[BUG] [cpp-qt5-client] Response headers are checked using case sensitive string comparison

Created by: st-agnes

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• 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?
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Description

I've got the following issue with the cpp-qt5-client generator: If the server sends a "content-type" header using lowercase letters for "content-type" (rather than "Content-Type"), the response body isn't read by the client. It seems to me that the issues lays in https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/cpp-qt5-client/HttpRequest.cpp.mustache where a case-sensitive comparison of strings is performed (see method process_response).

openapi-generator version

Version 5.1.0

OpenAPI declaration file content or url

Here's the yaml I'm using - I've shortened it for brevity:

---
openapi: 3.0.0
info:
  title: Team API
  version: 1.0.0-oas3
servers:
- url: https://localhost:5001/api/v1
tags:
- name: authentication
paths:
  /login:
    post:
      operationId: Login
      tags:
      - authentication
      summary: User login
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/LoginRequest'
        required: true
      responses:
        "200":
          description: Successful login
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LoginResponse'
        "400":
          description: Invalid request parameter
        "403":
          description: Invalid login data
components:
  schemas:
    LoginRequest:
      properties:
        teamId:
          type: integer
          example: 12345
        password:
          type: string
          format: password
          example: abcd6789
      required:
        - teamId
        - password
      additionalProperties: false
    LoginResponse:
      type: object
      properties:
        accessToken:
          type: string
          description: User Access token
          example: eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiVGVhbSA0NSIsImlhdCI6MTYxMDgxMjgwMCwiZXhwIjoxNjEwODk5MjAwLCJ0ZWFtSWQiOiI0NSIsInNlc3Npb25JZCI6ImM1MWNlMTVmLTU4MWItMTFlYi05NjY1LTQyMDEwYTljMDA5NiIsInJvbGUiOiJwbGF5ZXIifQ.kguZV64mj7PIDCwQjMzRk2K-ivhD59uVixDIF6v7LkOTQ5kE0n0b-ICHP3xly7iY_0Tp-9shUg-bONwnk2_yuAlv1BVoo18ZE6kNHmvf1nvR6tGxWL4lcBJ1oYg_bPaEHJlSuInEKj-PJKxykPCTPPiqlsZn2ffMfm720qajMpSojFbNZH6CGlqYvC1TBjy1qBD1r-pVqRiSIdJDvAg6dByIbHPJfhoi-xrL2X55GxDpOXdmcKRLOPJ2Jndcaau2IgqkrVE9BxM3i62HGConYxyoKrqzKNnJE9NiWcmzBzihCgtS8COcHDQ_kYHIVGsyiaR4ugy2VC7zijM9CzPq_g
      additionalProperties: false

Generation Details

docker run --rm -v %cd%:/local openapitools/openapi-generator-cli generate -i /local/api/team-api-openapi.yaml -g cpp-qt5-client --additional-properties=cppNamespace=autogen::team,modelNamePrefix=teamapi_ -o /local/autogen/team

Steps to reproduce

1. Generate a client using qt5-client generator, from any yaml file that defines an endpoint with a response containing a body.
2. Create a server that responds with "content-type" rather than "Content-Type" in the header. (For example I'm using asp.net core for the server which does exactly this.)
3. Start server and client
4. From the client make a request to the mentioned endpoint and observe the result.

The response body will be ignored as if no content had been sent by the server.

Related issues/PRs

No related issues.

Suggest a fix

Case-insensitive string comparison must be used. Or alternatively, headers taken from the response must be transformed to the same format in which they will be checked for later.