Tuple items with minItems and additionalItems

[epferrari]

We have a use case I don't think is currently covered. We have an array where 2 items must be defined, a max of 3, and the first one has an additional constraint. JsonSchema allows for this, but the generated type isn't what we'd expect.

schema:

{
  "title": "Foo",
  "type": "array",
  "minItems": 2,
  "maxItems": 3,
  "definitions": {
    "foo_0": {
      "title": "Foo Item",
      "type": "integer",
      "exclusiveMinimum": 0
    },
    "foo_n": {
      "title": "Foo Item",
      "type": "integer"
    }
  },
  "items": [{
    "$ref": "#/definitions/foo_0"
  }, {
    "$ref": "#/definitions/foo_n"
  }],
  "additionalItems": {
    "$ref": "#/definitions/foo_n"
  }
}

expected generated ts:

export type Foo = [FooItem, FooItem1, FooItem1?];
export type FooItem = number;
export type FooItem1 = number;

actual generated ts:

export type Foo = [FooItem, FooItem1];
export type FooItem = number;
export type FooItem1 = number;

using version 6.1.1

[bcherny]

This is a fun one :)

• Bug Ensure that code complies with official JSON-schema test suite #1 is when we infer a tuple type, we should look to additionalItems as the spread property. In your example, the correct type to generate is [FooItem, FooItem1, ...FooItem1[]].
• Enhancement Support custom JSON-schema extensions #2 is we should take minLength and maxLength into account when specifying tuple types. As a first pass:
  1. When minLength !== items.length, we should throw a validation error
  2. When maxLength is defined, we should generate optional tuple properties (eg. FooItem1?) instead of a rest property (eg. ...FooItem1).

Want to take a shot at Bug 1?