[whatwg] Discrepancies between HTML and ES rules for parsing an integer or float

Jonas Sicking jonas at sicking.cc
Thu Aug 4 22:57:44 PDT 2011

On Wed, Aug 3, 2011 at 11:21 AM, Aryeh Gregor <ayg at aryeh.name> wrote:
> Hixie just WONTFIXed two bugs that I thought might be of interest:
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=12220
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=12296
> Basically, HTML defines some algorithms for parsing integers, floats,
> etc., which are used in converting DOM to IDL attributes for
> reflection (among other things):
> http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#numbers
> The algorithms for parsing integers and floats are almost exactly the
> same as ECMAScript's parseInt() and parseFloat(), down to some of the
> language being copied word-for-word, but with subtle differences
> involving (at least) whitespace handling.  IMO, this is bad for
> several reasons:
> * It's confusing to both authors and implementers to have multiple
> almost identical algorithms.  Nobody's going to expect the discrepancy
> in the corner cases where it matters.
> * It's confusing to people reading the spec for there to be these
> extra algorithms defined, whose relationship to the ES algorithms is
> not obvious.  The HTML and ES algorithms are written in entirely
> different styles and it's hard to tell what the differences are from
> side-by-side inspections.
> * In at least some cases, all browsers match ES and none match the
> spec -- see <http://www.w3.org/Bugs/Public/show_bug.cgi?id=12296#c4>.
> * Browsers will have to maintain the ES algorithms as well as the HTML
> algorithms, so even if the HTML algorithms are superior, it doesn't
> save anyone the effort of understanding or implementing the ES
> algorithms.
> So I think HTML should just defer to ES here.  Hixie disagrees, and
> has resolved both bugs twice now, so I'm not going to reopen them
> myself at this point.  However, I'd like to hear from implementers
> whether they're willing to implement the spec as it stands, or whether
> they want the spec algorithms to be identical to ES's algorithms.

It would make sense to me to match ES here. The main concern is of
course website compat. Could someone detail what the differences would
be compared to what implementations/the HTML5 spec do now?

For parsing floats this would not seem like a problem though since
attributes containing floats is relatively new IIRC.

/ Jonas

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