[BUG][Python] Stringified Enum variable used in request path instead of underlying string

[john-odonnell]

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

When an Enum of strings is used as a path parameter, the request path contains a stringified constant variable name instead of the underlying string.

openapi-generator version

openapitools/openapi-generator-cli:latest

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: ""
  version: ""
paths:
  /items/{enumParam}:
    get:
      parameters:
      - name: enumParam
        in: path
        required: true
        schema:
          $ref: "#/components/schemas/EnumValue"
      responses:
        200:
            description: "Responds with the requested path"
            content:
              text/plain:
                schema:
                  type: string
components:
  schemas:
    EnumValue:
      type: string
      enum:
        - a
        - b

Generation Details

Generating using the Python client generator with default settings.

# ${PWD}/config.yml
generatorName: python
outputDir: /spec/python
inputSpec: /spec/openapi.yml

docker run --rm \
  -v "${PWD}":/spec \
  openapitools/openpai-generator-cli:latest \
    generate -c /spec/config.yml

Steps to reproduce

1. Start a local web server that responds to requests with the requested resource path.

   # ${PWD}/echo_server.py
   import http.server
   import socketserver
   
   port = 80
   
   # Create a custom request handler that responds to all requests
   class CustomHandler(http.server.SimpleHTTPRequestHandler):
       def do_GET(self):
           # Extract the requested API path
           api_path = self.path
           self.send_response(200)
           self.send_header('Content-type', 'text/html')
           self.end_headers()
           self.wfile.write(api_path.encode('utf-8'))
   
   # Create a socket server with the custom request handler
   with socketserver.TCPServer(('', port), CustomHandler) as httpd:
       print(f"Server running on port {port}")
       # Start the server
       httpd.serve_forever()

   $ python3 echo_server.py
   Server running on port 80
   

2. Install the generated client:

   $ cd python
   $ python3 setup.py install --user
   

   This creates an EnumValue model:

   class EnumValue(str, Enum):
       """
       EnumValue
       """
   
       """
       allowed enum values
       """
       A = 'a'
       B = 'b'
   
       @classmethod
       def from_json(cls, json_str: str) -> EnumValue:
           """Create an instance of EnumValue from a JSON string"""
           return EnumValue(json.loads(json_str))

3. Make requests to an endpoint that uses an Enum type as a path parameter:

   # #{PWD}/example.py
   import openapi_client
   from openapi_client.models import EnumValue
   
   configuration = openapi_client.Configuration(host = "http://localhost")
   
   with openapi_client.ApiClient(configuration) as api_client:
       api_instance = openapi_client.DefaultApi(api_client)
   
       print(api_instance.items_enum_param_get(EnumValue.A))
       print(api_instance.items_enum_param_get(EnumValue.A.value))
       print(api_instance.items_enum_param_get('a'))

   This code outputs the following:

   $ python3 example.py
   /items/EnumValue.A
   /items/EnumValue.A
   /items/EnumValue.A
   

   I expect it to output:

   $ python3 example.py
   /items/a
   /items/a
   /items/a
   

Related issues/PRs

I don't think there is an open issue that matches this one.

Suggest a fix

As a workaround in my own project, I updated api_client.mustache to check if path parameters are instances of aenum.Enum and dereference them:

for k, v in path_params:
+   # dereference Enums
+   if isinstance(v, Enum)
+       v = v.value
+
    # specified safe chars, encode everything
    resource_path = resource_path.replace(
        '{%s}' % k,
        quote(str(v), safe=config.safe_chars_for_path_param)
    )

Would probably need to do the same for query parameters, too.

[wing328]

@john-odonnell thanks for reporting the issue. What about applying a fix similar to https://github.com/OpenAPITools/openapi-generator/pull/15278/files#diff-18c932643600d7fe7b3ae94dcf8f006187cdae3e1714269eba37fe5b7c523ffdR202 to the path parameters?