[Python] Add function to get list of allowed enum vars

Description

We have a lot of enums defined in our backend. We have a small UI that shows these enums as a dropdown. The problem we face is whenever we update the enums on our backend. We have to update the frontend code. If swagger codegen can provide the enum values as a list we can return that in an API for frontend to populate these values or use this function to render it in django forms.

For example:

Consider this class

swagger-codegen/samples/client/petstore/python/petstore_api/models/outer_enum.py

Lines 29 to 31 in b7ba962

	PLACED = "placed"
	APPROVED = "approved"
	DELIVERED = "delivered"

It has enums placed, approved, delivered. But there is no way for me to get these values as a list at the moment.

Swagger-codegen version

2.4.8

Suggest a fix/enhancement

Add a function that returns the list of enum vars.

[inf0rmatiker]

This seems to be a problem specific to reusable enums. Consider the following example:

components:
  schemas:
    Status:
      type: string
      enum:
        - PENDING
        - SUCCESS
        - FAILURE
    HardwareScan:
      type: object
      properties:
        scan_id:
          type: string
          example: 59b8915c-4e3a-49cb-b390-c0c87a15b4e1
        status:
          $ref: "#/components/schemas/Status"
        message:
          type: string

This generates a Status.py file as a Model (docstrings removed for brevity):

class Status(Model):

  PENDING = "PENDING"
  SUCCESS = "SUCCESS"
  FAILURE = "FAILURE"
  
  def __init__(self):
    self.swagger_types = {}
    self.attribute_map = {}

  @classmethod
  def from_dict(cls, dikt) -> 'Status':
    return util.deserialize_model(dikt, cls)

This Status model object gets used in HardwareScan like the following:

class HardwareScan(Model):

  # ... __init__ function, etc

  @property
  def status(self) -> Status:
    """Gets the status of this HardwareScan.

    :return: The status of this HardwareScan.
    :rtype: Status
    """
    return self._status

  @status.setter
  def status(self, status: Status):
    """Sets the status of this HardwareScan.

    :param status: The status of this HardwareScan.
    :type status: Status
    """
    self._status = status

There are no checks to make sure the correct string value is being used when setting the HardwareScan.status field. For instance, I could have used HardwareScan.status = "BOGUS_VALUE", and successfully serialized it without it even considering the value used.

This is NOT a problem when you use string enums as a part of an object's definition. For example, if we were to define:

components:
  schemas:
    HardwareScan:
      type: object
      properties:
        scan_id:
          type: string
          example: 59b8915c-4e3a-49cb-b390-c0c87a15b4e1
        status:
          type: string
          enum:
            - PENDING
            - SUCCESS
            - FAILURE
        message:
          type: string

This would set the HardwareScan.status field to type str, and a setter field with:

  @status.setter
  def status(self, status: str):
    """Sets the status of this HardwareAdd.
  
    :param status: The status of this HardwareAdd.
    :type status: str
    :type status: Status
    """
    allowed_values = ["PENDING", "FAILURE", "SUCCESS"]
      if status not in allowed_values:
        raise ValueError(
          "Invalid value for `status` ({0}), must be one of {1}"
          .format(status, allowed_values)
    
    self._status = status

And any attempts to set the field with an incorrect string would raise a ValueError exception.
Perhaps we could look into using Python 3 Enum and StrEnum as potential candidates for reusable enum objects?