1435276 - Use new prefs parser in mozprofile Rust port

Status: NEW

(Testing :: Mozbase Rust, enhancement, P5)

Description

[Andreas Tolfsen ❲:ato❳]

geckodriver uses a minimal Rust port of mozprofile to parse, read,
and write prefs to profiles prior to starting Firefox.  As of bug
1423840 Firefox transition to a preference parser written in Rust.
It lives in-tree under modules/libpref/parser and we should be able
to make mozprofile pick that up by path.

Because libpref is not as far as I know a published crate, moving
to it would mean that we couldn’t release geckodriver from GitHub
anymore.  This seems like a minor inconvenience since we want
to move releases onto TaskCluster.  So either we need to solve
releasing from TC first or we need to live with the prospect of
manually uploading binaries to GitHub for some transition period.

Comment 1

[Arthur K. (he/him)]

Can the perf changes in Rust 1.25 be leveraged here (or elsewhere)?

https://blog.rust-lang.org/2018/03/29/Rust-1.25.html

Comment 2

[Andreas Tolfsen ❲:ato❳]

(In reply to Arthur K. from comment #1)
> Can the perf changes in Rust 1.25 be leveraged here (or elsewhere)?
> 
> https://blog.rust-lang.org/2018/03/29/Rust-1.25.html

What specifically are you referring to?

Comment 3

[Arthur K. (he/him)]

LLVM6(In reply to Andreas Tolfsen ‹:ato› from comment #2)
> (In reply to Arthur K. from comment #1)
> > Can the perf changes in Rust 1.25 be leveraged here (or elsewhere)?
> > 
> > https://blog.rust-lang.org/2018/03/29/Rust-1.25.html
> 
> What specifically are you referring to?

LLVM 6.

Comment 4

[Andreas Tolfsen ❲:ato❳]

I’m not sure what effect LLVM 6 will have on porting mozprofile to
use the new Firefox prefs parser, but generally speaking central
is compiled with Rust stable, so whatever performance improvements
we get from upgrading our compiler we will also get for mozprofile
(and geckodriver).