Does OpenAPI 3.0 allow to reference server variables? - swagger

Question

Say my OpenAPI definition has two servers. Both share the same variables. Thus I want to reference these variables to prevent duplicate code.
Actually I split my OpenAPI into files and combine it with swagger-cli bundle.
This is what it creates:
openapi: 3.0.2
info:
title: My API
description: 'some description'
version: 1.0.0
servers:
- url: 'https://stage-api.domain.com/foo/{v1}/{v2}/{v3}'
description: Staging API server for QA
variables:
v1:
description: 'variable 1'
default: 'something'
enum:
- 'foo1'
- 'foo2'
v2:
description: 'variable 2'
default: 'something'
enum:
- 'foo1'
- 'foo2'
v3:
description: 'variable 3'
default: 'something'
enum:
- 'foo1'
- 'foo2'
- url: 'https://api.domain.com/foo/{v1}/{v2}/{v3}'
description: PRODUCTION API server
variables:
region:
$ref: '#/servers/0/variables/v1'
brand:
$ref: '#/servers/0/variables/v2'
locale:
$ref: '#/servers/0/variables/v3'
paths: {}
Trying to validate this in Swagger Editor I get the following error:
Structural error at servers.1.variables.v1 should NOT have
additional properties additionalProperty: $ref Jump to line xx
Structural error at servers.1.variables.v1 should have required
property 'default' missingProperty: default Jump to line xx
Is it possible to reference the server variables or reuse them in another way?
Of course I could run swagger-cli bundle -r but I would want to prevent using that.

Answer 1

No, this is not supported. You can request changes to the OpenAPI Specification at
https://github.com/OAI/OpenAPI-Specification/issues
In your example, the server paths are almost the same except for the subdomain, so you can use a single server definition and make the subdomain a variable:
servers:
- url: 'https://{env}.domain.com/foo/{v1}/{v2}/{v3}'
variables:
env:
description: Environment - staging or production
default: stage-api
enum:
- stage-api
- api
# other variables
# ...