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Example of $recursiveRoot and $recursiveRef #605

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Example of $recursiveRoot and $recursiveRef #605

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18a9d19
Example of $recursiveRoot and $recursiveRef
handrews Jun 15, 2018
4c0599e
schema.json does not need recursiveRoot
handrews Jun 15, 2018
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33 changes: 33 additions & 0 deletions hyper-operations.json
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@@ -0,0 +1,33 @@
{
"$schema": "http://json-schema.org/draft-08/hyper-operations-FAKE#",
"$id": "http://json-schema.org/draft-08/hyper-operations-FAKE",
"$recursiveRoot": true,
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This schema extends another recursive schema, and in this PR example, nothing extends it. So it is always the entry point schema when it is used at all.

So here "$recursiveRoot": true pins the target of all "$recursiveRef"s that are encountered.


"title": "FAKE DEMO JSON Hypermedia Operations FOR RECURSION EXAMPLE",
"$ref": "http://json-schema.org/draft-08/hyper-schema",
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This is a regular "$ref", as a "$recursiveRef" here would loop back to this root schema and be an infinite loop. A normal "$ref" is used for the extension reference.

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@gregsdennis gregsdennis Jun 15, 2018 •
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Did we resolve the issue of $ref having sibling keywords? (Otherwise, how does this work?)

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Looks like there's an informal decision in #523. I guess you're assuming that?

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Yes, there's also PR #585 which will hopefully start moving again soon. I've been acting as if it's done because that's definitely what draft-08 will look like. (I'm not sure what you mean by "informal decision", do we even have formal decisions here? Other than merging PRs?)

"properties": {
"base": {
"type": "string",
"format": "uri-template"
},
"links": {
"items": {
"operations": {
"type": "array",
"items": {
"type": "object",
"properties": {
"someKindOfSchema": { "$recursiveRef": "#" }
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This "$recursiveRef" is controlled by the "$recursiveRoot": true above, but since (in our example here in the PR), this is a meta-schema that extends others but is never extended, the default target of "#" and the recursive root are the same.

}
}
}
}
}
},
"links": [
{
"rel": "self",
"href": "{+%24id}"
}
]
}
57 changes: 5 additions & 52 deletions hyper-schema.json
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@@ -1,66 +1,19 @@
{
"$schema": "http://json-schema.org/draft-08/hyper-schema#",
"$id": "http://json-schema.org/draft-08/hyper-schema#",
"$id": "http://json-schema.org/draft-08/hyper-schema",
"$recursiveRoot": true,
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Hyper-schema is a recursive meta-schema. It extends the core/validation recursive meta-schema, and is in turn extended by the hyper-operations meta-schema (which is fake and made up for this example). It also references links.json, which is the stand-alone LDO schema, which refers back to this meta-schema.

If hyper-schema.json is the entry point schema document, then this "$recursiveRot": true sets the "$recursiveRef" target for all processing. However, if hyper-operations.json is the entry point, then this "$recursiveRoot" is ignored because hyper-operations.json already set it, and we only arrive at this meta-schema through hyper-operations.json.

A more complex example is if links.json is the entry point schema. That is not a recursive schema, so it does not set "$recursiveRoot". However, it does "$recursiveRef" this meta-schema. When such a "$recursiveRef" (or "$ref") is followed from a non-recursive schema, then this "$recursiveRoot" is the first one seen, and sets the target for all further "$recursiveRef"s.


"title": "JSON Hyper-Schema",
"$defs": {
"schemaArray": {
"allOf": [
{ "$ref": "http://json-schema.org/draft-08/schema#/$defs/schemaArray" },
{
"items": { "$ref": "#" }
}
]
}
},
"allOf": [ { "$ref": "http://json-schema.org/draft-08/schema#" } ],
"$ref": "http://json-schema.org/draft-08/schema",
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As with hyper-operations.json referencing this schema, we use "$ref" to extend the regular core/validation schema.

