[BUG][TypeScript-Angular] Incorrect Query Parameter Serialization for Objects in OpenAPI Generator v7.12.0

[jayson-gallardo]

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?
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Description

The recent change in OpenAPI Generator introduced by PR #20681 is causing issues with how query parameters are serialized in the generated Angular TypeScript SDK.

Previously, when an object was passed as a query parameter (e.g., {"alias":"test"}), the generator would append each object's property as a separate query parameter. Now, it serializes the entire object, which results in incorrect query parameter construction.

openapi-generator version

The issue arises in OpenAPI Generator version v7.12.0.

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  version: 0.0.22
  title: <title>
  description: <description>
  contact:
    name: ...
    email: ...

paths:
  /instances/lookup:
    get:
      summary: Get instance by alias
      description: Get instance by alias
      operationId: instanceLookup
      security: []
      tags:
        - Instance
      parameters:
        - $ref: "#/components/parameters/instanceAlias"
      responses:
        "200":
          $ref: "#/components/responses/getInstanceConfigResponse"
        "400":
          $ref: "#/components/responses/badRequest"
        "404":
          $ref: "#/components/responses/notFound"

components:
  parameters:
    instanceAlias:
      name: alias
      in: query
      required: true
      description: Instance alias kebab case
      example: "test-alias"
      schema:
        type: string
        additionalProperties: false
        description: Instance alias kebab case
        pattern: '[a-z0-9]+(?:-[a-z0-9]+)*' # kebab-case

Generation Details

The generator was ran as a GitHub action:

name: Generate Angular SDK

on:
  push:
    branches: [ 'main' ]
    paths: [ 'api/openapi.yaml' ]
  workflow_dispatch:

jobs:
  generate-angular-client:
    runs-on: ubuntu-latest
    name: Builder
    steps:
      # Checkout your code
      - name: Checkout
        uses: actions/checkout@v3

      - name: Generate Angular Client
        uses: openapi-generators/openapitools-generator-action@v1
        with:
          openapi-file: api/openapi.yaml
          generator: typescript-angular
...

Steps to reproduce

1. Generate the SDK using the OpenAPI specs
2. Call the generated function instanceLookup({ alias: 'test' }).
3. Observe the generated query parameter string in the resulting GET request.

Expected: https://www.example.com/instances/lookup?alias=test
Actual: https://www.example.com/instances/lookup?alias=%7B%22alias%22%3A%22test%22%7D

Related issues/PRs

The issue appears to be related to PR #20681.

Suggest a fix

The regression seems to be related to the serialization logic where objects are being stringified. The logic should be updated to append individual object properties instead of the entire object being serialized as a string.

[anasbud]

I have the same issue as well.