[BUG][Python] Stackoverflow error when using required recursive properties

[vincent-raman]

Description

If we want to define a recursive type (like a tree), the client generation for python crashes with a StackOverflowError in the PythonClientCodegen.toExampleValueRecursive method.

openapi-generator version

4.3.1

OpenAPI declaration file content or url

{
  "openapi": "3.0.0",
  "info": {
    "version": "1.0.0",
    "title": "Test swagger file"
  },
  "paths": {
    "/tree": {
      "post": {
        "description": "Create",
        "operationId": "createTree",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/Tree"
              }
            }
          },
          "description": "The tree to create",
          "required": true
        },
        "tags": [
          "Test"
        ],
        "responses": {
          "200": {
            "description": "Successfully created the tree",
            "content": {
              "*/*": {
                "schema": {
                  "$ref": "#/components/schemas/Tree"
                }
              }
            }
          },
          "400": {
            "description": "Bad request"
          }
        }
      },
    }
  },
  "components": {
    "schemas": {
      "Tree": {
        "type": "object",
        "required": [
          "id",
          "name",
          "children"
        ],
        "properties": {
          "id": {
            "type": "integer"
          },
          "name": {
            "type": "string"
          },
          "description": {
            "type": "string"
          },
          "children": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/Tree"
            }
          }
        }
      }
    }
  }
}

Generation Details

Generation of a client with language "python" and this schema definition

Steps to reproduce

Try to generate a python client

Suggest a fix

In the method PythonClientCodegen.toExampleValueRecursive, when treating an object (if (ModelUtils.isObjectSchema(schema)), the already treated properties are removed.

for (String toRemove : included_schemas) {
    if (reqs.contains(toRemove)) {
        reqs.remove(toRemove);
    }
}

But, just after, the "required" properties are added back, making this safeguard useless

if (null != schema.getRequired()) for (Object toAdd : schema.getRequired()) {
    reqs.add((String) toAdd);
}

[delenius]

I was just about to file a report for the same issue. It is still there in the latest master as of writing this (now at 5.1.0-SNAPSHOT).

Here is a repo to easily reproduce, in case it helps.

Note: The suggested validator in the issue filing system complains about the recursive type, but e.g. the Swagger online editor does not. In any case, clearly one has to be allowed to have recursive types for trees etc.

@vincent-raman, could you file a PR, since you found a fix? Otherwise, I might take a crack at it

[eak24]

Also fails in python-experimental

[spacether]

The above PR fixes the java layer of python clients
Similar PRs may be needed to prevent infinite recursion in python clients

[RichiCoder1]

I still appear to be getting this error (or at least one very similiar to it) when using python-experimental and https://instana.github.io/openapi/openapi.yaml

[vincent-raman]

It seems fixed in python-prior (renamed from python) in v6.2.0