Feature request: support for dartdevc and package:analyzer on web

[maks]

Following on from #50048 (comment) @Salakar mentioned:

But yes, Zapp.run does run the Analyzer and also dartdevc fully on web

It would be great to have support in the Dart SDK for dartdevc (could this be done by supporting compiling dartdevc to WASM in future as a target?) on web as that would allow projects like Zapp as well as DartPad to make use of this functionality rather than needing to maintain custom forks. This would also allow, as shown by Zapp, for DartPad not to have to use a white-list of allowed packages, as the compilation would be happening in-browser vs server-side as well as DartPad needing far fewer server-side resources.

Also same for package:analyzer from #50048 (comment)

Zapp is currently on the version of _fe_analyzer_shared that is shipped with the Dart version in Flutter 3.0.5 since I'm stuck with >upgrading to Flutter 3.3.0 and above - there's been a bunch of Analyzer/Compiler internals changes since 3.0.5 that have broken our >usage of compiler & analyzer on web completely

[nshahan]

@maks I'm not entirely sure what this issue is requesting for DDC. We don't expect DDC to be used outside of a build system because it is designed to compile modules separately and link the resulting JS files together at runtime. DDC doesn't do any of the modular breakdown itself and relies on whatever invokes it to decide what code should be compiled and what should be treated as dependency that will be compiled separately using the command line flags.

Perhaps understanding why are are using DDC could help.

• Does Zapp.run compile entire applications (user written source and dependencies) using DDC into one giant .js output?
• Do you pre-compile anything, like the Dart/Flutter SDK?
• Do you support debugging?
• Is there a reason you use DDC instead of dart2js?

In the case of DartPad, DDC is used because it can compile libraries modularly. That allows some white listed libraries to be precompiled which reduces the compile action down to just the code visible in the editor. All of the imported libraries are precompiled as separate JavaScript modules that are made available when running the users code.

[maks]

Sorry @nshahan I should have been more clear: I'm not affiliated with Zapp. I only referenced Zapp as I saw mentioned on the other issue comment that they needed to fork DDC to run in a web browser.

For myself, I have an intended use case that is similar: to be able to compile on the fly modules for use within a Flutter web app and I would like to do it all without any server-side support. Hence my need to be able to compile libraries in a modular fashion, as I intend to also code generate on the fly some of the Dart code I want to transpile to JS.

I also thought that having this support could then also be used by Dartpad to run completely in-browser as I find Dartpad very useful, but the current lag in the edit-compile-run cycle is not the best when it comes to the developer experience using it.

In regards to dart2js, I hand't considered it due to above, but in regards to your last bullet point about using it instead, does that mean that dart2js is supported for running within the browser?

[nshahan]

does that mean that dart2js is supported for running within the browser?

It is an interesting idea but currently neither of the web compilers (dart2js or ddc) support running in the browser.