Using a browser API that returns Promise

[jonasfj]

I've trying to use window.crypto.subtle.generateKey and got crypto_subtle.dart working on dartdevc and dart2js, but flutter run -d web-server --release is broken (I couldn't reproduce the issue with dart2js -O4).

If I use CryptoKey from dart:html, I can get it working on flutter run -d web-server --release, as well as flutter test --platform chrome, but not dart test -p chrome.

Minimal example with comments:
https://gist.github.com/jonasfj/30d7a41b57d1af9b84edb039f1912011

Context: google/webcrypto.dart#7

[sigmundch]

Thanks for the bug report!

Indeed, there is an internal limitation that disallows us to use JS-interop on types that are already expose in dart:html (what we call "native" types). This is a tricky and brittle part of JS-interop today that we hope to improve it this year.

Short term, @srujzs is about to land a change that will check and report a compile-time error if we detect this issue. We can't always detect it, but in the example you showed above we would have.

[johnniwinther]

I think I observed something similar trying to use Window.requestFileSystem. This is defined to return a Future<FileSystem> but however I tried to access it, I always ended of with a failure because the async system expected the value to be have a correct Dart type but instead was a native JavaScript object.

[sigmundch]

@johnniwinther - I believe your issue with requestFIleSystem is due to #45036

[srujzs]

Right, the symptoms seem identical to that issue.

Addressing the original issue though, you can still workaround this limitation (that won't break in unexpected ways) by using @anonymous classes for CryptoKey.