[Bug, python-legacy] Generate list of reference is generated as an object instead of list[Pet] with OpenAPI 3.1.0

[GuillaumeSmaha]

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?
• [] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The response for findByStatus is generated as a object instead of a list.

openapi-generator version

6.2.1 or master branch

OpenAPI declaration file content or url

Based on https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/3_0/petstore_oas3_test.yaml and updating the OpenAPI version to 3.1.0 (removing license to be compatible)

openapi: 3.1.0
servers:
  - url: 'http://petstore.swagger.io/v2'
info:
  description: >-
    A test spec based on the Petstore spec with OAS3 related test cases such as nullable
  version: 1.0.0
  title: OpenAPI Petstore
tags:
  - name: pet
    description: Everything about your Pets
  - name: store
    description: Access to Petstore orders
  - name: user
    description: Operations about user
paths:
  /pet/findByStatus:
    get:
      tags:
        - pet
      summary: Finds Pets by status
      description: Multiple status values can be provided with comma separated strings
      operationId: findPetsByStatus
      parameters:
        - name: status
          in: query
          description: Status values that need to be considered for filter
          required: true
          style: form
          explode: false
          schema:
            type: array
            items:
              type: string
              enum:
                - available
                - pending
                - sold
              default: available
      responses:
        '200':
          description: successful operation
          content:
            application/xml:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Pet'
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Pet'
        '400':
          description: Invalid status value
      security:
        - petstore_auth:
            - 'write:pets'
            - 'read:pets'
components:
  schemas:
    Category:
      title: Pet category
      description: A category for a pet
      type: object
      properties:
        id:
          type: integer
          format: int64
        name:
          type: string
      xml:
        name: Category
    User:
      title: a User
      description: A User who is purchasing from the pet store
      type: object
      properties:
        id:
          type: integer
          format: int64
        username:
          type: string
        firstName:
          type: string
        lastName:
          type: string
        email:
          type: string
        password:
          type: string
        phone:
          type: string
        userStatus:
          type: integer
          format: int32
          description: User Status
      xml:
        name: User
    Tag:
      title: Pet Tag
      description: A tag for a pet
      type: object
      properties:
        id:
          type: integer
          format: int64
        name:
          type: string
      xml:
        name: Tag
    Pet:
      title: a Pet
      description: A pet for sale in the pet store
      type: object
      required:
        - name
        - photoUrls
      properties:
        id:
          type: integer
          format: int64
        category:
          $ref: '#/components/schemas/Category'
        name:
          type: string
          example: doggie
        photoUrls:
          type: array
          xml:
            name: photoUrl
            wrapped: true
          items:
            type: string
        tags:
          type: array
          xml:
            name: tag
            wrapped: true
          items:
            $ref: '#/components/schemas/Tag'
        status:
          type: string
          description: pet status in the store
          enum:
            - available
            - pending
            - sold
      xml:
        name: Pet

Steps to reproduce

docker run --rm -u $(id -u):$(id -g) -v $(pwd):/local -w /local \
                         openapitools/openapi-generator-cli:latest generate \
                  -i petstore_oas3.1_test.yaml \
                  -o python-client \
                  -g python-legacy

Result expected

For example, using python-legacy generator, I get:

        response_types_map = {
            200: "object",
            400: None,
        }

instead of a list of Pet with OpenAPI: 3.0.x:

        response_types_map = {
            200: "list[Pet]",
            400: None,
        }

[GuillaumeSmaha]

I also got the same result when I created a specific schema for Pets:

    Pets:
      type: array
      items:
        $ref: '#/components/schemas/Pet'

and use it as response schemas:

      responses:
        '200':
          description: successful operation
          content:
            application/xml:
              schema:
                $ref: '#/components/schemas/Pets'
            application/json:
              schema:
                $ref: '#/components/schemas/Pets'

it seems really linked to the array format

[GuillaumeSmaha]

I made a test to validate the issue in DefautlCodegenTest.java:

    @Test
    public void test310ResponsesArray() {
        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_1/petstore.yaml");
        final DefaultCodegen codegen = new DefaultCodegen();
        codegen.setOpenAPI(openAPI);

        final String path = "/pet/findByStatus";

        final Operation operation = openAPI.getPaths().get(path).getGet();
        final CodegenOperation co = codegen.fromOperation(path, "get", operation, null);

        Assert.assertTrue(co.responses.get(0).isArray);
    }

I can see the difference with:

