ceylon/ceylon-js

Collect stack trace with Error.stack

Closed this issue · 6 comments

lucaswerkmeister commented

Throwable uses .caller to collect the stack trace. However, use of .caller is explicitly prohibited in ES5 strict mode; thus, attempting to create a Throwable in strict mode fails with a TypeError. (This was the cause of eclipse-archived/ceylon-web-ide-backend#75.)

All modern engines also offer another way to get a stack trace: Error().stack. This is, unfortunately, also unspecified, but available even in strict mode. Therefore, I think Throwable should try to use that first, and only fall back to .caller if Error().stack isn’t available.

quintesse commented

I think this is actually an issue for the language module. But anyway I've added some try-catches around the .caller bits so strict mode will at least not cause any problems anymore.

lucaswerkmeister commented

Well, if an empty stacktrace isn’t a problem, sure :P

(And yeah, this probably belongs in ceylon.language, didn’t think about that. Sorry.)

chochos commented

I've wondered about this before. But this stack won't have any refs to Ceylon code, just the generated code (not like we show source locations anyway). I guess we could make Throwable extend Error, or maybe just use Error.stack inside its constructor... or maybe the throwexc function from the language module could use that.

lucaswerkmeister commented

or maybe just use Error.stack inside its constructor

yes, that’s what I meant – check Error().stack (stack of new error) in the Throwable constructor, where we currently walk .caller.