patternGroups and patternRequired (v5 proposal) - sgpinkus/json-schema GitHub Wiki

THIS WIKI IS OBSOLETE. PLEASE SEE THE NEW JSON-SCHEMA-ORG/JSON-SCHEMA-SPEC REPOSITORY.

NOTE: Added to new org as issue: https://github.com/json-schema-org/json-schema-spec/issues/117

Proposed keywords

This proposal would introduce two new keywords:

  • patternGroups and patternRequired

these keywords would complement the existing keyword:

  • patternProperties

Purpose

Currently, schemas can specify a minimum/maximum number of object properties, but they cannot place such constraints on particular groups of properties.

This proposal basically allows us to specify the number of properties that must match a particular pattern.

Values

patternGroups

The value of patternGroups would be an object. The keys of the object would be regular expressions (exactly like the existing patternProperties).

The values inside patternGroups would be objects, containing zero or more of the following properties:

  • minimum - the minimum number of properties in the data that MUST match the corresponding pattern
  • maximum - the maximum number of properties in the data that MUST match the corresponding pattern
  • schema - the schema that matching properties must follow.

minimum/maximum would be non-negative integers, and schema would be a schema.

patternRequired

The value of this keyword should be the array of patterns (to require at least one property matching the pattern)

Behaviour

patternGroups

If the instance is an object, then for every entry in patternGroups:

  1. the set of properties matching that pattern is collected
  2. if minimum or maximum are specified in the patternGroups entry, then the size of this property set must be between these values (inclusive)
  3. if schema is specified in the patternGroups entry, then for every property in the property set, the corresponding object member in the instance must follow that schema.

patternRequired

If the instance is an object, the data to be valid should have at least one property matching each pattern (the same property can match multiple patterns).

Example patternGroups

{
    "type": "object",
    "patternGroups": {
        "^[a-z]+$": {
            "minimum": 1,
            "schema": {"type": "string"}
        },
        "^[0-9]+$": {
            "minimum": 1,
            "schema": {"type": "integer"}
        }
    }
}

Example with patternRequired

{
    "type": "object",
    "patternProperties": {
        "^[a-z]+$": {"type": "string"},
        "^[0-9]+$": {"type": "integer"}
    },
    "patternRequired": ["^[a-z]+$", "^[0-9]+$"]
}

Both these schemas expresses the constraint that instance objects must have at least one alphabetic key, and at least one numeric-key. (This constraint is currently not possible to express).

Additionally, the alphabetic keys must hold strings, and the numeric keys must hold integers.

Valid: {"abc": "foo", "123": 456} Invalid: {"abc": "foo", "def": "bar"}

For the simple case the syntax of patternRequired is the simpler and consistent with properties/required.