Can not skip dart:mirrors

[valotas]

Environment:

• Dart VM version: 2.0.0 (Fri Aug 3 10:53:23 2018 +0200) on "linux_x64"
• build_runner: 0.10.1+1, build_test: 0.10.3+1
• build_web_compilers: ^0.4.0
• linux
• code: https://github.com/valotas/mustache4dart/tree/dart2browser

I get the following:

[SEVERE] build_web_compilers|ddc on lib/src/reflect.module (cached):
Error compiling dartdevc module:mustache4dart|lib/src/reflect.ddc.js

[error] Cannot import "dart:mirrors" in web applications (https://goo.gl/R1anEs). (package:mustache4dart/src/reflect_with_mirrors.dart, line 1, col 8)

Please fix all errors before compiling (warnings are okay).
}

which is true but reflect_with_mirrors.dart is conditionally imported only when dart.library.mirrors is available.

Is this behavior intended?

[matanlurey]

I don't believe that conditional variable is actually supported.

[valotas]

Supported by dart or by build_web_compilers? How can I conditionally use mirrors?

[matanlurey]

I do not believe you can

[matanlurey]

We should probably fail early on unsupported conditional literals?

@jakemac53 @natebosch

[natebosch]

We're moving forward with conditional import support. Not sure of a timing yet

[valotas]

Is there any workaround for the moment? The only thing that I can think of is completely different entry point for the browser.

…

On Sat, Aug 25, 2018, 23:13 Nate Bosch ***@***.***> wrote: We're moving forward with conditional import support. Not sure of a timing yet — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1790 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABn8xYNU8ArOD-HWoq1sNRiQUT1Q2ESks5uUb3hgaJpZM4WMfmW> .

[jakemac53]

Yes the only thing that works today is a totally different entrypoint, using dependency injection or something to provide the correct implementation for the platform.

I am working on support for this feature currently but its a little ways out still from landing.

[jakemac53]

Ok, @valotas if you update to the latest build_modules/build_web_compilers/build_vm_compilers (likely just requires a pub upgrade), then this should now be supported.

Please file any issues if you have trouble!

[jakemac53]

Do note though that at least for now you will have to add // ignore: uri_does_not_exist comments on your config specific imports, at least until dart-lang/sdk#34177 is resolved.

[jakemac53]

Actually @natebosch made a good point that you are also using config specific exports, there is also an SDK issue for those (they don't work at all unfortunately, due to an analyzer issue). You can follow along at dart-lang/sdk#34179, as soon as it is fixed in the sdk there shouldn't be anything required on the build package side of things.

[valotas]

It looks like it works! Thanks for the quick response!