[BUG][typescript-fetch] Further union issues

[felschr]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issuue still exists?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

With #6789 merged I regenerated my client and unfortunately there are still some union-related errors.

There are multiple locations with invalid code generated for handling union values:

        return new runtime.JSONApiResponse(response, (jsonValue) => jsonValue.map(Pet | Cat | DogFromJSON));

        const response = await this.request({
            path: `/pets`,
            method: 'POST',
            headers: headerParameters,
            query: queryParameters,
            body: Pet | Cat | DogToJSON(requestParameters.petCatDog),
        });

No errors are thrown during generation but when compiling with typescript it's failing.

openapi-generator version

openapi-generator-cli-5.0.0-20200907.080402-621.jar

OpenAPI declaration file content or url

openapi: "3.0.1"
info:
  version: 1.0.0
  title: typescript union issue
paths:
  /pets:
    get:
      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                type: array
                items:
                  oneOf:
                    - $ref: "#/components/schemas/Pet"
                    - $ref: "#/components/schemas/Cat"
                    - $ref: "#/components/schemas/Dog"
                  discriminator:
                    mapping:
                      cat: "#/components/schemas/Cat"
                      dog: "#/components/schemas/Dog"
                    propertyName: "petType"
    post:
      requestBody:
        content:
          application/json:
            schema:
              oneOf:
                - $ref: "#/components/schemas/Pet"
                - $ref: "#/components/schemas/Cat"
                - $ref: "#/components/schemas/Dog"
              discriminator:
                mapping:
                  cat: "#/components/schemas/Cat"
                  dog: "#/components/schemas/Dog"
                propertyName: "petType"
      responses:
        "201":
          description: Created
  /pets-alt:
    get:
      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/PetsResponse"
components:
  schemas:
    Pet:
      type: object
      required:
        - petType
      properties:
        petType:
          type: string
        name:
          type: string
    Cat:
      type: object
      allOf:
        - $ref: "#/components/schemas/Pet"
        - type: object
          properties:
            scratching:
              type: boolean
    Dog:
      type: object
      allOf:
        - $ref: "#/components/schemas/Pet"
        - type: object
          properties:
            sniffing:
              type: boolean
    PetsResponse:
      type: object
      properties:
        pets:
          type: array
          items:
            oneOf:
              - $ref: "#/components/schemas/Pet"
              - $ref: "#/components/schemas/Cat"
              - $ref: "#/components/schemas/Dog"
            discriminator:
              mapping:
                cat: "#/components/schemas/Cat"
                dog: "#/components/schemas/Dog"
              propertyName: "petType"

Generation Details

Generator: typescript-fetch
Config:

{
  "npmName": "@company/project",
  "npmVersion": "1.0.0",
  "snapshot": false,
  "supportsES6": true,
  "typescriptThreePlus": true
}

Steps to reproduce

This issue can be reproduced by using the typescript-fetch generator with the OpenAPI declaration & config from above.

Related issues/PRs

#6789
#6513

Suggest a fix

[macjohnny]

@felschr would you like to implement a fix?

[macjohnny]

you could also try the newly refactored https://openapi-generator.tech/docs/generators/typescript

[felschr]

I don't think I'm able to implement it myself.
Also the new experimental typescript generator doesn't seem to support unions at all according to the docs. I've just tried using it but the resulting code also fails to compile.

[CarltonHowell]

I'm hitting the same issue with an OpenAPi spec using oneOf. Any progress on this one?

[tschmorleiz]

We are hitting the same issue here; any progress on this one or suggestions on where to start to fix it myself?

[macjohnny]

@tschmorleiz https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator/src/main/resources/typescript-fetch
https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptFetchClientCodegen.java

[fantapop]

I don't think enough information is currently being generated to solve this in the template alone. I've printed out all the data available:

In my case, my spec shows:

"media-key": {
    "oneOf": [
        {
            "$ref": "#/components/schemas/MediaSizeName"
        },
        {
            "$ref": "#/components/schemas/MediaName"
        }
    ]
},

Both MediaSizeName and MediaName are string enum

The generated code is:

        'media_key': !exists(json, 'media-key') ? undefined : MediaSizeName | MediaNameFromJSON(json['media-key']),

And here is all the data available in the template to generate this line of code:

CodegenProperty{openApiType='MediaSizeName | MediaName', baseName='media-key', complexType='MediaSizeName | MediaName', getter='getMediaKey', setter='setMediaKey', description='null', dataType='MediaSizeName | MediaName', datatypeWithEnum='MediaSizeName | MediaName', dataFormat='null', name='media_key', min='null', max='null', defaultValue='undefined', defaultValueWithParam=' = data.media-key;', baseType='MediaSizeName | MediaName', containerType='null', title='null', unescapedDescription='null', maxLength=null, minLength=null, pattern='null', example='null', jsonSchema='{
  "oneOf" : [ {
    "$ref" : "#/components/schemas/MediaSizeName"
  }, {
    "$ref" : "#/components/schemas/MediaName"
  } ]
}', minimum='null', maximum='null', exclusiveMinimum=false, exclusiveMaximum=false, hasMore=true, required=false, deprecated=false, secondaryParam=false, hasMoreNonReadOnly=false, isPrimitiveType=false, isModel=true, isContainer=false, isString=false, isNumeric=false, isInteger=false, isLong=false, isNumber=false, isFloat=false, isDouble=false, isByteArray=false, isBinary=false, isFile=false, isBoolean=false, isDate=false, isDateTime=false, isUuid=false, isUri=false, isEmail=false, isFreeFormObject=false, isListContainer=false, isMapContainer=false, isEnum=false, isReadOnly=false, isWriteOnly=false, isNullable=false, isSelfReference=false, isCircularReference=false, isDiscriminator=false, _enum=null, allowableValues=null, items=null, mostInnerItems=null, vendorExtensions={}, hasValidation=false, isInherited=false, discriminatorValue='null', nameInCamelCase='MediaKey', nameInSnakeCase='MEDIA_KEY', enumName='null', maxItems=null, minItems=null, maxProperties=null, minProperties=null, uniqueItems=false, multipleOf=null, isXmlAttribute=false, xmlPrefix='null', xmlName='null', xmlNamespace='null', isXmlWrapped=false}*/

To really generate correct code here using that same FromJSON / ToJSON format we'd need to know the sub types of MediaSizeName and MediaName but here we don't even have the names broken out into separate words. I'm hopeful that #3162 will provide the additional data required to render this code correctly. This is a huge change that seems to be affecting everything so its been a long time coming. In the meantime, I wonder if there is something we can do that helps it work most of the time.

[fantapop]

I've stared at this for a while now and I haven't come up with anything promising. One thought I had was that if the value is a primitive type, the toJSON and fromJSON functions are essentially just returning the value with a type assertion. In object types, the toJSON/fromJSON functions are important to remap the names of the keys. If we could determine that this was a union type we could bypass the toJSON/fromJson function for this value and at least it would work for primitive types.

generated code would look something like:

 'media_key': !exists(json, 'media-key') ? undefined : json['media-key'] as MediaSizeName | MediaName,

Unfortunately, determining that its a union is non-trivial without modifying the core (assuming mustache is the templating language). It would be great if there was a sideloading mechanism for custom mustache lambdas that could live alongside a loaded template. I did notice second class support for handlebars which seems interesting. I did make an attempt to migrate the typescript-fetch templates to handlebars but there were a lot of built ins that would need to be converted. Modifying the core seems like a likely requirement in that path as well.

[fantapop]

Another idea which might work as a stop gap is to use the post processing functionality to fix these. I'll give that a go this evening.