> On Aug 29, 2016, at 1:16 AM, Carlos Garcia Campos <carlo...@webkit.org> wrote:
>
> Does that mean than from the WebIDL point of view all methods can now
> raise a exception? If don't tell the code generator that a method can
> raise a exception, we assume all could return a Exception?
Correct.
Once the transition is done, the IDL will no longer indicate which functions
can raise exceptions; the return types of C++ member functions will, instead.
During the transition, exceptions can be indicated in either way.
> It actually depends on whether this is an exception or not.
I’m not sure exactly what you mean. But I expect us to keep driving JavaScript
DOM bindings forward in lots of ways. Here are a few:
- We will add support for more WebIDL features. There are many still to go. In
some cases that means removing code that is currently in the DOM that is doing
part of the bindings work and using WebIDL to implement this things. For
example, translation of strings into enum values. WebIDL includes a
specification of how all these features are reflected in JavaScript, but for
non-JavaScript bindings we have to define how to reflect each feature.
- We will add better exception messages, which means DOM code has to provide
more than an exception code.
- We will update bindings with changes to move the web platform forward, with
JavaScript-specific strategies for backward compatibility that won’t
necessarily work for other languages such as Objective-C. For example, the
latest specifications turn DOMImplementation.hasFeature into a function that
ignores its arguments and always returns true. That’s easy to implement with
WebIDL for JavaScript, but for GObject and Objective-C we need code somewhere
that remembers what the old argument list was.
- We will update bindings with changes that have minimal observable effect in
the JavaScript type system but have effects on types of arguments or return
values in GObject bindings, such as making a return type more specific (Attr
instead of Node) or changing which numeric type is used.
- We will move things currently done in the DOM itself into the bindings.
- We would like to change the bindings generation scripts to run more quickly
and so that fewer run when a given IDL source file is changed.
> If you really think that build is going to be broken often because of things
> very difficult to do in the GObject bindings, then we should indeed find a
> more general solution. Otherwise I prefer to solve this problem now, and keep
> the existing way of generating the bindings. We can add a rule that you can
> break the GObject DOM bindings build, to not block your work, and I'll try to
> fix it asap as we currently do with WebKit2.
Something like this might work. But coping with these changes is going to be
challenging.
I expect we are going to continue to run into many things we want to do for
JavaScript that are difficult to do in the GObject bindings. It’s taken many
people hundreds of hours already to add these various WebIDL features for the
JavaScript bindings, and each one involved changing both the bindings and the
underlying DOM implementation.
I think the 88 already existing #if statements in the IDL are one indication
that the IDL-based code generation strategy isn’t working very well; *many*
features that are simply not supported outside the JavaScript code generator
because they use one of the newer IDL features are another.
If you read the latest WebIDL draft <https://heycam.github.io/webidl/> you will
see lots of features that are tricky to deal with—dictionary types, enumeration
types, callback function types, promise types, union types, regular
expressions, frozen arrays, stringifiers, serializers, indexed properties,
named properties, overloading, map like, setlike—the only reason this is not a
crisis is that many web APIs are old and so not built on any of these new
concepts. Over time, critical features are being built on them.
I am OK with the “it is OK to break the GObject bindings build” strategy, I
guess, but are you sure you are OK with that?
— Darin
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