Support Pick and other Mapped Types

Hi! Great library here. We are heavily experimenting with using json schemas generated from our TypeScript interfaces on both front end and back end and this is obviously the glue that’s holding it all together! With that said, there are some scenarios we are encountering that we are having to work around to get our schemas generated the way we want to, the main issues being around Mapped Types.

Consider the following interfaces:

export interface ISortableProperties {
    /**
     * @description id
     */
    id: number;

    /**
     * @description name
     */
    name: string;

    /**
     * @description date
     */
    date: Date;
}

export interface IResponse {
    unsortableProperty: string;
}

export interface IRequest {
    sortBy: Sortify<Pick<ISortableProperties, "id">> | Sortify<Pick<ISortableProperties, "name">> | Sortify<Pick<ISortableProperties, "date">>
}

export type Sortify<T> = {
    [P in keyof T]: sorting.SortDirection
}

The schema I’d like to see from this is

{
  "$schema": "http://json-schema.org/draft-06/schema#",
  "additionalProperties": false,
  "definitions": {
    "sorting.SortDirection": {
      "enum": [
        "ASC",
        "DESC"
      ],
      "type": "string"
    }
  },
  "properties": {
    "sortBy": {
      "anyOf": [
        {
          "additionalProperties": false,
          "properties": {
            "id": {
              "$ref": "#/definitions/sorting.SortDirection",
              "description": "id"
            }
          },
          "required": [
            "id"
          ],
          "type": "object"
        },
        {
          "additionalProperties": false,
          "properties": {
            "name": {
              "$ref": "#/definitions/sorting.SortDirection",
              "description": "name"              
            }
          },
          "required": [
            "name"
          ],
          "type": "object"
        },
        {
          "additionalProperties": false,
          "properties": {
            "date": {
              "$ref": "#/definitions/sorting.SortDirection",
              "description": "date"              
            }
          },
          "required": [
            "date"
          ],
          "type": "object"
        }
      ]
    }
  },
  "required": [
    "sortBy"
  ],
  "type": "object"
}

But I actually get the error : ts-json-schema-generator\dist\ts-json-schema-generator.js:30 throw error; ^

TypeError: Cannot read property ‘reduce’ of undefined.

Is there any possibility of supporting this kind of scenario?

Thanks! Rob

[domoritz]

Fixed in #ebad910

[renewooller]

Well, I’ve got an ugly(?) implementation working for Partial. Will test and do a pull request.