[REQ][dart] Dart full OAS3 support

[kuhnroyal]

This is an epic to track remaining work for full dart/dart-dio OAS3 support.

General:

• OAS3 fake petstore contains a model called File. This is generated as a separate model in the Go client but as java.io.File in Java/Kotlin. It should probably be a separate model. Currently this leads to compile errors. (addressed by [dart][dart-dio] Prevent name clashes with existing dart types #8198)

Dart:

• There are problems regarding deserialization of maps, de-serialization code is trying to call Map.mapFromJson. There are open issues for this and the problem is now evident in the generated fake petstore.
  Related issues: [BUG][Dart] Map.mapFromJson is generated, but there's no such method on map. #8029
• De-serialization of maps of maps e.g. Map<String, Map<String, String>>
• De-serialization of maps of enums e.g. Map<String, Enum>
• De-serialization of list of list of model e.g. List<List<ReadOnlyFirst>>
• Support enums of type double, de-serialization via switch statement doesn't work here
• De-serialization of List<Object> tries to call Object.mapFromJson
• OAS3 fake petstore contains a model called Client, this conflict with http.Client (addressed by [dart][dart-dio] Prevent name clashes with existing dart types #8198)

Dart-Dio:

• Compile errors regarding header parameters of type bool and List, basically everything that is not a String (addressed by [dart-dio] Allow dynamic headers and add additional dio parameters #8191)

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[kuhnroyal]

@agilob FYI if you have time to tackle some of the Dart issues

[agilob]

Might have more time in 2 weeks during Xmas break, but can't promise it.

[kuhnroyal]

Dart-dio now compiles with full OAS3 fake petstore.

[Grohden]

I'm curious, is dart generator working for you all using the current templates?
I had to fix a lot of cast issues from json conversions for the dart generator, here's my files if it help...
https://gist.github.com/Grohden/1fd8d110c806d8b239e88d07847c1e5a

But still I'm not able to even compile the project, there's still some issues with enum names :/

Edit: I've updated my gist, dart analyzer is kinda happy now, but I haven't tested it on runtime yet.
Edit 2: too soon, dart analyzer lied to me.

[wing328]

@Grohden are you using the latest master to generate the Dart API client? There's been many enhancements, bug fixes to the Dart generators

[Grohden]

@wing328 I'm manually copying the current master dart templates.
But I'm still on the latest released beta (must be on the beta3). Is there any way to use the master 'release' without cloning and building it myself? (a wget url)

[wing328]

You can find the snapshot version of the latest master in the project's README

[kuhnroyal]

@Grohden you can not only copy the templates, that is not enough, there are many changes in the generators as well.

The problems regarding json serialization are listed as todos.

[kuhnroyal]

@Grohden If you have specific solutions to the some of the json mapping problems, please don't hesitate to post them here. The dart generator is not my primary focus so any help is appreciated.

[kuhnroyal]

I have updated the known compile errors at the top.