Producing a JSON schema or an error as a result of parsing JSON value

Schema

flowchart LR
    subgraph inputs
        input_desc_0["JSON value"]
    end
    subgraph output
        output_desc["a JSON schema or an error"]
    end
    inputs --> output

Context

JSON schema is commonly expressed in a JSON format. However, not every JSON is a valid JSON schema.

Examples

producing a JSON schema or an error as a result of parsing a boolean JSON value

Because a boolean value of false is a valid schema which passes validation of any JSON value, such a value represents a JSON schema.

Input:

a boolean JSON value:

false

Output:

a successfully parsed JSON schema:

false

producing a JSON schema or an error as a result of parsing A JSON object with 'type' property set to an array with a single 'null' string inside it

Because the 'type' keyword defines acceptable JSON types. It can be in a form of an array of string (here, only with one type defined), such a value represents a JSON schema.

Input:

A JSON object with 'type' property set to an array with a single 'null' string inside it:

{
  "type": [
    "null"
  ]
}

Output:

a successfully parsed JSON schema:

{
  "type": [
    "null"
  ]
}

producing a JSON schema or an error as a result of parsing A JSON object with 'type' property defined

Because the 'type' keyword defines acceptable JSON types. It can be in a form of a single string, such a value represents a JSON schema.

Input:

A JSON object with 'type' property defined:

{
  "type": "null"
}

Output:

a successfully parsed JSON schema:

{
  "type": [
    "null"
  ]
}

producing a JSON schema or an error as a result of parsing A JSON object with 'required' property being array of strings

Because the 'required' constrain rejects any JSON object not containing properties defined by it, such a value represents a JSON schema.

Input:

A JSON object with 'required' property being array of strings:

{
  "required": [
    "prop1",
    "prop2"
  ]
}

Output:

a successfully parsed JSON schema:

{
  "required": [
    "prop1",
    "prop2"
  ]
}

producing a JSON schema or an error as a result of parsing A JSON object with 'type' property set to an array with 'array', 'null' and 'string' strings inside it

Because the 'type' keyword defines acceptable JSON types. It can be in a form of an array of string (here, with three types defined), such a value represents a JSON schema.

Input:

A JSON object with 'type' property set to an array with 'array', 'null' and 'string' strings inside it:

{
  "type": [
    "array",
    "null",
    "string"
  ]
}

Output:

a successfully parsed JSON schema:

{
  "type": [
    "array",
    "null",
    "string"
  ]
}

producing a JSON schema or an error as a result of parsing A JSON object with 'uniqueItems' property set

Because the 'uniqueItems' keyword makes sure that if JSON value is an array, its items do not contain any duplicates, such a value represents a JSON schema.

Input:

A JSON object with 'uniqueItems' property set:

{
  "uniqueItems": true
}

Output:

a successfully parsed JSON schema:

{
  "uniqueItems": true
}

producing a JSON schema or an error as a result of parsing A JSON object with 'type' property set to an empty array

Because the 'type' keyword defines acceptable JSON types. It can be in a form of an array of string (here, with no types defined), such a value represents a JSON schema.

Input:

A JSON object with 'type' property set to an empty array:

{
  "type": []
}

Output:

a successfully parsed JSON schema:

{
  "type": []
}

producing a JSON schema or an error as a result of parsing a JSON value not being a boolean or object

Because booleans and objects are the only acceptable forms, such a value does not represent a JSON schema.

Input:

a JSON value not being a boolean or object:

0

Output:

a parsing error:

an error:

"the JSON value is neither a boolean nor an object"

producing a JSON schema or an error as a result of parsing an JSON object with the 'not' property defined

Because the 'not' constrain rejects any JSON value which conform to schema defined by it, such a value represents a JSON schema.

Input:

an JSON object with the 'not' property defined:

{
  "not": true
}

Output:

a successfully parsed JSON schema:

{
  "not": true
}

producing a JSON schema or an error as a result of parsing an JSON object with the 'items' property defined

Because the 'items' constrain makes sure than if a JSON value is an array, every item of that array conforms the schema defined by it, such a value represents a JSON schema.

Input:

an JSON object with the 'items' property defined:

{
  "items": true
}

Output:

a successfully parsed JSON schema:

{
  "items": true
}

producing a JSON schema or an error as a result of parsing an empty JSON object

Because an empty JSON object is a valid schema which passes validation of any JSON value, such a value represents a JSON schema.

Input:

an empty JSON object:

{}

Output:

a successfully parsed JSON schema:

{}