Description

With the Typescript-angular generator, JSON query parameters are not serialized as JSON.
Instead each field of the object is added independently.

Example (see OpenAPI specification below),

For the following call

const filter = {name: 'John', age: 37};
service.search(filter).subscribe();

I expect a request to http://localhost/search?filter=%7B%22name%22%3A%22John%22%2C%22age%22%3A37%7D (URL encoded JSON)

But instead it requests http://localhost/search?name=John&age=37

On this branch, I've started to implement tests showing the issue and trying to implement a solution.

openapi-generator version

7.15.0 (was working with 7.4.0, I do not know in which version it stopped to work).

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: query-param-json
  version: 1.0.0
paths:
  /search:
    get:
      operationId: search
      parameters:
        - in: query
          name: filter
          description: Filter
          required: false
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Filter'

      responses:
        '200':
          description: Ok
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Response'

components:
  schemas:
    Item:
      type: object
      required:
        - name
        - age
      properties:
        name:
          type: string
          description: The name
        age:
          type: integer
          minimum: 0
          default: 5
          nullable: false
          description: The age

    Response:
      type: object
      required:
        - items
      properties:
        items:
          type: array
          description: Array of items.
          nullable: false
          items:
            $ref: '#/components/schemas/Item'

    Filter:
      type: object
      properties:
        name:
          type: string
          description: The name
        age:
          type: integer
          minimum: 0
          default: 5
          nullable: false
          description: The age

Generation Details

Typescript-angular

Steps to reproduce

Generate and call the search operation of the service, query params will not be JSON

Related issues/PRs

One must be careful, there seems to have been already several issues regarding the serialization of query parameters for this generator.
A few recent

• [typescript-angular] fix: correctly serialize query params objects #20850
• [Feat][Typescript Angular] Implement deepObject query params (OAS3.0) #21108

Suggest a fix

The issue is that when the method addToHttpParams() of the file modules/openapi-generator/src/main/resources/typescript-angular/api.base.service.mustache is called, we have already lost the information that the parameter must be in JSON.
In some way, this must be provided from `modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache``

I've started to implement a fix in master...VladimirSvoboda:openapi-generator:AngularJsonQueryParam

However, due to the lack of tests regarding all the kind of different query parameters serialization, there is a risk that I introduce other regressions.
The fix is not ready yet as I have observed a regression.