[BUG][typescript-fetch] Additional properties are treated as array

[rzane]

Description

Description

I'm generating a typescript-fetch client using OpenAPI Generator 4.0.0-beta. After running the generator, I notice that the resulting code attempts to coerce a dictionary to an array. According the documentation, a dictionary can be defined by specifying additionalProperties.

openapi-generator version

4.0.0-beta

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: MyAPI
  description: MY API
  version: 0.0.0
servers:
  - url: http://localhost:8080/api/
paths:
  /example:
    get:
      operationId: getExample
      responses:
        "200":
          description: "Success"
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Example"

components:
  schemas:
    Example:
      type: object
      required:
        - items
      properties:
        items:
          type: object
          additionalProperties:
            type: object
            required:
              - name
            properties:
              name:
                type: string

Command line used for generation

$ node_modules/.bin/openapi-generator generate -i openapi.yaml -o src -g typescript-fetch

Steps to reproduce

$ git clone https://gist.github.com/rzane/99f6106c72bead20faf39c8ad004c4d0 bug-report
$ cd bug-report
$ npm install
$ npm run generate
$ npm run test

You should see the following output:

> tsc -p src --noEmit

src/models/Example.ts:37:9 - error TS2322: Type 'ExampleItems[]' is not assignable to type '{ [key: string]: ExampleItems; }'.
  Index signature is missing in type 'ExampleItems[]'.

37         'items': (json['items'] as Array<any>).map(ExampleItemsFromJSON),
           ~~~~~~~

  src/models/Example.ts:32:5
    32     items: { [key: string]: ExampleItems; };
           ~~~~~
    The expected type comes from property 'items' which is declared here on type 'Example'

src/models/Example.ts:46:19 - error TS2352: Conversion of type '{ [key: string]: ExampleItems; }' to type 'any[]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type '{ [key: string]: ExampleItems; }' is missing the following properties from type 'any[]': length, pop, push, concat, and 25 more.

46         'items': (value.items as Array<any>).map(ExampleItemsToJSON),
                     ~~~~~~~~~~~~~~~~~~~~~~~~~

The source of the error can be found in src/models/Example.ts, which contains the following:

export function ExampleFromJSON(json: any): Example {
    return {
        'items': (json['items'] as Array<any>).map(ExampleItemsFromJSON),
    };
}

export function ExampleToJSON(value?: Example): any {
    if (value === undefined) {
        return undefined;
    }
    return {
        'items': (value.items as Array<any>).map(ExampleItemsToJSON),
    };
}

Related issues/PRs

I couldn't find one 🤷‍♂️

Suggest a fix

Add a mapValues function to the runtime.ts file:

export function mapValues(data: object, fn: (item: any) => any) {
  return Object.keys(data).reduce(
    (acc, key) => ({ ...acc, [key]: fn(data[key]) }),
    {}
  );
}

Then, in the case of a dictionary, change the above implementation to:

export function ExampleFromJSON(json: any): Example {
  return {
    items: mapValues(json["items"], ExampleItemsFromJSON)
  };
}

export function ExampleToJSON(value?: Example): any {
  if (value === undefined) {
    return undefined;
  }
  return {
    items: mapValues(value.items, ExampleItemsToJSON)
  };
}

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[ehvattum]

Checking if it is a map is checking the isMapContainer value in the mustache.

I'm currently attempting to implement your suggested fix @rzane