[C#] Required enum values are not serialized

[kbedel]

Description

Using the default options, the client does not serialize enum properties if they are the default enum value. If the property is marked as required, this means that the resulting JSON does not actually satisfy the specification.

This only occurs for enums which are defined as their own object. If the enum is defined inline, the property is generated as MyEnumType?, but for the ones defined as top level definitions, it is just MyEnumType

Setting the -DoptionalEmitDefaultValues=true parameter will change this, but will affect all properties.

Swagger-codegen version

2.2.3

Swagger declaration file content or url

swagger: "2.0"
info:
  description: "This is a sample server Petstore server.  You can find out more about     Swagger at [http://swagger.io](http://swagger.io) or on [irc.freenode.net, #swagger](http://swagger.io/irc/).      For this sample, you can use the api key `special-key` to test the authorization     filters."
  version: "1.0.0"
  title: "Swagger Petstore"
  termsOfService: "http://swagger.io/terms/"
  contact:
    email: "apiteam@swagger.io"
  license:
    name: "Apache 2.0"
    url: "http://www.apache.org/licenses/LICENSE-2.0.html"
host: "petstore.swagger.io"
basePath: "/v2"
tags:
- name: "pet"
  description: "Everything about your Pets"
  externalDocs:
    description: "Find out more"
    url: "http://swagger.io"
- name: "store"
  description: "Access to Petstore orders"
- name: "user"
  description: "Operations about user"
  externalDocs:
    description: "Find out more about our store"
    url: "http://swagger.io"
schemes:
- "http"
paths:
  /pet:
    post:
      tags:
      - "pet"
      summary: "Add a new pet to the store"
      description: ""
      operationId: "addPet"
      consumes:
      - "application/json"
      - "application/xml"
      produces:
      - "application/xml"
      - "application/json"
      parameters:
      - in: "body"
        name: "body"
        description: "Pet object that needs to be added to the store"
        required: true
        schema:
          $ref: "#/definitions/Pet"
      responses:
        405:
          description: "Invalid input"
definitions:
  PetStatus:
    type: "string"
    description: "pet status in the store"
    enum:
    - "available"
    - "pending"
    - "sold"
  Pet:
    type: "object"
    required:
    - "name"
    - "status"
    properties:
      name:
        type: "string"
        example: "doggie"
      status:
        $ref: "#/definitions/PetStatus"

Command line used for generation

java -jar swagger-codegen-cli-2.2.3.jar generate -i ./swagger.json -l csharp
where swagger.json is the result of downloading the JSON file from the online swagger editor for the above YAML

Steps to reproduce

1. Generate the client

2. Run the following code snippet against the generated code:

   new Pet("Kitty McKittyface", PetStatus.Available).ToJson();

   The result will be missing the status:

   {
     "name": "Kitty McKittyface"
   }

3. Alternately, the following serializes correctly since the PetStatus value is not the default:

   new Pet("Kitty McKittyface", PetStatus.Sold).ToJson();

Related issues/PRs

#4262 is somewhat related, but doesn't cover this exact scenario

Suggest a fix/enhancement

From looking through the other issues, it seems like Nullable types for required properties is a bit of a sticking point, so would it make sense to ignore the optionalEmitDefaultValues argument for required parameters (even beyond enums?) and also set EmitDefaultValue=true for required properties?

[kbedel]

Changing the definitions section in the YAML to

definitions:
  Pet:
    type: "object"
    required:
    - "name"
    - "status"
    properties:
      name:
        type: "string"
        example: "doggie"
      status:
        type: "string"
        description: "pet status in the store"
        enum:
        - "available"
        - "pending"
        - "sold"

will show the case where the output uses a Nullable type

[jimschubert]

@kbedel You have two issues reported here. For the first issue, with properties referencing standalone enum models, this should be fixed in #6851.

For the second issue, where Pet.Available isn't serialized, this is because of the EmitDefaultValue=false annotation on the properties. I believe this is what we'll want in almost every case, however string enums by their nature have no default value (or the first value should be a placeholder by convention).

I've opened #6873 for feedback on this, which out of necessity of the standalone enums the PR also includes work from #6851.

[kbedel]

@jimschubert Great, I tested this with the latest 2.3.0-SNAPSHOT build and everything looks good to me. Thanks for resolving this. Do you want me to close the issue?

[jimschubert]

Awesome! You could go ahead and close it if master works. If you encounter any other issues, please open a new issue.