    @Test
    public void test300ResponsesArray() {
        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/petstore.yaml");
        final DefaultCodegen codegen = new DefaultCodegen();
        codegen.setOpenAPI(openAPI);

        final String path = "/pet/findByStatus";

        final Operation operation = openAPI.getPaths().get(path).getGet();
        final CodegenOperation co = codegen.fromOperation(path, "get", operation, null);

        System.err.println("test300ResponsesArray");
        System.err.println("dataType: " + co.responses.get(0).dataType);
        System.err.println("baseType: " + co.responses.get(0).baseType);
        System.err.println("containerType: " + co.responses.get(0).containerType);
        System.err.println("jsonSchema: " + co.responses.get(0).jsonSchema);
        Assert.assertTrue(co.responses.get(0).isArray);
        Assert.assertEquals("10", "100");
    }

    @Test
    public void test310ResponsesArray() {
        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_1/petstore.yaml");
        final DefaultCodegen codegen = new DefaultCodegen();
        codegen.setOpenAPI(openAPI);

        final String path = "/pet/findByStatus";

        final Operation operation = openAPI.getPaths().get(path).getGet();
        final CodegenOperation co = codegen.fromOperation(path, "get", operation, null);

        System.err.println("test310ResponsesArray");
        System.err.println("dataType: " + co.responses.get(0).dataType);
        System.err.println("baseType: " + co.responses.get(0).baseType);
        System.err.println("containerType: " + co.responses.get(0).containerType);
        System.err.println("jsonSchema: " + co.responses.get(0).jsonSchema);
        Assert.assertTrue(co.responses.get(0).isArray);
        Assert.assertEquals("20", "200");
    }

Here the output:

test300ResponsesArray
dataType: List
baseType: Pet
containerType: array
jsonSchema: {
  "description" : "successful operation",
  "content" : {
    "application/xml" : {
      "schema" : {
        "type" : "array",
        "items" : {
          "$ref" : "#/components/schemas/Pet"
        }
      }
    },
    "application/json" : {
      "schema" : {
        "type" : "array",
        "items" : {
          "$ref" : "#/components/schemas/Pet"
        }
      }
    }
  }
}
test310ResponsesArray
dataType: oas_any_type_not_mapped
baseType: AnyType
containerType: null
jsonSchema: {
  "description" : "successful operation",
  "content" : {
    "application/xml" : {
      "schema" : {
        "items" : {
          "$ref" : "#/components/schemas/Pet"
        }
      }
    },
    "application/json" : {
      "schema" : {
        "items" : {
          "$ref" : "#/components/schemas/Pet"
        }
      }
    }
  }
}

[GuillaumeSmaha]

With ./run-in-docker.sh mvn test -Dtest='*#test310ResponsesArray' | tee log, I got a AnyType result on line:

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

Line 2433 in 31c3a40

LOGGER.warn("Unknown type found in the schema: {}. To map it, please use the schema mapping option (e.g. --schema-mappings in CLI)", schema.getType());

Since swagger-models 2.2.x, the schema is a JsonSchema with types (not type) defined as [array]:
https://github.com/swagger-api/swagger-parser/blob/v2.1.11/modules/swagger-parser-v3/src/main/java/io/swagger/v3/parser/util/ResolverFully.java#L383-L390

class JsonSchema {
    class Schema {
        type: [array]
        format: null
        $ref: null
        description: null
        title: null
        multipleOf: null
        maximum: null
        exclusiveMaximum: null
        minimum: null
        exclusiveMinimum: null
        maxLength: null
        minLength: null
        pattern: null
        maxItems: null
        minItems: null
        uniqueItems: null
        maxProperties: null
        minProperties: null
        required: null
        not: null
        properties: null
        additionalProperties: null
        nullable: null
        readOnly: null
        writeOnly: null
        example: null
        externalDocs: null
        deprecated: null
        discriminator: null
        xml: null
        patternProperties: null
        contains: null
        $id: null
        $anchor: null
        $schema: null
        const: null
        contentEncoding: null
        contentMediaType: null
        contentSchema: null
        propertyNames: null
        unevaluatedProperties: null
        maxContains: null
        minContains: null
        additionalItems: null
        unevaluatedItems: null
        _if: null
        _else: null
        then: null
        dependentRequired: null
        dependentSchemas: null
        $comment: null
        prefixItems: null
    }
}

[spacether]

FYI our project does not yet work with openapi 3.1.0 specs. There is a warning in the terminal about it when they are ingested.
See #9083 to track 3.1.0 feature work