[Any] Code generation fails when using parameter in another file

[rwf-hcl]

Description

When referencing a parameter defined in another file, the swagger-editor successfully validates the YAML and creates the API documentation, but code generation fails with a NullPointer exception and no further details. If the same parameter is defined in the parameters section of the single file, then everything is ok.

Any code generation fails. I specifically tried server-JAX-RS and client-HTML.

Swagger-codegen version

swagger-editor 2.10.3
swagger-codegen 2.2.2

Swagger declaration file content or url

-- main yaml file ---------------------------

swagger: "2.0"

info:
  title: Test Case for Code Gen Issue - Fails
  description: |
    Test case to demonstrate the problem with generating code when external parameter references are used.
    This is the failure test case.
  version: 0.0.1

produces:
  - application/json

paths:

  /test/fails:

    get:
      parameters:
        - $ref: 'fails_param.yaml#/parameters/TheParam'
      responses:
        "200":
          $ref: '#/responses/TheResponse'

parameters: {} # are in fails_param.yaml


responses:

  TheResponse:
    description: The response.
    schema:
      $ref: '#/definitions/TheResponseSchema'

definitions:

  TheResponseSchema:
    description: The response schema.
    type: object
    properties:
      prop1:
        type: integer
      prop2:
        type: string

# end

-- included file (params) ------------------

# parameters used in fails_main.yaml

swagger: "2.0"

info:
  title: Parameters for Test Case for Code Gen Issue - Fails
  description: |
    Parameters for the test case to demonstrate the problem with generating 
    code when external parameter references are used.
    This is the failure test case.
  version: 0.0.1

parameters:

  TheParam:
    name: param
    in: query
    type: string
    description: The parameter.
# end

-- end YAML files --------------------------------

Command line used for generation

Initially done from swagger-editor (local)

java -jar C:\Utils\swagger-tools\swagger-codegen-cli.jar generate -l jaxrs -i fails_main.yaml

Steps to reproduce

Use above swagger-codegen-cli command in a directory with both the above YAML files.

Exception reported by swagger-codegen-cli

Exception in thread "main" java.lang.NullPointerException
        at io.swagger.codegen.DefaultGenerator.generateParameterId(DefaultGenerator.java:834)
        at io.swagger.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:758)
        at io.swagger.codegen.DefaultGenerator.processPaths(DefaultGenerator.java:727)
        at io.swagger.codegen.DefaultGenerator.generateApis(DefaultGenerator.java:356)
        at io.swagger.codegen.DefaultGenerator.generate(DefaultGenerator.java:666)
        at io.swagger.codegen.cmd.Generate.run(Generate.java:234)
        at io.swagger.codegen.SwaggerCodegen.main(SwaggerCodegen.java:41)

The problem seems to be that the $ref in the parameters section is not properly parsed. In the verbose mode, it shows a null parameter list.

  "paths" : {
    "/test/fails" : {
      "get" : {
        "parameters" : [ null ],
        "responses" : {
          "200" : {
            "description" : "The response.",
            "schema" : {
              "$ref" : "#/definitions/TheResponseSchema"
            }
          }
        }
      }
    }
  },

Related issues

Suggest a Fix

[rwf-hcl]

Update: When prefixing the referenced file with "./" codgen works when using the CLI. But it still fails from the editor (same way).
It should not be necessary to use the "./" prefix, and it works without the prefix for definitions.

[wing328]

@RWFischer The behaviour is determined by Swagger Parser and here is the PR to enhance it: swagger-api/swagger-parser#422