Editors & Tooling

Introduction

This place describes all the steps needed to get your code editors and other tooling working with IHP. When your favorite code editor is not described here, feel free to add your setup to this list.

You will also find steps on how to get autocompletion and smart IDE features. This is provided by haskell-language-server. IHP already comes with a bundled haskell-language-server, so you don’t need to install it manually.

Using IHP with Visual Studio Code / VSCode

Install the following extensions:

To make file paths clickable inside the web browser (e.g. when a type error happens), export this env var in your shell (e.g. in .bashrc):

export IHP_EDITOR="code --goto"

VSCode + Haskell Language Server Troubleshooting

“Couldn’t figure out what GHC version the project is using”

If you get an error Couldn't figure out what GHC version the project is using in Visual Studio Code make sure that the Nix Env Selector plugin was started correctly:

  1. Open the project in VS Code
  2. Click View -> Command Palette -> Nix-Env: Select Environment -> default.nix
  3. This will restart VS Code. After that Haskell Language Server should be working.

VSCode on Windows with Windows Subsystem for Linux

It is important to not access the files within the WSL from Windows itself (however, the other way around is ok). You can seamlessly (including auto-save) work on your projects within WSL from VS Code in Windows by adding the Remote WSL extension from Microsoft.

Using IHP with Sublime Text

Works great already out of the box.

Recommended packages:

To make file paths clickable inside the web browser (e.g. when a type error happens), export this env var in your shell (e.g. in .bashrc):

export IHP_EDITOR="sublime"

Using IHP with Emacs

Install the following packages from Melpa:

and put a .dir-locals.el file in your project root with:

((nil
  (dante-repl-command-line . ("ghci"))
  (haskell-process-type . ghci)))

Using IHP with Vim / NeoVim

Using CoC

Provided you already have CoC setup, just run :CocConfig and add the following segment.

{
    "languageserver": {
        "haskell": {
            "command": "haskell-language-server-wrapper",
            "args": ["--lsp"],
            "rootPatterns": [
                "*.cabal",
                "stack.yaml",
                "cabal.project",
                "package.yaml",
                "hie.yaml"
            ],
            "filetypes": ["haskell", "lhaskell"]
        }
    }
}

Haskell Language Server

Because haskell-language-server is tightly coupled to the GHC version it comes pre-bundled with IHP. In case you also have a local install of haskell-language-server you need to make sure that the one provided by IHP is used. Usually, this is done automatically when your editor is picking up the .envrc file.

When something goes wrong you can also run haskell-language-server inside the project directory (within a nix-shell). This might output some helpful error messages.

IHP Dev Server

Customizing the Web Browser used by IHP

When running ./start the application will automatically be opened in your default browser. You can manually specificy a browser by setting the env var IHP_BROWSER:

export IHP_BROWSER=firefox

You can disable the auto-start of the browser completely using echo as your browser:

export IHP_BROWSER=echo

Running the IHP Dev Server On a Host Different From localhost

If you run the IHP dev server on computer different from your local machine (e.g. a second computer in your network or a Cloud Dev Env like GitPod), you need to specify the right base url:

export IHP_BASEURL=http://some-other-host:8000 # App Url, Default: http://localhost:8000
export IHP_IDE_BASEURL=http://some-other-host:8001 # SchemaDesigner etc., Default: http://localhost:8001

Next time you use the dev server via ./start all links will use the right IHP_BASEURL instead of using localhost:8000;

Hoogle

To quickly look up function type signatures you can use the built-in hoogle server.

To install it:

  1. Open default.nix
  2. Add withHoogle = true; to the haskellEnv block, like this: 
let
    ihp = builtins.fetchGit {
        url = "https://github.com/digitallyinduced/ihp.git";
        ref = "refs/tags/v0.14.0";
    };
    haskellEnv = import "${ihp}/NixSupport/default.nix" {
        ihp = ihp;
        haskellDeps = p: with p; [
            cabal-install
            base
            wai
            text
            hlint
            p.ihp
        ];
        otherDeps = p: with p; [
            # Native dependencies, e.g. imagemagick
        ];
        projectPath = ./.;

        withHoogle = true; # <-------
    };
in
    haskellEnv

Run nix-shell --run 'make -B .envrc' to remake your dev env.

After that you can use the following command to start hoogle at localhost:8080:

hoogle server --local -p 8080