[C++][Pistache] Fixed #2643

[SalDiAngelus]

Refactored to/from json functions to use universal object serialization method.

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@ravinikam, @stkrwork, @fvarose, @etherealjoy, @MartinDelille

Description of the PR

Purpose is to fix issue #2643. While I was in there, I saw the mustache file for serialization was more complex than it needed to be so I simplified it by using the to_json and from_json functions that nlohmann/json uses to find custom types to serialize. Removed the ModelBase class because the helper functions weren't needed anymore.

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[SalDiAngelus]

@stkrwork Can I ask what the purpose of the helpers class is? It doesn't seems to be used for anything in generated APIs.

[stkrwork]

Their purpose was to convert strings, or array in string to the correct datatype. with your new system, they should be redundant as well now.

[SalDiAngelus]

Should I delete it then?

[stkrwork]

if they aren't referenced anywhere in the code, yes

[stkrwork]

@etherealjoy as you made the helpers, can you check this as well?

[etherealjoy]

@SalDiAngelus
I will try this PR with nested arrays/maps.
Did you try a spec with nested arrays and maps by any chance

[etherealjoy]

Code does not compile anymore
https://github.com/OpenAPITools/openapi-generator/pull/2653/files#diff-d3400a21fe4566d943fead7d6a483aebL90

PetApi.cpp: In member function ‘void 
org::openapitools::server::api::PetApi::find_pets_by_status_handler(const Pistache::Rest::Request&, 
Pistache::Http::ResponseWriter)’:
PetApi.cpp:85:12: error: ‘fromStringValue’ was not declared in this scope
         if(fromStringValue(statusQuery.get(), value)){

[SalDiAngelus]

I've tried nested arrays with non default types, but I haven't used maps.

[etherealjoy]

ok, it compiles now
I will test it with nested maps

[etherealjoy]

I used this spec

---
# This is a sample Swagger spec, describing a simple API as a starting point.
swagger: "2.0"
info:
  description: Template Description
  version: 1.0.0
  title: Testspec


host: 0.0.0.0:8080
basePath: /api
schemes:
- http

paths:
  /v1.0/test0:
    get:
      description: ""
      operationId: test0
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/obj'
        400:
          description: "The request was not successfully executed."

  /v1.0/test1:
    get:
      description: ""
      operationId: test1
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/arrofarr'
        400:
          description: "The request was not successfully executed."
     
  /v1.0/test2:
    get:
      description: ""
      operationId: test2
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/mapofmap'
        400:
          description: "The request was not successfully executed."

  /v1.0/test3:
    get:
      description: ""
      operationId: test3
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/arrofmap'
        400:
          description: "The request was not successfully executed."
     
  /v1.0/test4:
    get:
      description: ""
      operationId: test4
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/mapofarr'
        400:
          description: "The request was not successfully executed."      
  /v1.0/test5:
    get:
      description: ""
      operationId: test5
      responses:
        200:
          description: "Successful response"
          schema:
            $ref: '#/definitions/cplxobj'
        400:
          description: "The request was not successfully executed."            

definitions:

  obj:
    description: "simple object"
    type: object
    properties:
      simpleitem:
        type: string

  arrofarr:
    description: "array of array"
    type: array
    items:
      type: array
      items: 
        $ref: '#/definitions/obj'

  mapofmap:
    description: "map of map"
    type: object
    additionalProperties:
      type: object
      additionalProperties:
        $ref: '#/definitions/obj'

  arrofmap:
    description: "array of map"
    type: array
    items:
      type: object
      additionalProperties:
        $ref: '#/definitions/obj'

  mapofarr:
    description: "map of array"
    type: object
    additionalProperties:
      type: array
      items: 
        $ref: '#/definitions/obj' 
        
  cplxobj:
    description: "complex object"
    type: object
    properties:
      item1:
        $ref: '#/definitions/arrofarr'  
      item2:
        $ref: '#/definitions/mapofmap'  
      item3:
        $ref: '#/definitions/arrofmap'  
      item4:
        $ref: '#/definitions/mapofarr'          

[etherealjoy]

This is up for discussion, but the deserialiation of array and map aliases is a little more complicated due to missing helpers.

Just for discussion i dont have preferences.

[SalDiAngelus]

This is up for discussion, but the deserialiation of array and map aliases is a little more complicated due to missing helpers.

Just for discussion i dont have preferences.

Nlohmann json had std container types built in. Using the yaml file you provided, the code below generates the json below.

Cplxobj obj;
Obj obj2;
obj2.setSimpleitem("value");
obj.m_Item1IsSet = true;
obj.m_Item2IsSet = true;
obj.m_Item3IsSet = true;
obj.m_Item4IsSet = true;
obj.m_Item1 = { {obj2,obj2}, {obj2, obj2, obj2} };
obj.m_Item2 = { {"a", {{"1", obj2}, {"2", obj2}}}, {"b", { { { "3", obj2 }, {"4", obj2}, {"5", obj2} } }} };
obj.m_Item3 = { {{"1", obj2}, {"2", obj2}}, { {"3", obj2}, {"4", obj2}, {"5", obj2}} };
obj.m_Item4 = { {"a", {obj2,obj2} }, {"b", {obj2, obj2, obj2}} };
string str = nlohmann::json(obj).dump();

{
  "item1":[
    [
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      }
    ],
    [
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      }
    ]
  ],
  "item2":{
    "a":{
      "1":{
        "simpleitem":"value"
      },
      "2":{
        "simpleitem":"value"
      }
    },
    "b":{
      "3":{
        "simpleitem":"value"
      },
      "4":{
        "simpleitem":"value"
      },
      "5":{
        "simpleitem":"value"
      }
    }
  },
  "item3":[
    {
      "1":{
        "simpleitem":"value"
      },
      "2":{
        "simpleitem":"value"
      }
    },
    {
      "3":{
        "simpleitem":"value"
      },
      "4":{
        "simpleitem":"value"
      },
      "5":{
        "simpleitem":"value"
      }
    }
  ],
  "item4":{
    "a":[
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      }
    ],
    "b":[
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      },
      {
        "simpleitem":"value"
      }
    ]
  }
}

[etherealjoy]

Ok, good.
One improvement we can do in the future is somethign like the Qt5 Server it create handler with correct signature directly
Or at least create a local objects which are deserialized from the request for the steps you mentioned above