Getting a formula written to build haskell-language-server

[ELLIOTTCABLE]

I'm attempting to write a formula for haskell-language-server; I haven't written a formula in many years, so please forgive me if I say anything dumb!

HLS requires several downloads, per version: https://github.com/haskell/haskell-language-server/releases/tag/0.7.1

• the haskell-language-server-wrapper binary,
• and an haskell-language-server-8.8.2 (or similar) binary for each version of GHC being used in conjunction.

Realistically, I think the best solution is to download all of them — there's only a half-dozen or so, and I don't think having a few haskell-language-server-macOS-N.N.N copies in /usr/local/bin is a huge deal.

That said, is there a best way to go about this in a formula? Any directions or advice? I don't want to do a huge hack if I don't have to!

[carlocab]

I think the answer here is that you're not meant to download any of them: https://docs.brew.sh/Acceptable-Formulae#we-dont-like-binary-formulae

The only exception is when the binary you're downloading is for the purposes of bootstrapping at build-time. These binaries are thrown away when the build is complete. (Still, we try to avoid these where we can.) If that's the case here, I don't know if there's a better way than using multiple resource blocks.

[kret]

How about a cask roughly like this: kret/homebrew-cask@e14dd52?
...just download and decompress a full macOS release, with wrapper and all versions?

I did not specify there the dependencies as it seems to me that there are several, different, preferred setups of GHC/stack/cabal/etc that specifying dependencies might actually break some devs' environment. Could be updated, of course.
At the moment ghc formula is at version 8.10.3 and hls 0.7.1 does not provide a version for it (https://github.com/haskell/haskell-language-server/releases/tag/0.7.1). hls 0.8.0 should provide this support, and be released soon, though.

This cask seems to work with nvim, command line execution.
However, in order to persuade VSCode to use this hls I had to install the cask with brew install haskell-language-server --no-quarantine or suffer the manual macOS security overrides in System Preferences > Security & Privacy.
I did not find a ready solution for putting the --no-quarantine into the cask itself.
I could use caveats to inform users of --no-quarantine? Seems to be a bit too late, though.
Not sure how to best approach this.

Please let me know what you think, or just feel free to use/expand this solution :)

[kret]

Updated cask on my branch to hls 0.8.0 kret/homebrew-cask@7d7acb3. Now it covers GHC 8.10.3 so same version as ghc Homebrew formula.
Should be easier now to add depends_on, if you preferred that.

[kret]

...more humane link to proposed cask file: https://github.com/kret/homebrew-cask/blob/haskell-language-server-cask/Casks/haskell-language-server.rb

[carlocab]

Note that this may not be an acceptable Cask: https://github.com/homebrew/homebrew-cask/blob/master/doc/faq/rejected_casks.md

The app is both open-source and CLI-only (i.e. it only uses the binary artifact). In that case, and in the spirit of deduplication, submit it first to Homebrew/core as a formula that builds from source. If it is rejected, you may then try again as a cask (link us to the issue so we can see the discussion and reasoning for rejection).

[kret]

So far I have succeeded with...

• a cask for a full hls 0.8.0 release: https://github.com/kret/homebrew-hls/blob/main/Casks/haskell-language-server-all.rb,
• a formula for hls 0.8.0 with GHC provided by homebrew (8.10.3) https://github.com/kret/homebrew-hls/blob/main/Formula/haskell-language-server.rb.

Cask

• 👍 all-in-one package, as built by hls maintainers,
• 👎 needs to be installed with --no-quarantine switch or user needs to manually
  confirm security exception for each binary in System Preferences
  as they are being executed first time :(

Is there a way to make this cask not---no-quarantineable?

Formula

• 👍 follows Homebrew guidelines,
• 👎 uses a build command ripped out of https://github.com/haskell/haskell-language-server/blob/3464ed8b6ba1fbc443dae95f9edb2e07420b1b26/install/src/Cabal.hs#L61
  which is very fragile and would need to be updated every time hls maintainers update their build setup,
• 👎 is probably not useful to Haskellers that work on any project with GHC version different from Homebrew-provided one

Feel free to comment.

[ELLIOTTCABLE]

Okay, I've done a little more investigation into this. I'm a newbie, so I don't know if I'll be able to complete this process myself, but maybe somebody coming through later can benefit from my investigation.

The problem here is mostly that:

1. haskell-language-server needs to be built for the specific GHC version it's going to be used with.
2. End-users may have any GHC revision installed, and expect haskell-language-server to work with that revision.

