Add Reviver

[Nexushunter]

Motive

I work on a project to provide a dart annotation that allows us to run the OpenAPI generator from a Dart defined config.

I was looking to provide a clean way to test our annotation and ensure that consumer could use a custom header delegate. In this case I wanted an easy way to be able to generically restore a header delegate that a user may provide but would like to have been able to avoid needing to know about their implementation details. ie User creates a subclass, they use the builder we provide and our builder needs to know nothing of their implementation details.

To help facilitate this it would be nice if the source_gen library had a way to revive the object in memory allowing for us to clean separate ownership (external library function vs internal library function).

While I know that the dart:mirrors library is classified as unstable it would be very beneficial to be able to have a solution provided to the community. This would also help with not having the need (though they could still be used) for packages like generic_reader.

Changes

• Add a Reviver class that uses dart:mirrors to reflect a ConstantReader / DartObject? into an in memory representation.

---

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[Nexushunter]

Trying to leverage these results in the following stack trace:

dart:collection                                       MapBase.map
package:source_gen/src/constants/reviver.dart 178:68  Reviver.toTypedMap
package:source_gen/src/constants/reviver.dart 93:16   Reviver.toInstance
package:source_gen/src/constants/reviver.dart 142:51  Reviver.namedValues.<fn>
dart:collection                                       MapBase.map
package:source_gen/src/constants/reviver.dart 139:74  Reviver.namedValues
package:source_gen/src/constants/reviver.dart 109:18  Reviver.toInstance
package:source_gen/src/constants/reviver.dart 135:50  Reviver.positionalValues.<fn>
dart:_internal                                        ListIterable.toList
package:source_gen/src/constants/reviver.dart 137:8   Reviver.positionalValues
package:source_gen/src/constants/reviver.dart 108:18  Reviver.toInstance
test/constants/reviver_test.dart 56:38                main.<fn>.<fn>.<fn>.<fn>

This feels wrong. The reason I'm doing this is because there is a limitation of not being able to do:

final t = Reviver.fromDartObject(reader.listValue.first)
              .toInstance()
              .runtimeType;

return reder.listValue.map((e) => Reviver.fromDartObject(e).toInstance() as t).toList();

[Nexushunter]

Opening this early to get some feedback and thoughts.