Hi V8 folks,

V8's error messages differ slightly from JSC's.  This is a problem because
it means that we Chromium WebKit folks are continually having to analyze and
re-update platform-specific "expected test output" files which include
output from the JS engine.

One example of this is WebKit/LayoutTests/html5lib/runner.html, which
changes daily (or even more rapidly) and thus has resulted in a lot of work
for us for a very long time.  We have to maintain several 5000-line-long
expectation files just for Chromium because of a single error message
difference: "SyntaxError: Parse error" vs. "Uncaught SyntaxError: Unexpected
token <".  And that's just one example.  I hope you can imagine why not only
doing this, but explaining the situation to each new WebKit sheriff, ends up
costing us in significant, ongoing ways.

Furthermore, it's wrong for these engines' outputs to differ in ways that
web authors can detect anyway.  When Safari and Chromium differ in other
ways, we seek to converge the two, because web authors need to be able to
treat the two identically.  Here it's the same: I don't have a vested
interest in which engine's messages "win", but the two need to converge.

I'm told this issue has come up before and there's been pushback that "we
like our error messages".  I'm sorry, but this isn't sufficient
justification for these kinds of differences.

It seems like it should be a fairly easy change to make the error outputs
match, and if there's significant value in V8's text over JSC's, to first
make the two match and then file bugs to improve both engines' messages
simultaneously.  If I'm missing something, please explain what; otherwise,
I'd like to hear a plan for how this can happen, or be told against whom I
should file an appropriate bug.

Thanks,
PK

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