[skybrian]

Tree shaking is helpful but not enough. It makes dependencies more fine-grained and binaries smaller by removing some false sharing. But library maintainers still have to be careful about true sharing, where a function calls another function, which in turn pulls in something big (like a lot of data stored in a constant).

You need both tree shaking and a community dedicated to keeping code small.

Javascript has the latter; it's not universally true, but lots of JavaScript libraries pride themselves on small code size and few dependencies.

That's great. But you can't stop doing that work just because you have a tree-shaking compiler. For example, there's a lot of work going into making Angular 2 apps reasonably sized and dart2js doesn't magically make it go away.

[mwcampbell]

You're right; tree-shaking doesn't eliminate all instances of dependency bloat. Come to think of it, I've even seen a counter-example in C++. On Windows, a hello-world application using the wxWidgets GUI toolkit is ~2.4 MB, even statically linked. I think the problem, or at least part of it, is that the WindowProc implementation uses a big switch statement to handle all of the Win32 window messages that wx supports. So, for example, the handler for the WM_PRINTCLIENT message has to be included even if your application doesn't do any printing. Same for drag and drop. It would be better if the WindowProc implementation looked up message handlers in a table, and the application could ask wx to register the handlers for just the features that are actually used. I wouldn't be surprised if similar concerns apply to frameworks like Angular, even in Dart.

[skybrian]

Yes, UI frameworks are especially prone to this. Anywhere you have generic "display arbitrary thing on the screen" functionality, it logically depends on all the code you might need to fulfill that promise for arbitrary input.

Custom HTML tags typically can have arbitrary children, so the issue inevitably comes up. The reason a normal web page can be small is because the browser has already been downloaded.