Support empty string OpenAPI identifiers

[simonjbeaumont]

Motivation

The OpenAPI specification allows the use of the empty string in some places, for example in the following enum, which we've seen in some real-world OpenAPI documents:

type: string
enum:
  - ""
  - foo
  - bar

We have code that converts an OpenAPI identifier to a suitable string that can be used as a Swift identifier. It currently returns an empty string when given an empty string as input, which is not a valid Swift identifier. We already have some logic there to avoid clashing with some Swift keywords, so this can be extended to handle the empty string.

Modifications

• Map the empty string OpenAPI identifier to "_empty"

Result

We can generate compiling code when presented with empty string OpenAPI identifiers.

Test Plan

• Added unit test.
• Extended reference test.

Resolves

• Resolves Empty string enum value breaks the generator #33.

[czechboy0]

🙏