[Scala] Consolidate `scala`, `async-scala`, `akka-scala` into a single Scala API client

[wing328]

Description

Similar to Java, C#, Python API clients, we want to be able to provide a single Scala API client to perform synchronous and asynchronous HTTP calls.

Swagger-codegen version

Latest master

If anyone from the community wants to work on the consolidation, please refer to let us know.

A good starting point is to review how Java API client supports both synchronous and asynchronous calls and implement the same logic in the scala or async-scala generators and templates.

[wing328]

UPDATE: scala API client in 2.3.0 now supports async request.

The next step is to update scala to use akka-http to make HTTP calls.

[wing328]

A test has been commented out due to issue mentioned in #5115 (comment)

Updating HTTP lib to use akka-http will fix it.

[foxmk]

Hello! Is there any WIP on this issue? If not, I will take it

[wing328]

@foxmk thanks for offering help on this. In the 2.3.0 branch, async-scala and scala generator has been merged into one thanks to the good work from @clasnake

If we can update scala generator in 2.3.0 to generate Scala code with the akka-http lib, that should fix the issue mentioned in #5115 (comment)

[wing328]

Here are some good starting points:

ApiInvoker mustache template for scala (2.3.0): https://github.com/swagger-api/swagger-codegen/blob/2.3.0/modules/swagger-codegen/src/main/resources/scala/apiInvoker.mustache

ApiInvoker mustache template for akka-scala (2.3.0): https://github.com/swagger-api/swagger-codegen/blob/2.3.0/modules/swagger-codegen/src/main/resources/akka-scala/apiInvoker.mustache

[foxmk]

Great! I have bunch of questions:

• If I understood correctly, we should have only one Scala client generator?
• Which project should we take as base, as they are quite different? akka-scala is Maven-only project with spray-json (now akka-http) and json4s. scala generator uses Jackson and Jersey as HTTP client. I assume It’s better to take akka-scala as base (and probably call it scala).
• Also, there is an option to write simple client generator based on akka-http from scratch :) Which is much easier and faster.
• Should we use spray-json for serialization, as it is kinda standart for akka-http projects (and faster)?
• Are there any plans to make akka-http-server generator? I can take it first to get familiar with codebase and then come back to this issue.