Gauge interest in and fixes/features wanted for TLS for 2.10.x

[milessabin]

2.12.0 has arrived, but lots of people are still stuck on 2.10.x. In principle it would be possible to backport fixes and features from 2.11.x and 2.12.x to Scala 2.10.x to make it easier to support cross building across all three major versions without unduly limiting people's ability to exploit new features of 2.12.0.

Things we might consider adding are,

• Fix for SI-2712
• Fix for SI-7046
• Literal types
• Right biased Either

Please indicate your general interest here and add additional fixes/features in comments. Nb. things which aren't already supported on both 2.11.x and 2.12.x are unlikely to be considered.

Could people reacting with a 👍 or 👎 please give their reasons pro/con.

Nb. This isn't a question about whether we think other organizations ought to move to 2.11+ (whatever we might think, some don't have an easy choice) ... it's a question about whether we allow ourselves to use newer language features in our own projects while we continue to support users who can't move forward (if that's what we choose to do).

[adelbertc]

Whatever is causing FS2 to not compile on 2.10.x would be awesome. It seems like something in Scala 2.10 is demanding some silly hand-holding, see: typelevel/fs2#755

A lot of the error messages are something like "expected Handle[F, A] found Handle[F[_], A]" Some silly type annotations (shown in the ticket linked above) seem to make the compiler happy.

This may also simplify life for libraries using FS2 like Doobie and HTTP4S. /cc @tpolecat @rossabaker

[milessabin]

@adelbertc are you able to identify the commit that fixed this in 2.11.x? Try a git bisect.

[nafg]

Is right-biased Either source-compatible?

[milessabin]

@nafg it's neither source nor binary compatible. I don't think that's a problem ... the point of this would be to build a bridge between a now unsupported old release and current releases.

[milessabin]

FWIW, a backport of right biased Either to 2.11.x would be highly desirable.

[nafg]

@milessabin I don't get it. Supposing I have a project that I can't upgrade because it uses library X which only exists for 2.10, if library X uses Either and I upgrade to 2.10.N with changed Either, won't I get runtime linking errors inside of X?
(Same for 2.11)

[milessabin]

@nafg the 2.12.x change is binary incompatible, but I'm fairly confident we can come up with something which is binary compatible with 2.10.x and source compatible with 2.12.x.

[milessabin]

Would people reacting with a 👍 or 👎 please give their reasons pro/con.

[rossabaker]

When I was stuck on Scala 2.10, I would have welcomed this. TLS Scala has been an easy and positive transition wherever I've tried. But my organization had cooled to Scala and had zero interest in a using a compiler fork. We were on 2.10 because we were slowly divesting ourselves of Scala. If this is why others are on 2.10, this may excite individual developers but see little adoption.

If people are on 2.10 and committed to Scala in some form, then 👍.

[tpolecat]

This would let me simplify some things in doobie and potentially support some new stuff in 2.10 that I wasn't planning on. But I'm concerned that the long-term effect will be an increased maintenance burden on all of us, since we're removing the main motivation to upgrade. So I don't have strong feelings one way or the other. I do suspect that the main beneficiaries are likely to be large orgs, who might be in a position to pay Lightbend to do this if it's that important.

[fommil]

ensime is only supporting 2.10 until sbt 1.0 comes out, which will probably coincide with ensime 3.0 (sometime in 2017). We're not currently using any TLS features.

[non]

This is something I said in the Gitter channel:

so my 2¢ for scala versions is that i think it makes sense to support at least 2.5 scala major versions. by which i am agreeing a bit with @alexandru -- dropping 2.10 support at 2.12.0 doesn't seem like a good plan, but dropping it by say 2.12.3 (or so) doesn't seem bad to me.

I'm not totally convinced that I think supporting 2.10 in perpetuity is important, but I will continue supporting it for awhile longer at least.

[milessabin]

@dwijnand @julien-truffaut @mpilquist ... could you elaborate on your 👎's? Is that an active dislike? Or just lack of interest? Or something else?

[dwijnand]

Because of the maintenance costs - I'd personally prefer Typelevel focus on pushing the language forward of the burning edge side, rather than spending (the precious, little, volunteered) effort on the legacy side.