Need a way to trap exceptions that reach top-level

[dgrove]

In the browser, it's important to have a way to catch top-level exceptions so that they can be logged to servers.

Not sure if this will wind up being an embedder issue or a language issue.

[gbracha]

The spec already notes:

    If an uncaught exception is thrown by a running isolate A, A is immediately suspended.

Not terminated, suspended. The non-normative text describes the relation to the embedder, which should get a description of the exception (this is described for compilation errors). It's possible we should make some this text normative and clarify that it applies to uncaught exceptions.

Ultimately, this is the easy part. The key thing is the SMOP, and it seems clear to me that the embedder should deal with this situation. Unless you want resumable exceptions, I don't see why the language runtime would need to do very much.

[jmesserly]

I don't think "suspended" is the desired behavior for the main browser isolate. The Dartium embedder can't do anything here, because it doesn't know how to talk to web server. This must be handled by application's code. We would like the application to register a handler that can respond to the exception and deal with it.

The case we are concerned with is an exception in the main isolate, such as in an event handler, requestAnimationFrame, setTimeout, etc. It is not always possible to ensure a try-catch on every event handler.

[nex3]

I think this is a duplicate of issue #8417.

[jmesserly]

good call Nathan. Dup'd with your bug

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Added Duplicate label.
Marked as being merged into #8147.

[sigmundch]

(fixed dup reference)

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Marked as being merged into #8417.