"properties": {
"additionalItems": { "$ref": "#" },
"additionalProperties": { "$ref": "#"},
"dependencies": {
"additionalProperties": {
"anyOf": [
{ "$ref": "#" },
{ "type": "array" }
]
}
},
"items": {
"anyOf": [
{ "$ref": "#" },
{ "$ref": "#/$defs/schemaArray" }
]
},
"$defs": {
"additionalProperties": { "$ref": "#" }
},
"definitions": {
"$comment": "Renamed to $defs, but retained here to ensure compatibility",
"additionalProperties": { "$ref": "#" }
},
"patternProperties": {
"additionalProperties": { "$ref": "#" }
},
"properties": {
"additionalProperties": { "$ref": "#" }
},
"if": {"$ref": "#"},
"then": {"$ref": "#"},
"else": {"$ref": "#"},
"allOf": { "$ref": "#/$defs/schemaArray" },
"anyOf": { "$ref": "#/$defs/schemaArray" },
"oneOf": { "$ref": "#/$defs/schemaArray" },
"not": { "$ref": "#" },
"contains": { "$ref": "#" },
"propertyNames": { "$ref": "#" },

"base": {
"type": "string",
"format": "uri-template"
},
"links": {
"type": "array",
"items": {
"$ref": "http://json-schema.org/draft-08/links#"
"$ref": "http://json-schema.org/draft-08/links"
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The reference to links.json is a regular "$ref" as it is not a recursive reference to start with.

However, since at this point we have already set "$recursiveRoot": true (either here or from hyper-operations.json), when we see "$recursiveRef" inside of links.json from here, those "$recursiveRef"s have their targets changed to point to the appropriate "$recursive Root".

}
}
},
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10 changes: 5 additions & 5 deletions links.json
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@@ -1,6 +1,6 @@
{
"$schema": "http://json-schema.org/draft-08/hyper-schema#",
"$id": "http://json-schema.org/draft-08/links#",
"$id": "http://json-schema.org/draft-08/links",
"title": "Link Description Object",
"allOf": [
{ "required": [ "rel", "href" ] },
Expand Down Expand Up @@ -29,7 +29,7 @@
"format": "uri-template"
},
"hrefSchema": {
"$ref": "http://json-schema.org/draft-08/hyper-schema#"
"$recursiveRef": "http://json-schema.org/draft-08/hyper-schema"
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When using links.json as a standalone schema, it is the entry point schema, and for the initial evaluation it does not matter whether this is a "$ref" or a "$recursiveRef". This schema does not set "$recursiveRoot", so the literal URI reference value provided here is used as-is.

When links.json is referenced from hyper-schema.json (with hyper-schema.json as the entry point), then we have seen as "$recursiveRoot", so the literal value is ignored and the target is the root schema of hyper-schema.json

When links.json is referenced from hyper-schema.json, when the entry point was hyper-operations.json, then the "$recusiveRoot" in hyper-operations.json is the first encountered, so the target of this (and other) "$recursiveRef"s is the root schema of hyper-operations.json

These behaviors show how the same links.json can be used on its own (referring to hyper-schema.json which extends schema.json) and as a component within hyper-schema.json (or an extension of it, such as hyper-operations.json).

},
"templatePointers": {
"type": "object",
Expand All @@ -55,21 +55,21 @@
"type": "string"
},
"targetSchema": {
"$ref": "http://json-schema.org/draft-08/hyper-schema#"
"$recursiveRef": "http://json-schema.org/draft-08/hyper-schema"
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@handrews handrews Jun 15, 2018 •
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Since there is no "$recursiveRoot" in links.json when used as an entry point, each time we reference a document with a "$recursiveRoot", the root is set just for that reference and any further references it makes. Then when we move "out" of this "$recursiveReference" and on to the next one for some other LDO property, the process repeats.

This still works fine when we start from links.json, "$recursiveRef" into hyper-schema, and then reference back to links.json again. The sequence is:

  • Enter links.json (no "$recursiveRoot")
  • "$recursiveRef" to hyper-schema (use the URI reference directly as there's no root yet)
    • Enter hyper-schema.json, see "$recursiveRoot" for the first time, set the recursion target
    • "$ref" to schema.json (extending the core/validation meta-schema)
      • Enter schema.json, which does not need "$recursiveRoot" (see 2nd review, I changed this from the initial version)
      • Any "$recursiveRef"s encountered, such as for the applicator keywords, go to the recursion target, which is hyper-schema.json
    • Back out in hyper-schema.json, "$ref" to links (this is never recursive)
      • Re-enter links.json, the recursive root is still set from hyper-schema.json
      • Encounter a "$recursiveRef" to hyper-schema, but now with the recursion target set use that (in this case, it happens to point to the same place)
      • This continues as we walk over the instance and bounce back and forth between links.json, hyper-schema.json, and schema.json

