Stability of mirror system for Dart VM

[roman-vanesyan]

Stability consideration for mirror system since Dart 1 mirror system is considered as unstable. There was been another major bump of Dart as Dart 2 was released, were in mirror system is also considered as unstable, before stable release it's been a bit unclear will mirroring be introduced also in Dart 2 or not, now we have it. But can you, please, clarify the state of the mirror system for Dart 2 and what future for it is planning? Mainly I speak here about Dart VM.

[a-siva]

You mention that the mirror system was considered unstable in Dart 1, can you elaborate on that with specifics of what is unstable.

In Dart 2 we intended to maintain the same support that we had for dart:mirrors, there could be some issues that we overlooked. Could you elaborate on what you have found.

[zoechi]

Mirrors support was marked experimental for dart2js as far as I remember and
removed entirely in Dart 2 dart2js and Flutter.
Only the server VM supports mirrors in Dart 2.

[eernstg]

It might be relevant to know the following: In a setting where 'dart:mirrors' is not supported you can do most of what 'dart:mirrors' will do using code generation with package reflectable.

[roman-vanesyan]

@a-siva it is right in the documention of 'dart:mirrors' package, here is fragment from that comment:

 * ## Status: Unstable
 *
 * The dart:mirrors library is unstable and its API might change slightly as a
 * result of user feedback. This library is platform dependent and therefore it
 * has implementations for both dart2js and the Dart VM. Both are under
 * development and may not support all operations yet.

@zoechi Yes, I'm primary about VM support for it.

@eernstg I considered reflectable previously, but the way codegen works is IMHO awful, because of the way it generates code, for example that part of that makes IDEs mad, until code is generated, plus classes with ugly names that we should extend in implementation classes.

[eernstg]

@vanesyan,

for example that part of that makes IDEs mad, until code is generated,

In fact, reflectable does not generate any part files, it generates a single file which is intended to be imported from the library that contains your main.

plus classes with ugly names that we should extend in implementation classes.

That is also a property that reflectable doesn't share. However, it may of course be true that your setup will create some situations where the generated file does not yet exist and an IDE may be confused about that (there are many ways to set up your working environment, so I don't know exactly how code generation is triggered and how that's integrated with your IDE).

[a-siva]

At this point we have no plans for enhancing dart:mirrors library.
Please see #44489 which is investigating a path towards discontinuing support for dart:mirrors