Stavlo]

This only applies to paragraphs right?

It seems to be the case with the heading block as well. I haven't tested beyond those two currently.

[youknowriad]

It seems to be the case with the heading block as well. I haven't tested beyond those two currently.

In that case, it's a different story independent with the "p -less" deprecation.

[annezazu]

Just an FYI that I did the best I could to label this but if others have a better possible label, please update!