},
"targetMediaType": {
"type": "string"
},
"targetHints": { },
"headerSchema": {
"$ref": "http://json-schema.org/draft-08/hyper-schema#"
"$recursiveRef": "http://json-schema.org/draft-08/hyper-schema"
},
"submissionMediaType": {
"type": "string",
"default": "application/json"
},
"submissionSchema": {
"$ref": "http://json-schema.org/draft-08/hyper-schema#"
"$recursiveRef": "http://json-schema.org/draft-08/hyper-schema"
},
"$comment": {
"type": "string"
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42 changes: 24 additions & 18 deletions schema.json
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@@ -1,12 +1,13 @@
{
"$schema": "http://json-schema.org/draft-08/schema#",
"$id": "http://json-schema.org/draft-08/schema#",

"title": "Core schema meta-schema",
"$defs": {
"schemaArray": {
"type": "array",
"minItems": 1,
"items": { "$ref": "#" }
"items": { "$recursiveRef": "#" }
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schema.json does not need "$recursiveRoot": true, as it is not extending anything. So using the literal URI reference of # in "$recursiveRef": "#" produces the correct behavior when using schema.json directly.

When used from hyper-schema.json (with either it, links.json, or hyper-operations.json as the entry schema document), a "$recursiveRoot" will be set, so it is important that these references are "$recursiveRef" rather than "$ref".

},
"nonNegativeInteger": {
"type": "integer",
Expand Down Expand Up @@ -55,13 +56,13 @@
},
"$defs": {
"type": "object",
"additionalProperties": { "$ref": "#" },
"additionalProperties": { "$recursiveRef": "#" },
"default": {}
},
"definitions": {
"$comment": "While no longer an official keyword as it is replaced by $defs, this keyword is retained in the meta-schema to prevent incompatible extensions as it remains in common use.",
"type": "object",
"additionalProperties": { "$ref": "#" },
"additionalProperties": { "$recursiveRef": "#" },
"default": {}
},
"title": {
Expand Down Expand Up @@ -101,10 +102,10 @@
"type": "string",
"format": "regex"
},
"additionalItems": { "$ref": "#" },
"additionalItems": { "$recursiveRef": "#" },
"items": {
"anyOf": [
{ "$ref": "#" },
{ "$recursiveRef": "#" },
{ "$ref": "#/$defs/schemaArray" }
],
"default": true
Expand All @@ -115,32 +116,37 @@
"type": "boolean",
"default": false
},
"contains": { "$ref": "#" },
"contains": { "$recursiveRef": "#" },
"maxProperties": { "$ref": "#/$defs/nonNegativeInteger" },
"minProperties": { "$ref": "#/$defs/nonNegativeIntegerDefault0" },
"required": { "$ref": "#/$defs/stringArray" },
"additionalProperties": { "$ref": "#" },
"additionalProperties": { "$recursiveRef": "#" },
"properties": {
"type": "object",
"additionalProperties": { "$ref": "#" },
"additionalProperties": { "$recursiveRef": "#" },
"default": {}
},
"patternProperties": {
"type": "object",
"additionalProperties": { "$ref": "#" },
"additionalProperties": { "$recursiveRef": "#" },
"propertyNames": { "format": "regex" },
"default": {}
},
"dependencies": {
"type": "object",
"additionalProperties": {
"anyOf": [
{ "$ref": "#" },
{ "$ref": "#/$defs/stringArray" }
]
"$recursiveRef": "#"
}
},
"propertyNames": { "$ref": "#" },
"requiredDependencies": {
"type": "object",
"additionalProperties": {
"$ref": "#/$defs/stringArray"
}
},
"propertyNames": {
"additionalProperties": { "$recursiveRef": "#" }
},
"const": true,
"enum": {
"type": "array",
Expand All @@ -162,13 +168,13 @@
"format": { "type": "string" },
"contentMediaType": { "type": "string" },
"contentEncoding": { "type": "string" },
"if": {"$ref": "#"},
"then": {"$ref": "#"},
"else": {"$ref": "#"},
"if": { "$recursiveRef": "#" },
"then": { "$recursiveRef": "#" },
"else": { "$recursiveRef": "#" },
"allOf": { "$ref": "#/$defs/schemaArray" },
"anyOf": { "$ref": "#/$defs/schemaArray" },
"oneOf": { "$ref": "#/$defs/schemaArray" },
"not": { "$ref": "#" }
"not": { "$recursiveRef": "#" }
},
"default": true
}