[RUBY] Generator should fail if model classes shadow standard classes in the same namespace

Description

The ruby code generator should fail if one of the generated model classes shadows a standard class.

The code generator generates the model classes in the same namespace as the standard classes like for example ApiClient, ApiError, Configuration or DefaultApi. If there is a definition in the declaration file with the same name, the model class that is generated from that definition shadows the standard class. For ruby this means the model class and the standard class are mixed into one big class with unpredictable effects.

Swagger-codegen version

2.3.1

Swagger declaration file content or url

• namespace-issue-swagger-spec.yaml https://gist.github.com/cgrothaus/f3d9d4f8f4099a309fbe1a019ee70297
• codegen.json https://gist.github.com/cgrothaus/483fcaeadf64b9a978b1d8578a898e13

Command line used for generation

swagger-codegen generate -i ./namespace-issue-swagger-spec.yaml -l ruby -o ./namespace-issue/ -c ./codegen.json

Steps to reproduce

1. Generate ruby code with the command line from above
2. Have a look at the two generated files ./namespace-issue/lib/namespace_issue/api_error.rb and ./namespace-issue/lib/namespace_issue/models/api_error.rb: they both define the same class ApiError in the same module namespace.

Related issues/PRs

Nothing known to me.

Suggest a fix/enhancement

The generator should fail under such circumstances. Definitions in the swagger declaration should not be allowed to shadow standard class names.

Reproduce the issue with namespace-issue-swagger-spec.yaml, codegen.json, and the shown swagger-codegen command. Compare lib/namespace_issue/api_error.rb with lib/namespace_issue/models/api_error.rb, then verify that generation fails when both define ApiError in the same module namespace.