When exceptions occur in handler functions or helpers, call chunk.setError

[sethkinast]

If a provided handler or helper throws an exception, dust doesn't handle them gracefully. This makes it hard to quickly debug handlers.

This patch captures errors from helpers and handlers and uses chunk.setError() to ensure that dust passes the error along.

The easiest way to see the difference is to use the test page with the default asynchronous streaming example. Try adding

throw "Error!";

to either the stream or delay functions, or misspelling setTimeout in the delay function. In the current dust, you'll just see "Pending..." forever because dust has died and can't go on.

With this patch applied, you'll see the error captured and re-thrown dust-style, so that it's displayed in the error panel below the textbox.

[sethkinast]

Is there anything I could help out with to push this one along? It's fairly tiny but makes a big impact to not have uncaught exceptions getting thrown.

[rragan]

LGTM

[sethkinast]

Last bump before I give up for now.

[vybs]

we have been discussing how to do this in a generic and extensible way

see the PR #279

[rragan]

Which PR has the discussion?

[sethkinast]

Is there any chance of this making it in before I just fork the repo? Would like to save the effort if possible.

This is literally the difference between my entire Express server just crashing completely when something bad happens in a helper, and a graceful error output with the page continuing to render.

[jimmyhchan]

We are doing a lot of work now to add helpful debugging. This is definitely
a good use case. Communicating exceptions, debugging and errors in helpers
and in dust in general is currently missing.

Do you expect the template to try to keep rendering the stuff after the
helper?

[sethkinast]

Yes, I would expect a runtime exception to be handled the same way an errored chunk is-- the block emits an error, and the rest of the template parses as normal.

[jimmyhchan]

Currently the only thing that uses seterror is when a template is not
found. I believe the current implementation is to immediately stop
rendering. I could be wrong.

[michaelleeallen]

Just out of curiosity, why was this closed? Has this functionality been merged in a different PR? I need this same functionality for a UI library I am working on that runs in node.js, and when one of my helpers throws an error it shuts down the entire server.