[BUG][typescript-fetch] Adding new discriminators to polymorph classes breaks clients

[aeneasr]

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 issue still exists?
• Have you searched 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

Let's say we are adding a new discriminator type to the API matching this description:

https://github.com/ory/kratos/blob/ef9ee235866c6f3958574d2e98f09de3ca1e83af/spec/api.json#L2452-L2462

Let's say it's

          "mapping": {
            "a": "#/components/schemas/uiNodeAnchorAttributes",
            "img": "#/components/schemas/uiNodeImageAttributes",
            "input": "#/components/schemas/uiNodeInputAttributes",
            "script": "#/components/schemas/uiNodeScriptAttributes",
            "text": "#/components/schemas/uiNodeTextAttributes",
+          "div": "#/components/schemas/uiNodeDivisionAttributes"
          },

If we have an SDK client generated prior to this change, and it tries to parse the request, we end up with an exception:

Error: No variant of UiNodeAttributes exists with 'node_type=div'
    at UiNodeAttributesFromJSONTyped (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiNodeAttributes.js:44:19)
    at UiNodeAttributesFromJSON (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiNodeAttributes.js:26:12)
    at UiNodeFromJSONTyped (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiNode.js:81:71)
    at UiNodeFromJSON (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiNode.js:74:12)
    at Array.map (<anonymous>)
    at UiContainerFromJSONTyped (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiContainer.js:46:33)
    at UiContainerFromJSON (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/UiContainer.js:36:12)
    at LoginFlowFromJSONTyped (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/LoginFlow.js:86:53)
    at LoginFlowFromJSON (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/models/LoginFlow.js:63:12)
    at JSONApiResponse.transformer (/Users/aeneas/workspace/go/cloud-shard-1/sdktest/node_modules/@ory/client-fetch/dist/apis/FrontendApi.js:307:103)

openapi-generator version

7.12.0

OpenAPI declaration file content or url

https://github.com/ory/kratos/blob/ef9ee235866c6f3958574d2e98f09de3ca1e83af/spec/api.json

Generation Details

We have enabled enumUnknownDefaultCase in the generator config:

npmName: "${NPM_NAME}-fetch"
npmVersion: $VERSION
# typescriptThreePlus: true
supportsES6: true
ensureUniqueParams: true
modelPropertyNaming: original
disallowAdditionalPropertiesIfNotPresent: false
withInterfaces: false
useSingleRequestParameter: true
enumUnknownDefaultCase: true

Steps to reproduce

test.js

const nock = require('nock');
const f = require('@ory/client-fetch');

const body = {
    "id": "830d9a9a-56a1-4569-b093-73e290a88660",
    "type": "browser",
    "expires_at": "2025-03-05T10:53:48.504179456Z",
    "issued_at": "2025-03-05T09:53:48.504179456Z",
    "request_url": "https://jolly-napier-yycikmm17f.projects.oryapis:8080/self-service/registration/browser",
    "ui": {
        "action": "https://jolly-napier-yycikmm17f.projects.oryapis:8080/self-service/registration?flow=830d9a9a-56a1-4569-b093-73e290a88660",
        "method": "POST",
        "nodes": [
            {
                "type": "div",
                "group": "captcha",
                "attributes": {
                    "id": "captcha_turnstile_inject",
                    "node_type": "div"
                },
                "messages": [],
                "meta": {}
            }
        ]
    },
    "organization_id": null,
    "state": "choose_method"
}


const oryf = new f.FrontendApi(
    new f.Configuration({
        basePath: 'http://localhost:4455',
    })
);

// Set up the mock endpoint for createNativeLoginFlow
nock('http://localhost:4455')
    .get("/self-service/login/api")
    .reply(200,body
    );

// Set up the mock endpoint for createNativeLoginFlow
nock('http://localhost:4455')
    .get("/self-service/login/browser")
    .reply(200, body)

oryf.createNativeLoginFlow({}).then((res) => {
    console.log(res);
});

oryf.createBrowserLoginFlow({}).then((res) => {
    console.log(res);
});

package.json

{
  "dependencies": {
    "@ory/client-fetch": "1.19.0",
    "nock": "^14.0.1"
  }
}

Related issues/PRs

Could not find any. However, in the regular typescript generator (with axios) this problem does not exist.

Suggest a fix

If a mapping or field is unknown, the client code should never break, otherwise it is impossible to make additive changes to an existing API.

[aeneasr]

This is the generated code in question:

function UiNodeAttributesToJSONTyped(value, ignoreDiscriminator = false) {
    if (value == null) {
        return value;
    }
    switch (value['node_type']) {
        case 'a':
            return Object.assign({}, (0, UiNodeAnchorAttributes_1.UiNodeAnchorAttributesToJSON)(value), { node_type: 'a' });
        case 'img':
            return Object.assign({}, (0, UiNodeImageAttributes_1.UiNodeImageAttributesToJSON)(value), { node_type: 'img' });
        case 'input':
            return Object.assign({}, (0, UiNodeInputAttributes_1.UiNodeInputAttributesToJSON)(value), { node_type: 'input' });
        case 'script':
            return Object.assign({}, (0, UiNodeScriptAttributes_1.UiNodeScriptAttributesToJSON)(value), { node_type: 'script' });
        case 'text':
            return Object.assign({}, (0, UiNodeTextAttributes_1.UiNodeTextAttributesToJSON)(value), { node_type: 'text' });
        default:
            throw new Error(`No variant of UiNodeAttributes exists with 'node_type=${value['node_type']}'`); // <- breaks any non-conformative node type. Instead just return value.
    }
}