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re-unite meta-schema #1610

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cd0d4bf
re-unite meta-schema
gregsdennis Jun 22, 2025
44c5c0e
allow for x- properties
gregsdennis Jun 22, 2025
33d7241
disallow other $* keywrods
gregsdennis Jun 22, 2025
154b863
disallow other $* keywords (fix)
gregsdennis Jun 22, 2025
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63 changes: 0 additions & 63 deletions specs/meta/applicator.json
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14 changes: 0 additions & 14 deletions specs/meta/content.json
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48 changes: 0 additions & 48 deletions specs/meta/core.json
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11 changes: 0 additions & 11 deletions specs/meta/format-annotation.json
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11 changes: 0 additions & 11 deletions specs/meta/format-assertion.json
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34 changes: 0 additions & 34 deletions specs/meta/meta-data.json
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191 changes: 191 additions & 0 deletions specs/meta/meta.json
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{
"$schema": "https://json-schema.org/version/year/meta",
"$id": "https://json-schema.org/version/year/meta",
Comment on lines +2 to +3
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What's "meta"? (Sorry if it's something we discussed and I forgot.)

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Also, what's the reason for using a placeholder for "version" and "year"?

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What's "meta"?

it was late. It should just be /version/year

Also, what's the reason for using a placeholder for "version" and "year"?

It's not published yet. Just wanted to communicate the idea.

"$dynamicAnchor": "meta",

"title": "JSON Schema Core and Validation specification meta-schema",
"type": ["object", "boolean"],
"properties": {
"$id": {
"$ref": "#/$defs/iriReferenceString",
"$comment": "Fragments not allowed.",
"pattern": "^[^#]*$"
},
"$schema": { "$ref": "#/$defs/iriString" },
"$ref": { "$ref": "#/$defs/iriReferenceString" },
"$anchor": { "$ref": "#/$defs/anchorString" },
"$dynamicRef": { "$ref": "#/$defs/iriReferenceString" },
"$dynamicAnchor": { "$ref": "#/$defs/anchorString" },
"$comment": {
"type": "string"
},
"$defs": {
"type": "object",
"additionalProperties": { "$dynamicRef": "#meta" }
},
"title": {
"type": "string"
},
"description": {
"type": "string"
},
"default": true,
"deprecated": {
"type": "boolean",
"default": false
},
"readOnly": {
"type": "boolean",
"default": false
},
"writeOnly": {
"type": "boolean",
"default": false
},
"examples": {
"type": "array",
"items": true
},
"prefixItems": { "$ref": "#/$defs/schemaArray" },
"items": { "$dynamicRef": "#meta" },
"maxContains": { "$ref": "#/$defs/nonNegativeInteger" },
"minContains": {
"$ref": "#/$defs/nonNegativeInteger",
"default": 1
},
"contains": { "$dynamicRef": "#meta" },
"additionalProperties": { "$dynamicRef": "#meta" },
"properties": {
"type": "object",
"additionalProperties": { "$dynamicRef": "#meta" },
"default": {}
},
"patternProperties": {
"type": "object",
"additionalProperties": { "$dynamicRef": "#meta" },
"propertyNames": { "format": "regex" },
"default": {}
},
"dependentSchemas": {
"type": "object",
"additionalProperties": { "$dynamicRef": "#meta" },
"default": {}
},
"propertyNames": { "$dynamicRef": "#meta" },
"if": { "$dynamicRef": "#meta" },
"then": { "$dynamicRef": "#meta" },
"else": { "$dynamicRef": "#meta" },
"allOf": { "$ref": "#/$defs/schemaArray" },
"anyOf": { "$ref": "#/$defs/schemaArray" },
"oneOf": { "$ref": "#/$defs/schemaArray" },
"not": { "$dynamicRef": "#meta" },
"unevaluatedItems": { "$dynamicRef": "#meta" },
"unevaluatedProperties": { "$dynamicRef": "#meta" },
"type": {
"anyOf": [
{ "$ref": "#/$defs/simpleTypes" },
{
"type": "array",
"items": { "$ref": "#/$defs/simpleTypes" },
"minItems": 1,
"uniqueItems": true
}
]
},
"const": true,
"enum": {
"type": "array",
"items": true
},
"multipleOf": {
"type": "number",
"exclusiveMinimum": 0
},
"maximum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"minimum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"maxLength": { "$ref": "#/$defs/nonNegativeInteger" },
"minLength": { "$ref": "#/$defs/nonNegativeIntegerDefault0" },
"pattern": {
"type": "string",
"format": "regex"
},
"maxItems": { "$ref": "#/$defs/nonNegativeInteger" },
"minItems": { "$ref": "#/$defs/nonNegativeIntegerDefault0" },
"uniqueItems": {
"type": "boolean",
"default": false
},
"maxProperties": { "$ref": "#/$defs/nonNegativeInteger" },
"minProperties": { "$ref": "#/$defs/nonNegativeIntegerDefault0" },
"required": { "$ref": "#/$defs/stringArray" },
"dependentRequired": {
"type": "object",
"additionalProperties": {
"$ref": "#/$defs/stringArray"
}
},
"format": { "type": "string" },
"contentEncoding": { "type": "string" },
"contentMediaType": { "type": "string" },
"contentSchema": { "$dynamicRef": "#meta" },

