What?

Fixes: #72810

Prevents an issue where block level presets do not work correctly when:

• Default presets are disabled
• Slug matches the default preset

Why?

Without this fix theme authors are forced to define presets only at the global level or fudge block-level preset definition slugs. This leads to a poorer end user experience.

How?

The naming and shape of these preset configs can be a bit confusing but the fix itself is rather straightforward. When merging the block level config for default presets is preferred, only falling back to the global config value if it hasn't been set.

Ensuring the correct default preset config from the block level is used prevents incorrect filtering of theme presets.

Testing Instructions

For each theme.json example config below:

1. Ensure default presets for the feature being testing is on at the global level
2. Add the block level preset config to your theme.json file
3. Confirm in the editor the expected presets are available generally and at the block level

Duotone

In the image block, only the "Dark grayscale" duotone preset should be available

{
	"version": 3,
	"appearanceTools": true,
	"settings": {
		"blocks":{
			"core/image": {
				"color": {
					"defaultDuotone": false,
					"duotone": [
						{
							"name": "Dark grayscale",
							"colors": [ "#000000", "#7f7f7f" ],
							"slug": "dark-grayscale"
						}
					]
				}
			}
		}
	}
}

Shadow

In the image block, only the "Natural" shadow preset should be available

{
	"version": 3,
	"settings": {
		"appearanceTools": true,
		"blocks":{
			"core/image": {
				"shadow": {
					"defaultPresets": false,
					"presets": [
						{
							"name": "Natural",
							"slug": "natural",
							"shadow": "6px 6px 9px rgba(0, 0, 0, 0.2)"
						}
					]
				}
			}
		}
	}
}

Font Size

In the Paragraph block, only the "Small" duotone preset should be available

{
	"version": 3,
	"settings": {
		"appearanceTools": true,
		"blocks":{
			"core/paragraph": {
				"typography": {
					"defaultFontSizes": false,
					"fontSizes": [
						{
							"name": "Small",
							"slug": "small",
							"size": "13px"
						}
					]
				}
			}
		}
	}
}

Screenshots or screencast

Before	After