[C++][Pistache-server] Object in a query generates code that do not compile

Description

If a query owns an object in a parameter, the generator makes code that do not compile. It seems that the corresponding method is not generated.

The compilation error looks like :

g++ -c  -I./api -I./model -I./impl -Wall -g -std=c++11 -o obj/api/CheckApi.o api/CheckApi.cpp
api/CheckApi.cpp: In member function ‘void com::bcom::amf::microservice::server::ms1::api::CheckApi::list_handler(const Pistache::Rest::Request&, Pistache::Http::ResponseWriter)’:
api/CheckApi.cpp:51:55: error: no matching function for call to ‘fromStringValue(std::__cxx11::basic_string<char>, com::bcom::amf::microservice::server::ms1::model::PresenceState&)’
         if(fromStringValue(infoClassQuery.get(), value)){
                                                       ^
In file included from api/CheckApi.cpp:14:0:
./model/Helpers.h:39:10: note: candidate: bool org::openapitools::server::helpers::fromStringValue(const string&, std::__cxx11::string&)
     bool fromStringValue(const std::string &inStr, std::string &value);

... etc

openapi-generator version

Current master : 3.3.2-SNAPSHOT

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Check generation of a structured object in the query (Pistache)
  description: Internal ref filename is check_object_in_query.yaml

servers:
  - url: http://localhost:8080
paths:
  /Check:
    get:
      summary: Check object in the query
      operationId: list
      tags:
        - Check
      parameters:
        - name: info-class
          in: query
          description: UE Context Information Class
          schema:
            $ref: '#/components/schemas/PresenceState'

      responses:
        '200':
          description: Everythings gonna be alright
          headers:
            x-next:
              description: A link to the next page of responses
              schema:
                type: string
          content:
            application/json:    
              schema:
                type: string
        default:
          description: unexpected error
          content:
            application/json:
              schema:
                type: string

components:
  schemas:

    PresenceState:
      type: object
      properties:
        prop1:
          type: string

Command line used for generation

Generate :

openapi-generator-cli.sh generate -i ./openapi.yaml -g cpp-pistache-server -c ./config.json -o .

Compile :

g++ -c  -I./api -I./model -I./impl -Wall -g -std=c++11 -o obj/api/CheckApi.o api/CheckApi.cpp

Steps to reproduce

Generate & compile

Related issues/PRs

N/A

Suggest a fix/enhancement

Each property of the query object should be considered separately, one by one, and for each of them, call the fromStringValue method to assign the corresponding member of the instantiated model.

Or

The model should implement its own 'fromStringValue" method that will assign all the values of its members from the query string.

Second suggestion is probably much more elegant. I don't know how it is solved in others languages but I trust in @etherealjoy or @stkrwork to make the best choice 👓

Start with the check_object_in_query.yaml fixture and the generated api/CheckApi.cpp and model/Helpers.h shown in the report. Run the openapi-generator-cli.sh generation command, then compile CheckApi.cpp to reproduce the failure. Done means the generated C++ Pistache server compiles and the object-valued query parameter is handled without the reported fromStringValue mismatch.