[BUG][C#] Should use nullable types for non-required properties
Created by: kevinoid
Bug Report Checklist
-
Have you provided a full/minimal spec to reproduce the issue? -
Have you validated the input using an OpenAPI validator (example)? -
What's the version of OpenAPI Generator used? -
Have you search for related issues/PRs? -
What's the actual output vs expected output? -
[Optional] Bounty to sponsor the fix (example)
Description
The C# generators currently generate model classes using non-nullable types for properties which are not required, which can't represent instances where those properties are not present.
openapi-generator version
v4.0.0 and later
OpenAPI declaration file content or url
Example OpenAPI 3.0.2 document
openapi: '3.0.2'
info:
title: non-required property example
version: '1.0.0'
components:
schemas:
DateRange:
description: A possibly open-ended date range.
type: object
properties:
start:
type: string
format: date-time
end:
type: string
format: date-time
required:
- start
paths:
/date-ranges:
get:
operationId: getDateRanges
responses:
default:
description: Get date ranges
content:
application/json:
schema:
type: array
items:
$ref: '#/components/schemas/DateRange'
post:
operationId: addDateRange
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/DateRange'
responses:
'201':
description: Success
Note that end
is not declared nullable: true
because end
is never null
in the JSON produced or consumed by the API. It is either a date string, or not present.
Command line used for generation
java -jar openapi-generator-cli.jar generate -g csharp-netcore -i openapi.yaml -o generated
Steps to reproduce
- Ensure the API returns at least one open-ended range (i.e. a
DateRange
object without anend
property). - Call
GetDateRanges
and note thatEnd
for the open-ended range isDateTime(1900-01-01)
, which is problematic since it is indistinguishable from"end":"1900-01-01"
and likely violates the constraint thatEnd
is not beforeStart
. - Note that there is no way to call
AddDateRange
with an open-ended range, sinceEnd
will always have a value.
Related issues/PRs
The regression occurred between v3.0.2 and v4.0.0. Bisect says the first bad commit is 37442733 (v4.0.0
), so I'm obviously doing something wrong. (Maybe cli
is using published core
of same version, rather than locally-built version?) Advice on how to bisect would be appreciated.
The issue was also discussed in https://github.com/OpenAPITools/openapi-generator/issues/3725#issuecomment-545039145.
Suggest a fix
I believe nullable types should be used for properties which are either nullable
or not required
, since null
in C# is a reasonable representation of both JSON properties which are null
and properties which are not present.
Thanks for considering, Kevin