Folks,
I was looking at few things today in Bugzilla, one of them is <https://bugzilla.mozilla.org/show_bug.cgi?id=519933
>. The gist of it is that Rhino CVS HEAD code now conforms to TC39
ES3.1 Draft of 9-Feb-2009, 8.12.4, step 2 and will throw a TypeError
when assigning to a property that has a getter but has no setter.
However, this was not really prohibited by earlier versions of either
ECMAScript or JavaScript. Rhino itself doesn't only support ECMAScript
5, it actually supports a whole range of JavaScript versions (and,
FWIW, ECMAScript 5 will only be used in JavaScript 2.0).
This brings about a question about the identity of the project. What
does Rhino strive to be? Do we want to be an ECMAScript runtime, or a
JavaScript runtime? What versions of ECMAScript and JavaScript do we
want to support with each release?
I believe that Rhino should be a JavaScript runtime, that is, not a
purely ECMAScript runtime, but also incorporating JavaScript features
as documented at <https://developer.mozilla.org/en/JavaScript>
As for version support... Rhino now has an awful lot of backwards
compatibility switches in it, and I'm a bit worried about maintaining
all of them.
Now, what version of JavaScript do we want to support? Right now,
Rhino has a bunch of VERSION_x_y constants that allow it to run in
older JS runtime compatibility mode. How far in the past do we want to
support that? Do we want Rhino to support a range of older JavaScript
versions, or do we declare that we will support whatever is the latest
JavaScript version, and tell people who need older JavaScript
functionality that they should go and use an older Rhino version?
I think we should be consistent about this. Current CVS HEAD seems to
have ECMAScript 5 functionality enabled by default (including the
above mentioned TypeError on setting a property with a getter but no
setter) that will ruin compatibility with previous JavaScript
versions. We either want every such functionality to be conditional
on, say, VERSION_2_0 (since JS 2.0 will be the ECMAScript 5 compliant
JS), or we should just throw away the compatibility idea and say that
going forward, we're only supporting a single JS version.
Attila.
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