Fix/theme json schema validation

[t-hamano]

Fix: #44442

What?

This PR solves the problem that the three properties filter, shadow, and outline are not defined correctly in the theme.json schema.

Why?

This is because these three are not correctly defined in the properties section that is the source of the validation.

How?

I updated filter, shadow, and outline in a consistent order, besides adding the definitions.

Testing Instructions

• Create the following JSON file with all three properties defined in all locations.

theme.json

{
	"$schema": "https://schemas.wp.org/trunk/theme.json",
	"version": 2,
	"styles": {
		"filter": {},
		"shadow": "",
		"outline": {},
		"elements": {
			"button": {
				"filter": {},
				"shadow": "",
				"outline": {},
				":active": {
					"filter": {},
					"shadow": "",
					"outline": {}
				},
				":focus": {
					"filter": {},
					"shadow": "",
					"outline": {}
				},
				":hover": {
					"filter": {},
					"shadow": "",
					"outline": {}
				}
			}
		},
		"blocks": {
			"core/button": {
				"filter": {},
				"shadow": "",
				"outline": {}
			},
			"core/heading": {
				"filter": {},
				"shadow": "",
				"outline": {}
			}
		}
	}
}

• Confirm that the code editor shows errors in some properties.

• Change the schema reference to this PR.

{
	"$schema": "https://raw.githubusercontent.com/WordPress/gutenberg/fix/theme-json-schema-validation/schemas/json/theme.json"
}

• Confirm that all error messages disappear. At the same time, verify that these three properties don't appear as automatic candidates outside of the allowed locations.

[ajlende]

Looks good! Thanks for all the JSON Schema fixes!

[ajlende]

*sigh* I wish there was a better way in JSON schema draft-04 to add properties than updating 5 different places in a nearly 2000 line file, but unless we start generating the schema from our own metadata, we'll just have to keep fixing issues like these.

[t-hamano]

Thank you for the review!
For example, if we only consider what is required of a JSON schema (validation and autocompletion), we should easily be able to define the following:

"stylesPropertiesComplete": {
	"type": "object",
	"allOf": [
		{
			"$ref": "#/definitions/stylesProperties"
		},
		{
			"properties": {
				"border": {},
				"color": {},
				"spacing": {},
				"typography": {},
				"filter": {},
				"shadow": {},
				"outline": {}
			},
			"additionalProperties": false
		}
	]
},

to...

```json
"stylesPropertiesComplete": {
	"type": "object",
	"allOf": [
		{
			"$ref": "#/definitions/stylesProperties"
		},
		{
			"additionalProperties": false
		}
	]
},

But since the current implementation of the document generator only takes properties into account, I think there is always a need to do a double definition.

I wish I could update the logic to generate the appropriate documentation, taking into account ref 😅

[ajlende]

Unfortunately the second one doesn't work as JSON schema validates the sub-schemas in allOf independently. It would validate the types of all of the stylesProperties which would pass, and then it would validate { "additionalProperties": false } which says that there should be no properties which would always fail.

It's a limitation of JSON schema in general, and it's one of the reasons some projects, like the tsconfig JSON schema, genreate the schema from metadata instead of writing it by hand.

EDIT: I should have been more specific in my initial comment rather than just complaining. And this isn't to say that we should do our schema exactly like TypeScript—we have our own unique project constraints. All I know is that as long as we're writing the schema by hand, we're going to keep running into issues like this. I don't have the capacity to work on such a system right now, but it's on my wish list. Until then, I appreciate the fixes you've been making 🙂

[t-hamano]

Thank you for the detailed explanation. If there is anything I can do, I will assist you 👍