[BUG][typescript-fetch] Schema with type object generates undefined function

[rzane]

Description

I'm generating a typescript-fetch client using OpenAPI Generator 4.0.0-beta. After running the generator, the following functions are included in the output, but they are not defined:

• anyFromJSON
• anyToJSON

Also, the type for the property is any, but it should be object I think?

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:
      required:
        - data
      properties:
        data:
          type: object

Command line used for generation

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

Steps to reproduce

I've created a gist that should help to reproduce the issue.

$ git clone https://gist.github.com/rzane/724ad1ed08721d04966f121461c0737d 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:31:17 - error TS2304: Cannot find name 'anyFromJSON'.

31         'data': anyFromJSON(json['data']),
                   ~~~~~~~~~~~

src/models/Example.ts:40:17 - error TS2304: Cannot find name 'anyToJSON'.

40         'data': anyToJSON(value.data),
                   ~~~~~~~~~

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

export interface Example {
    /**
     * 
     * @type {any}
     * @memberof Example
     */
    data: any;
}

export function ExampleFromJSON(json: any): Example {
    return {
        'data': anyFromJSON(json['data']),
    };
}

export function ExampleToJSON(value?: Example): any {
    if (value === undefined) {
        return undefined;
    }
    return {
        'data': anyToJSON(value.data),
    };
}

Related issues/PRs

I couldn't find one 🤷‍♂️

Suggest a fix

Ideally, the property data would be declared as object or empty interface ExampleItems, rather than any.

More importantly, if the schema is an object without any properties or additionalProperties, there should be no coercion.

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[keesvanlierop]

No updates on this one? I think in the mustache template there should be a condition to check if the datatype that is interpolated is not of type any and just render the value for the field.

[rzane]

Definitely agree, though it's not so simple, because you can't do if value == 'any' in a mustache template, which is really inconvenient.

From what I can tell, it seems like the typescript-fetch client was changed to try to serialize and deserialize objects for the sole purpose of parsing and serializing dates. It's nice that it supports dates, but it also doubles the bundle size of the generated code and increases the complexity immensely. The changes broke a ton of the functionality that was working fine. In this case, I really don't think the benefit of date support was worth all of the negatives that come with the change.

[wing328]

I'll take a look tomorrow. Likely it's an issue with the type mapping.

From what I understand, the correct type should be object. Please correct me if I'm wrong.

(Disclaimer: no expert in TS)

[wing328]

I've filed #2453 to fix the issue and got the following Example.ts

// tslint:disable
/**
 * MyAPI
 * MY API
 *
 * OpenAPI spec version: 0.0.0
 *
 *
 * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
 * https://openapi-generator.tech
 * Do not edit the class manually.
 */

import { exists } from '../runtime';
/**
 *
 * @export
 * @interface Example
 */
export interface Example {
    /**
     *
     * @type {object}
     * @memberof Example
     */
    data: object;
}

export function ExampleFromJSON(json: any): Example {
    return {
        'data': json['data'],
    };
}

export function ExampleToJSON(value?: Example): any {
    if (value === undefined) {
        return undefined;
    }
    return {
        'data': value.data,
    };
}

[yskkin]

This is not fixed if request is application/x-www-form-urlencoded.

    post:
      operationId: create-foo
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Foo'
      requestBody:
        content:
          application/x-www-form-urlencoded:
            schema:
              $ref: '#/components/schemas/Foo

[Londeren]

This is not fixed if request is multipart/form-data either:

"requestBody": {
    "required": true,
    "content": {
        "multipart\/form-data": {
            "schema": {
                "properties": {
                    "file": {
                        "description": "File content",
                        "type": "file"
                    }
                },
                "type": "object"
            }
        }
    }
},

[mstojanovic8]

Hi, bumping this as it appears to have regressed in recent versions.

We are using openapi-generator-cli v7.23.0 with the typescript-fetch generator and hitting the exact same issue — anyToJSON is not defined at runtime for endpoints that have any-typed properties (e.g. photo, image, document fields sent as form data blobs).

The generated code references anyToJSON(...) directly:

formParams.append('photo', new Blob([JSON.stringify(anyToJSON(requestParameters['photo']))], { type: "application/json" }));

But anyToJSON is never defined in runtime.ts, causing a ReferenceError at runtime.

This was supposedly fixed in PR #2453 back in 2019, but it appears to be broken again in 7.23.0. Could someone confirm whether this is a known regression and if there's a tracked fix or workaround on the roadmap?

As a workaround we are manually adding anyToJSON to runtime.ts and protecting it from being overwritten via .openapi-generator-ignore, but this is not sustainable for an automated SDK generation pipeline.

Is there a version where this is fixed, or is a fix planned?