[webkit-dev] Swift in WebKit

Ryosuke Niwa rniwa at webkit.org
Mon Jul 28 17:10:28 PDT 2014

On Mon, Jul 28, 2014 at 12:47 PM, David Farler <dfarler at apple.com> wrote:

> Hello all,
> I have the following bug to help build out support for layout tests in the
> iOS Simulator.
> iOS Simulator LayoutTestRelay
> https://bugs.webkit.org/show_bug.cgi?id=135269
> I'd like to include this as a new tool written in Swift.
> Why I think it's fine in this case:
> - This tool is specific to the iOS and OS X platforms
> - Swift is a fully supported, albeit new, language starting in Xcode 6.
> - Swift is probably the best way to get Objective-C bridging "for free" in
> the long term
> - Swift supports script-like "immediate mode" with good JIT-compiled
> performance
> - The tool's size and scope is sufficiently small with no complex or
> WebKit-specific dependencies

There is a precedence of WebKit rejecting the use of new programming
languages in the past:

In particular see Maciej's response in

I understand that its freshness and continual evolution means that we won't
> reviewer support relative to our C family languages. I would argue that it
> will be difficult to subjectively tell when the time is "right", that a
> good way to solve that is to start using the language itself, and take an
> incremental approach to crafting the Swift story in WebKit. Using it for
> some simple tools is a good place to start.

Could you clarify what the advantage of using Swift is?  Personally, I'm
not interested in learning a yet another platform-specific language to hack
on WebKit.

I'm not saying that Swift is a bad language or anything but I don't want to
start having people writing random programming languages such as Haskell,
Scala, Go, Rust, etc... deemed hip/cool at the time to create new tools in

It would increase the entry barrier of working on those tools even if they
were specific to one platform.

e.g. what should GTK+/EFL contributors do if they wanted to modify the way
webkitpy works and needed to make changes to your tool?  Or do you think
such a scenario is extremely unlikely?

The larger discussion of using Swift in larger AOT-compiled contexts but is
> probably going to happen in this thread anyway, so let's have it:
> *What of future use of Swift in WebKit?*

I would really like to know why we should use Swift in WebKit at all in the
current stage?

- R. Niwa
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