6. Editor setup

Reference: {#DevEditor}

This page provides tips for setting up editors to work with the Wire codebase.

6.1. For multiple editors {#DevAll}

6.1.1. Using Haskell IDE Engine

See official documentation

In addition, you can generate (and re-generate after changes to stack.yaml) a hie.yaml configuration file with

make hie.yaml

6.2. Emacs {#DevEmacs}

6.2.1. Jump-to-definition {#DevEmacsJump}

Jump-to-definition is possible with hasktags. First you need to install it and make sure it’s on your PATH (if you don’t want hasktags to be on your PATH, do M-x customize-variable haskell-hasktags-path):

stack install hasktags    # or cabal install hasktags

To generate tags, do M-x haskell-mode-generate-tags. You can also add a Git hook to regenerate tags on checkout:

echo "hasktags -e -x ." > .git/hooks/post-checkout
chmod +x .git/hooks/post-checkout

To jump to an identifier, press M-.. You can also do C-u M-x xref-find-definitions to get interactive search through identifiers. Press M-, to return to where you were before the jump.

Jump-to-definition is case-insensitive by default, which is probably not what you want. To change that, do M-x customize-variable tags-case-fold-search.

By default hasktags only generates tags for the current package. The Wire backend is composed of many packages, and it’s useful to be able to jump to any identifier in wire-server. One way to do it is to setup Emacs to check if there’s a Projectile project that the current directory belongs to, and if so, override the “current package” default.

Install the projectile package for Emacs and do M-x projectile-add-known-project <path to wire-server>. Then add the following snippet to your init.el:

(require 'haskell)
(require 'projectile)

;; When inside a project, even if there is a cabal file in the current
;; folder, use the project folder to generate tags. This is useful for
;; projects with several services or subprojects.
(defadvice haskell-cabal--find-tags-dir (around project-tags act)
  (setq ad-return-value
    (if (projectile-project-root)

6.2.2. Haskell Language Server

To use HLS bundled in direnv setup, here is a sample .dir-locals.el that can be put in the root directory of the project:

((haskell-mode . ((haskell-completion-backend . lsp)
                  (lsp-haskell-server-path . "/home/haskeller/code/wire-server/hack/bin/nix-hls.sh")

6.2.3. Ormolu integration

There are make targets format, formatf, formatc to re-format or check the entire repository. This takes about 10 seconds.

Emacs integration is linked here.

6.3. Vim {#DevVim}

6.3.1. hie (Haskell IDE engine) integration

6.3.2. ormolu integration

There are make targets format, formatf, formatc to re-format or check the entire repository. This takes about 10 seconds.

Vim integration is linked here.

If you use sdiehl’s module, you you need to collect the language extensions from package-defaults.yaml:

    let g:ormolu_options = ["--ghc-opt -XAllowAmbiguousTypes --ghc-opt -XBangPatterns --ghc-opt -XConstraintKinds --ghc-opt -XDataKinds --ghc-opt -XDefaultSignatures --ghc-opt -XDerivingStrategies --ghc-opt -XDeriveFunctor --ghc-opt -XDeriveGeneric --ghc-opt -XDeriveLift --ghc-opt -XDeriveTraversable --ghc-opt -XEmptyCase --ghc-opt -XFlexibleContexts --ghc-opt -XFlexibleInstances --ghc-opt -XFunctionalDependencies --ghc-opt -XGADTs --ghc-opt -XInstanceSigs --ghc-opt -XKindSignatures --ghc-opt -XLambdaCase --ghc-opt -XMultiParamTypeClasses --ghc-opt -XMultiWayIf --ghc-opt -XNamedFieldPuns --ghc-opt -XNoImplicitPrelude --ghc-opt -XOverloadedStrings --ghc-opt -XPackageImports --ghc-opt -XPatternSynonyms --ghc-opt -XPolyKinds --ghc-opt -XQuasiQuotes --ghc-opt -XRankNTypes --ghc-opt -XScopedTypeVariables --ghc-opt -XStandaloneDeriving --ghc-opt -XTemplateHaskell --ghc-opt -XTupleSections --ghc-opt -XTypeApplications --ghc-opt -XTypeFamilies --ghc-opt -XTypeFamilyDependencies --ghc-opt -XTypeOperators --ghc-opt -XUndecidableInstances --ghc-opt -XViewPatterns"]

If you want to be playful, you can look at how tools/ormolu.sh collects the language extensions automatically and see if you can get it to work here.

6.4. VSCode

The project can be loaded into the Haskell Language Server. This gives type checking, code completion, HLint hints, formatting with Ormolu, lookup of definitions and references, etc.. All needed dependencies (like the haskell-language-server and stack binaries) are provided by shell.nix.

Setup steps:

  • Install the plugins Haskell (Haskell Language Server support), Haskell Syntax and Nix Environment Selector

  • Generate the hie.yaml file: make hie.yaml

  • Select the nix environment from shell.nix with the command Nix-Env: Select environment.

  • Reload the window as proposed by the Nix Environment Selector plugin

An alternative way to make these dependencies accessible to VSCode is to start it in the direnv environment. I.e. from a shell that’s current working directory is in the project. The drawbacks of this approach are that it only works locally (not on a remote connection) and one VSCode process needs to be started per project.