Leyman

Strict mode ​

A schema can be valid JSON Schema and still be a mistake. Validators ignore these, so the schema silently accepts more, or less, than it appears to. Strict mode (the default) fails on them with a GeneverStrictModeError, whose pointer names the schema at fault, rather than generating a type that hides the problem.

Keywords that do nothing ​

  • An unknown keyword, such as a misspelled maxLenght. Keywords starting with x- are allowed, as are OpenAPI's keywords in an OpenAPI document or with openApi30.
  • A type specific keyword in a schema without a type, or whose type it doesn't apply to, such as maxLength on a number. Subschemas of allOf, anyOf, oneOf, if/then/else and not inherit their parent's type.
  • A required property that isn't in properties, of the schema or a parent.
  • then or else without if.
  • A discriminator whose property isn't required, by the schema or by every oneOf/anyOf branch, or whose mapping names a schema that doesn't exist. Its values aren't checked, as OpenAPI may take them from component names.

Schemas that accept nothing, or less than they declare ​

  • minLength greater than maxLength, and the same for minItems/maxItems, minProperties/maxProperties and minContains/maxContains.
  • minimum/exclusiveMinimum and maximum/exclusiveMaximum that no number fits between, or no integer for type: "integer".
  • An enum or const value that isn't of the schema's type.
  • A required property whose schema is never valid (such as false), or more required properties than maxProperties allows.
  • minProperties more than an object with additionalProperties: false can have.
  • A tuple (prefixItems with items: false) shorter than minItems, or longer than maxItems.
  • A $ref back to a schema it is part of, without a property or item in between, such as { "anyOf": [{ "$ref": "#" }, { "type": "string" }] }. It applies to the same value again, so a validator never finishes checking it, and JSON Schema leaves its behaviour undefined.

Every schema Juniper builds passes.

Without strict mode ​

For schemas you don't control, disable strict mode with --no-strict (or strict: false). The type then follows what a validator accepts, and is never narrower:

  • Unknown keywords, and keywords that don't apply to the type, are ignored, as validators ignore them.
  • A schema without a type accepts every type. { "properties": { "a": … } } is the object, or any string, number, boolean, null or array.
  • A type whose constraints contradict each other is never. For { "type": ["string", "null"], "minLength": 3, "maxLength": 2 }, only null is valid.
  • Tuple items beyond maxItems are left out.
  • A $ref back to a schema it is part of, without a property or item in between, is never: it can't be why a value is valid. The anyOf above is string. A schema it passes through on the way back is inlined, as TypeScript rejects a type that refers to itself outside an object or array.

Some features are unsupported in either mode, as ignoring them would loosen the type: $dynamicRef and $recursiveRef throw a GeneverUnsupportedError.