Error stack

Geoffrey Sneddon gsneddon at
Sun Jun 10 06:56:57 PDT 2012

On 07/06/12 21:12, Jason Orendorff wrote:
> On Thu, Jun 7, 2012 at 1:37 PM, Erik Arvidsson<erik.arvidsson at>  wrote:
>> >  I wrote a new strawman for Error stack which is now available in some
>> >  form in all major browser (if betas are considered).
>> >
>> >
>> >
>> >  Feedback wanted.
> This isn't machine parseable in all cases, since the .message may
> contain newlines and can end with something like "\n  at ..."
> Changing this in Firefox would affect any Firefox addons that use
> Error.stack, but maybe we can take that hit.

It's not just Firefox addons that will break: GWT's output relies upon 
the exact format of Error.stack[1]. I know Google Wave depended upon 
this, and I believe other Google applications do too.

As such, I'm somewhat dubious as to whether we can actually change the 
format that much without breaking sites. For reference, we support 
Error.stack (supposedly identical to SpiderMonkey in format, though 
obviously not) and Error.stacktrace (which is meant to actually be human 
readable). Originally, we had Error.stacktrace as Error.stack, but it 
just broke too much (we spoof UA on some Google sites by default, and 
have to choose whether to go down IE/Fx/WK code-path, and often all 
three rely upon non-standard behaviour).


Geoffrey Sneddon — Opera Software

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