Streamly Dev Shell

Nix shell based development environment for Haskell Streamly ecosystem. Includes the following:

• Haskell compiler - ghc
• Haskell project build tool - cabal
• Streamly ecosystem libraries
• Hoogle server for documentation
• Haskell language server (HLS)
• A few other Haskell dev tools
• Vi editor nvim
• Visual Studio Code editor codium

Check the nixpkgs version in default.nix.

Please refer to this page for Haskell language server features.

How to use the Shell?

To get a shell with the development environment installed in it, use the following command:

$ nix-shell https://github.com/composewell/streamly-packages/archive/v0.1.0.tar.gz

By default everything is installed. If it takes too long or uses too much disk space, you can pass arguments to the nix expression to customize install, for example:

$ nix-shell --arg haskell-tools false --arg hoogle false ...

Check out default.nix for all available options.

Once you are in the shell, you can use ghc, cabal, nvim, codium, hoogle, and other tools from the PATH. ghc will have streamly packages installed in its package database, so you can directly use it without any package downloads.

Cloning the streamly-packages repo

To run the nix-shell, you can also clone the streamly-packages repo and run nix-shell from the repo root directory.

$ git clone https://github.com/composewell/streamly-packages

This is especially useful if you would like to customize the environment before using.

Updating package versions

To update the versions of Haskell packages included, edit the nix/haskellPackages.nix file to specify particular git commit ids or package versions from hackage to be used.

Changing a package version may break other packages dependent on the changed package. If you do not need the broken packages you can comment those in default.nix. Otherwise change the versions of the broken packages as well accordingly.

Accessing the documentation

Inside the nix shell, run the following command:

$ hoogle server --local -p 8080

Open the URL http://127.0.0.1:8080 in your browser.

Using vim editor

Inside the nix shell, run the following command:

$ nvim

Use ESC :q to quit. Use ,h for help. Use :colorscheme morning if you want a light theme.

Add the following to your $HOME/.config/nvim/coc-settings.json to use the haskell language server with nvim:

{
  "languageserver": {
    "haskell": {
      "command": "haskell-language-server-wrapper",
      "args": ["--lsp"],
      "rootPatterns": ["*.cabal", "stack.yaml", "cabal.project", "package.yaml", "hie.yaml"],
      "filetypes": ["haskell", "lhaskell"],
      "settings": {
        "haskell": {
          "checkParents": "CheckOnSave",
          "checkProject": true,
          "formattingProvider": "fourmolu"
        }
      }
    }
  }
}

Using VSCode editor

To run VSCodium, the open source version of Microsoft VSCode, run the following command in the nix-shell:

$ codium

If you have started the nix-shell with haskell-tools included, you will have the Haskell Language Server installed in the shell. If you get a pop up saying: "How do you want the extension to manage/discover HLS and the relevant toolchain?" just choose, "Manually via PATH".

You can also set it later in the following section in settings:

• Extensions
  • Haskell
    • Manage HLS
      • PATH

If you wish to use your existing installation of VSCode instead of codium from the nix-shell, you can do that too, just make sure to run it from within the nix-shell so that it is able to use the installed Haskell tools and libraries. For example, on MacOS, if you have your vscode app in Downloads folder:

$ open ~/Downloads/Visual\ Studio\ Code.app