Referenced model with array causes NullpointerException

[samskiter]

My api spec:

swagger: '2.0'
info:
  title: Test API
  description: This is my awesome documentation
  version: 1.0.0
host: test.com

schemes:
  - https
produces:
  - application/json

paths:
  /sites:
    get:
      description: |
        Get some sites
      responses:
        '200':
          description: Success
          schema:
            $ref: '#/definitions/sites'
definitions:
  sites:
    $ref: './schemas/sitesGETresponse.schema.json'

sitesGETresponse.schema.json:

{
    "id": "sitesGETresponse.schema.json#",
    "$schema": "http://json-schema.org/draft-04/schema#",
    "title": "Site list",
    "description": "Response to site list request",
    "type": "array",
    "items": {
        "type": "string"
    }
}

Created an error:

> java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar generate -i ../path/to/my/swagger/api.yaml -o samples/client/test/android-java -l android -v
[main] INFO io.swagger.codegen.config.CodegenConfigurator -
VERBOSE MODE: ON. Additional debug options are injected
 - [debugSwagger] prints the swagger specification as interpreted by the codegen
 - [debugModels] prints models passed to the template engine
 - [debugOperations] prints operations passed to the template engine
 - [debugSupportingFiles] prints additional data passed to the template engine
reading from ../path/to/my/swagger/api.yaml
Exception in thread "main" java.lang.NullPointerException
    at io.swagger.parser.processors.ExternalRefProcessor.processRefToExternalDefinition(ExternalRefProcessor.java:63)
    at io.swagger.parser.processors.ModelProcessor.processRefModel(ModelProcessor.java:92)
    at io.swagger.parser.processors.ModelProcessor.processModel(ModelProcessor.java:33)
    at io.swagger.parser.processors.DefinitionsProcessor.processDefinitions(DefinitionsProcessor.java:40)
    at io.swagger.parser.SwaggerResolver.resolve(SwaggerResolver.java:42)
    at io.swagger.parser.SwaggerParser.read(SwaggerParser.java:64)
    at io.swagger.codegen.config.CodegenConfigurator.toClientOptInput(CodegenConfigurator.java:317)
    at io.swagger.codegen.cmd.Generate.run(Generate.java:186)
    at io.swagger.codegen.SwaggerCodegen.main(SwaggerCodegen.java:35)

Running swagger codegen built from source, master checkout

[samskiter]

More information:

I get the same error if I try to generate with objc

Note that the example works if I change sitesGETresponse.schema.json to:

{
    "id": "sitesGETresponse.schema.json#",
    "$schema": "http://json-schema.org/draft-04/schema#",
    "title": "Site list",
    "description": "Response to site list request",
    "type": "object",
    "properties": {
        "title": {
            "type": "string"
        }
    }
}

And I get another failure (this might be a different issue) with:

{
    "$ref": "./schemas/site.schema.json"
}

OR

{
    "$ref": "./site.schema.json"
}

Where site.schema.json:

{
    "id": "sitesGETresponse.schema.json#",
    "$schema": "http://json-schema.org/draft-04/schema#",
    "title": "Site",
    "description": "A site",
    "type": "object",
    "properties": {
        "title": {
            "type": "string"
        },
        "count": {
            "type": "integer"
        },
        "description": {
            "type": "string"
        }
    },
    "required": ["title"]
}

[samskiter]

I've tracked the issue to the processRefToExternalDefinition method in ExternalRefProcessor in swagger-parser. There seem to be numerous ways this one line can fail, and I've managed to find them all...

See: swagger-api/swagger-parser#132