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?

Description

I would like to use additionalProperties in the OpenAPI definition in order to allow accepting responses in the following JSON payload format (Array of maps with string as map key and a fixed typed object as map value. It would make my job easier if it wouldn't be in an array format, but I have to work with this type definition in a company environment. Namings are already altered to avoid sensitive info.):

[
  {
    "key property 1": {
      "id": 1,
      "name": "value 1"
    },
    "key property 2": {
      "id": 2,
      "name": "value 2"
    },
    "key property 3": {
      "id": 3,
      "name": "value 3"
    }
  }
]

In a generated Go client, the return type results in the following, which is the expected in Go:

// api_example.go
[]map[string]NestedSchema

However, I have to write a C++ client, and cpprest-sdk generator on the other hand generates the following type in the function signature:

// api/ExampleApi.h
pplx::task<std::vector<std::shared_ptr<std::map>>> getMapWithNestedSchema() const;

The generated ExampleApi.h and ExampleApi.cpp files do not compile, because std::map lacks the template parameters for the key and value type. Expected output is the following:

// api/ExampleApi.h
pplx::task<std::vector<std::shared_ptr<std::map<utility::string_t, std::shared_ptr<NestedSchema>>>>> getMapWithNestedSchema() const;

openapi-generator version

v6.0.0

OpenAPI declaration file content or url

swagger: '2.0'
info:
  title: Example to reproduce API generation with complex map type
  version: 0.0.0
basePath: /api/v1

schemes:
  - http
consumes:
  - application/json
produces:
  - application/json

tags:
  - name: example

paths:
  '/mapWithNestedSchema':
    get:
      operationId: 'GetMapWithNestedSchema'
      tags:
        - example
      responses:
        200:
          description: OK
          schema:
            type: 'array'
            items:
              $ref: '#/definitions/MapWithNestedSchema'
        500:
          description: Error

definitions:
  MapWithNestedSchema:
    type: 'object'
    description: 'A map with arbitrary string as key and object as value'
    additionalProperties: 
      $ref: '#/definitions/NestedSchema'
    example:
      'key property 1':
        id: 1
        name: 'value 1'
      'key property 2':
        id: 2
        name: 'value 2'
      'key property 3':
        id: 3
        name: 'value 3'
  
  NestedSchema:
    type: 'object'
    properties: 
      id:
        type: 'number'
        example: 1
      name:
        type: 'string'
        example: 'value 1'

Generation Details

generatorName: cpp-restsdk
outputDir: myclient
inputSpec: swagger.yaml

Steps to reproduce

1. Run v6.0.0 version of openapi-codegen-cli with swagger.yml in the root folder. I used the dockerized execution.

docker run --rm -v "${PWD}:/local" --user "$(shell id -u):$(shell id -g)" openapitools/openapi-generator-cli:v6.0.0 generate \
    -i /local/swagger.yml \
    -g cpp-restsdk \
    -o /local/myclient

Also tried openapitools/openapi-generator-cli:latest too, but result was the same. Tried manually building from master with ./mvnw clean install, but the 6.0.1-SNAPSHOT build failed.

cd myclient
mkdir build
cd build
cmake ..
make

Related issues/PRs

#5148
#5222

Suggest a fix

As a workaround, I currently preprocess my swagger.yml file with sed to change the path to return "typeless items" and use them in code that way.

paths:
  '/mapWithNestedSchema':
    get:
      operationId: 'GetMapWithNestedSchema'
      tags:
        - example
      responses:
        200:
          description: OK
          schema:
            type: 'array'
            items:
              {}   # sed -i 's/$ref: '\''#\/definitions\/MapWithNestedSchema'\''/{}/g' swagger.yml 
        500:
          description: Error

// api/ExampleApi.h
pplx::task<std::vector<std::shared_ptr<Object>>> getMapWithNestedSchema() const;

swagger-codegen-cli:2.4.27 is already able to recognize an array of MapWithNestedSchema types, but has other troubles of generating MapWithNestedSchema as an std::map.

// api/ExampleApi.h
pplx::task<std::vector<std::shared_ptr<MapWithNestedSchema>>> getMapWithNestedSchema();

// models/MapWithNestedSchema.h
class  MapWithNestedSchema
    : public null<String, NestedSchema>
{
  ...
}

I tried copying the existing .mustache file templates for the API header and source and modifying them as a workaround, but so far I was only able to use the {#isMap} directive on request parameter types ({#allParams} -> {dataType}). If there would be a way to specify my custom .mustache file to check for map type or nested type in the result, that would be helpful. On the other hand, I would also appreciate help on how to improve the existing .yml file.