[dart][dart-dio] Next-gen dart-dio generator (!8869) · Merge requests · OpenAPI Tools / openapi-generator

This is work in progress but examples compile and tests run locally. This needs an updated Dart version in CI.

This PR establishes a next-gen dart-dio generator with breaking changes around null-safety which can not be implemented in backwards-compatible ways.

Features & changes

Dart 2.12.0+ requirement
Dio 4.0.0+ requirement
null-safety implemented
new package layout with a single exported file
wrapping of serialization errors in DioError
named parameters for all API params
support for different serialization libraries with built_value being the current only and default implementation
enforce dart format in CI (waiting on https://github.com/dart-lang/sdk/issues/44582)

need a solution for serializing null with built_value (https://github.com/google/built_value.dart/issues/912)
need to handle unused_import analyzer warning in polymorph model classes
wait for timemachine to support NNBD (https://github.com/Dana-Ferguson/time_machine/issues/55)

Read the contribution guidelines.
Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
Run the following to build the project and update samples:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
File the PR against the correct branch: master, 5.1.x, 6.0.x
If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.