Upstream, this is solved by shipping haskell-language-server-wrapper, along with a bunch of pre-built haskell-language-server-N.N.N binaries that work with a specific GHC version. (As described in my misguided OP, heh.)

Further complicating this, is "what GHC versions is a given Joe Enduser on Homebrew using" is actually non-trivial:

1. They may have brew install ghc'd, and thus have a bare, specific version of GHC installed; but not have Cabal or Stack installed
2. They may have brew install stack'd, and their Stack install may have one-or-more versions of GHC installed thru Stack,
3. Or they may have installed stack or ghcup or other tooling, and not used Homebrew at all to install Haskell, while still expecting brew install haskell-language-server to work without intervention.

Upstream, the project handles this with a custom build-system that queries Stack and cabal, attempting to determine what versions of GHC it should build against. /=

So, tl;dr I'm not sure how to solve this in a single Formula, that we can put in homebrew-core, that supports all three of the above categories. I'm guessing we'd have to have CI build all of the possible GHC versions, so that the single haskell-language-server bottle contains whichever specific binar(y|ies) a given user may need ... but I don't know the blessed way to write such a formula. (In particular, the naive way I can think of doing that, would result in a user who doesn't use bottles, building a dozen versions of GHC, from source, in serial, to build a dozen versions of haskell-language-server, that they don't need ... yikes. Especially-yikes given how famously slow GHC is to build.)

I hope somebody smarter than me, or more familiar with Haskell than me, or more familiar with Homebrew than me, can figure this out!

---

Here's my initial naive attempt, although I haven't had much luck getting it to work:

class HaskellLanguageServer < Formula
  desc "Integration point for ghcide and haskell-ide-engine. One IDE to rule them all."
  homepage "https://github.com/haskell/haskell-language-server"
  license "Apache-2.0"

  # Use the tag instead of the tarball to get submodules
  url "https://github.com/haskell/haskell-language-server.git",
      tag:      "0.7.1",
      revision: "e4f677e1780fe85a02b99a09404a0a3c3ab5ce7c"

  head "https://github.com/haskell/haskell-language-server.git"

  livecheck do
    url :stable
    strategy :github_latest
  end

  depends_on "cabal-install" => :build
  depends_on "ghc" => :build
  depends_on "icu4c"

  def install
    system "cabal", "v2-update"
    system "cabal", "v2-run", *std_cabal_v2_args,
      "./install.hs", "--project-file", "install/shake.project"
  end
end

[gromgit]

I'm not sure how to solve this in a single Formula, that we can put in homebrew-core, that supports all three of the above categories.

I wouldn't worry about that. Since you say HLS is tightly coupled with GHC, focus on getting your formula working with the current ghc formula (I assume that the latest release in both projects at any time are guaranteed to be compatible). Trying to do what you describe is like leaping from "weekend jogger" to "Iron Man pack-leader" in a day -- you'll just drown.

[carlocab]

Ok, let's just try to simplify this problem a bit. Guaranteeing compatibility with software that wasn't installed using Homebrew is difficult and untestable (in particular, not tested by Homebrew CI), so let's consider that nice-to-have-but-not-necessary.

They may have brew install ghc'd, and thus have a bare, specific version of GHC installed; but not have Cabal or Stack installed

We can add hard dependencies to cabal and stack if they're necessary. I think the goal here at minimum, would be to get the language server to work if the user has Homebrew ghc installed. If it'll work with Homebrew [email protected] and [email protected] too, even better.

[jneira]

haskell-language-server is on hackage now and can be installed in a more friendly way with cabal install: https://hackage.haskell.org/package/haskell-language-server

[kret]

Solution suggestion: Homebrew/homebrew-cask#100527.
This downloads a full official HLS macOS release and makes available on path.

Inconveniences

• macOS security warnings will popup once each binary is run. This can be worked around using Homebrew's --no-quarantine flag while re/-installing the cask.
• There are no dependencies on Homebrew's GHC/Cabal/Stack specified because it is my understanding that there are several way for projects to fetch those.

Alternative solution might be to create a cask for each binary (available as part official releases too: https://github.com/haskell/haskell-language-server/releases/tag/1.0.0) so that users can pick specific ones...

[jneira]

mmm not sure how much time cost download all of them but it is the simplest solution so i would go for it, you can always create independent cask for specific versions afterwards (maybe not all of them but the more popular ones?)

[kret]

Well, PR was rejected, as suggested earlier on this discussion 😄 (Homebrew/homebrew-cask#100527 (comment)).
As to the time to download and unpack the full HLS cask, it was about 20s on my laptop (not the fastest internet connection). I would not mind, 20s and I could use HLS in any project supported by it 🚀 🪐