Add support for rts-options

[sol]

This PR addresses #237 by adding explicit support for rts-options.

A note on semantics: When -with-rtsopts are specified multiple times then ghc only takes the last occurrence into account. For that reason, when a user wants to add additional rts options within a conditional s/he currently has to reiterate any outer rts options within the conditional, e.g.:

executable:
  ghc-options: '"--with-rtsopts -s"'
  when:
    condition: flag(with-threading)
    ghc-options: '"--with-rtsopts -s -N"'

I implemented rts-options so that they are combined in the same way as most other things we support. The following gives the same result as above:

executable:
  rts-options: -s
  when:
    condition: flag(with-threading)
    rts-options: -N

The tests show how this is mapped to .cabal: https://github.com/sol/hpack/pull/434/files#diff-c65aea3074dd2715b0aba52f9aaa1c5fa81b2ca89099c80150b41c33128a5262R1439-R1464

@snoyberg @quasicomputational @tfausak any thoughts?

[tfausak]

Nice!

The tests only show rts-options taking a string. Does it also allow for lists like ghc-options does (IIRC)?

[istathar]

I hope you will consider merging this. It would be a nice addition to hpack.

[tfausak]

Oh dear, I hope this hasn't been waiting for a review from me this whole time!

[tfausak]

Do these need to be quoted, like -with-rtsopts='-s -N'? Or perhaps the flag can be duplicated, like -with-rtsopts=-s -with-rtsopts=-N.

[sol]

From reading the motivation for this PR, this it's what I capture: Giving --with-rtsopts multiple times is not accumulative. That's the motivation for this PR in the first place.

Regarding quoting, I assume that what this PR currently does works with Cabal. I haven't tried it again just yet, but pretty sure that I tried when I originally wrote this.

--with-rtsopts='-s -N' may work as well, somebody would need to try. I'm fine with anything that works here, I'm not very opinionated on this.

[tfausak]

I just tried a bunch of things. Here are my findings:

• -with-rtsopts=-N and -with-rtsopts -N: Works as expected. Doesn't matter if you include the equals sign or not.
• -with-rtsopts=-N -K1k: Fails because it tries to pass -K1k to GHC rather than to the RTS.
• -with-rtsopts=-N -with-rtsopts=-K1k: Clobbers the -N flag. Same as setting -with-rtsopts=-K1k.
• -with-rtsopts='-N' and -with-rtsopts="-N": Fails because it doesn't interpret the quotes, which sends a literal '-N' to the RTS.
• '-with-rtsopts=-N -K1k' and "-with-rtsopts=-N -K1k": Works! It doesn't matter if you use single or double quotes.

TL;DR: I'd recommend "-with-rtsopts opt1 opt2 ...".

[tfausak]

This Cabal issue is very related: haskell/cabal#4818

[sol]

Thanks @tfausak for doing all the heavy lifting.

I rarely talk about it in public, but I have had issues with RSI for several years now. when it flares up, I have to stay away from the computer. This is the reason why sometimes I'm less responsive than what I would hope to be.

The TL;DR of it is that I am away from the computer. We still need the read me update, change log entry and version bump. I can try to take care of it eventually. But if somebody wants to lend a hand, then that's still very much appreciated.

Releases are fully automated once the version bump hits main.

[istathar]

I'd be happy to do the README.md update etc today.

[sol]

@istathar at the moment I don't have free cycles for this. If you want to help move this forward, this are the things we need:

• double check that it works as expected and optionally do some bikeshedding on the quoting
• update the read me
• add an entry to the change log

As a separate PR:

• bump the minor version

[istathar]

@sol happy to help with your checklist. I'll see if I can do that this week.