"$vocabulary": {
"$comment": "Proposed keyword: https://github.com/json-schema-org/json-schema-spec/blob/main/specs/proposals/vocabularies.md"
},
"propertyDependencies": {
"$comment": "Proposed keyword: https://github.com/json-schema-org/json-schema-spec/blob/main/specs/proposals/propertyDependencies.md"
}
},
"patternProperties": {
"^x-": true,
"^(?!(?:\\$id|\\$schema|\\$ref|\\$anchor|\\$dynamicRef|\\$dynamicAnchor|\\$comment|\\$defs)$)\\$.*": false
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Isn't this superfluous?

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Karen suggested an improvement.

It's needed. The updated spec restricts the definition of custom $* keywords. The only way to do that is to explicitly allow the ones you have.

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I think the meta-schema should adhere to jsonschema-core's "given the high disparity in regular expression constructs support, schema authors SHOULD limit themselves to the following regular expression tokens: ...".
Negative lookahead is definitely a feature with much disparity in support.
But I don't know another way to express this constraint for patternProperties.
Maybe propertyNames would be better suited to validate this?

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@gregsdennis gregsdennis Jun 27, 2025 •
edited
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good catch. Maybe this is one of those requirements where we just don't enforce it with the meta-schema. I'm okay with that.

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I don't know another way to express this constraint for patternProperties.

Would you be willing to do it with additionalProperties?

Suggested change
"^(?!(?:\\$id|\\$schema|\\$ref|\\$anchor|\\$dynamicRef|\\$dynamicAnchor|\\$comment|\\$defs)$)\\$.*": false
"^([^$].*)?$": true
},
"additionalProperties": false,

"^([^$].*)?$": true in patternProperties allows property names that are either the empty string or start with a character other than $, making "additionalProperties": false apply exclusively to (and reject) properties that lack an explicit mention in properties and start with $.

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@gibson042 Thanks for the clever suggestion, but that solution doesn't work well with extensions and unevaluatedProperties. An over simplified example of extending the meta-schema might look like this,

{
  "$ref": "https://json-schema.org/1/2025",
  "properties": {
    "foo": { "type": "number" },
    "$foo": { "type": "number" }
  },
  "unevaluatedProperties": false
}

unevaluatedProperties is included to get errors when someone uses an undefined keyword in their schema. But, additionalProperties effectively makes all properties considered evaluated and unevaluatedProperties can't do what we want it to do.

We can get around this problem by using double negation to drop annotations,

    "not": {
      "not": {
        "patternProperties": {
          "^[^$]|^\\$(id|schema|ref|anchor|dynamicRef|dynamicAnchor|comment|defs)$": true
        },
        "additionalProperties": false
      }
    },

But, error messaging with not is so unhelpful, I think it's better to just leave it out.

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@jdesrosiers jdesrosiers Jun 30, 2025 •
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Maybe propertyNames would be better suited to validate this?

I think this would work,

    "propertyNames": {
      "pattern": "^[^$]|^\\$(id|schema|ref|anchor|dynamicRef|dynamicAnchor|comment|defs)$"
    },

It doesn't interfere with unevaluatedProperties and the error messaging is reasonable.

},
"$defs": {
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This appears to be missing a definition for "stringArray".

"anchorString": {
"type": "string",
"pattern": "^[A-Za-z_][-A-Za-z0-9._]*$"
},
"iriString": {
"type": "string",
"format": "iri"
},
"iriReferenceString": {
"type": "string",
"format": "iri-reference"
},
"nonNegativeInteger": {
"type": "integer",
"minimum": 0
},
"nonNegativeIntegerDefault0": {
"$ref": "#/$defs/nonNegativeInteger",
"default": 0
},
"schemaArray": {
"type": "array",
"minItems": 1,
"items": { "$dynamicRef": "#meta" }
},
"simpleTypes": {
"enum": [
"array",
"boolean",
"integer",
"null",
"number",
"object",
"string"
]
}
}
}
12 changes: 0 additions & 12 deletions specs/meta/unevaluated.json
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