[BUG][typescript-fetch] HTML-escaped values in imports when using "anyOf" enums (OpenAPI 3.0)

[adam-earthscope]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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

I am seeing broken Typescript when generating a client from an OpenAPI 3.0 spec using anyOf with enums.

Older versions of openapi-generator (ex. 7.11.0) work, and setting the OpenAPI spec version to 3.1.0 also works.

openapi-generator version

7.18.0

OpenAPI declaration file content or url

{
  "openapi": "3.0.2",
  "info": {
    "title": "Test",
    "version": "main-20250922183409-dabb5d59"
  },
  "paths": {
    "/test": {
      "get": {
        "summary": "Test API",
        "operationId": "test_api",
        "parameters": [
          {
            "description": "Combined Enums",
            "required": true,
            "schema": {
              "title": "Combined",
              "anyOf": [
                {
                  "$ref": "#/components/schemas/Enum1"
                },
                {
                  "$ref": "#/components/schemas/Enum2"
                }
              ],
              "description": "Combined Enums"
            },
            "example": "value1",
            "name": "combined",
            "in": "query"
          }
        ],
        "responses": {
          "204": {
            "description": "Successful Response"
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "Enum1": {
        "title": "Enum1",
        "enum": ["value1", "value2", "value3"],
        "type": "string",
        "description": "An enumeration."
      },
      "Enum2": {
        "title": "Enum2",
        "enum": ["value4", "value5"],
        "type": "string",
        "description": "An enumeration."
      }
    }
  },
  "tags": []
}

Generation Details

openapi-generator generate -i openapi.json -g typescript-fetch -o client

Steps to reproduce

The resulting code tries to import HTML-escaped string values rather than an enum type:

import * as runtime from '../runtime';
import type {
  'value1',
  'value2',
  'value3',
  'value4',
  'value5',
} from '../models/index';
import {
    'value1'FromJSON,
    'value1'ToJSON,
    'value2'FromJSON,
    'value2'ToJSON,
    'value3'FromJSON,
    'value3'ToJSON,
    'value4'FromJSON,
    'value4'ToJSON,
    'value5'FromJSON,
    'value5'ToJSON,
} from '../models/index';

The generated code should look something like this:

import * as runtime from '../runtime';
import type {
  Combined,
} from '../models/index';
import {
    CombinedFromJSON,
    CombinedToJSON,
} from '../models/index';

Related issues/PRs

There are a bunch of issues that seem similar (#22427, #21587, #19155, #18207) but none that fits this behavior exactly.

Suggest a fix

[wing328]

to use the original value, we need to use {{{ ... }}} instead of {{ ... }} (HTML-escaped value) in the mustache templates: https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator/src/main/resources/typescript-fetch

is that something you can help us fix with a PR? thank you in advance.

[adam-earthscope]

Sorry, I could have been clearer in the original description.

The issue isn't really the HTML escaping, it's that the API is trying to import the enum values rather than the enum type. I updated the description to include what the generated code should look like.