Awesome
ghcide
- A library for building Haskell IDE tooling
Note: ghcide
was previously called hie-core
.
Our vision is that you should build an IDE by combining:
hie-bios
for determining where your files are, what are their dependencies, what extensions are enabled and so on;ghcide
(i.e. this library) for defining how to type check, when to type check, and producing diagnostic messages;- A bunch of plugins that haven't yet been written, e.g.
hie-hlint
andhie-ormolu
, to choose which features you want; haskell-lsp
for sending those messages to a Language Server Protocol (LSP) server;- An extension for your editor. We provide a VS Code extension as
extension
in this directory, although the components work in other LSP editors too (see below for instructions using Emacs).
There are more details about our approach in this blog post.
Features
ghcide
already exports the following features via the lsp protocol:
Feature | LSP name |
---|---|
Display error messages (parse errors, typecheck errors, etc.) and enabled warnings. | diagnostics |
Go to definition in local package | definition |
Display type and source module of values | hover |
Remove redundant imports, replace suggested typos for values and module imports, fill type holes, insert missing type signatures, add suggested ghc extensions | codeAction (quickfix) |
Limitations to Multi-Component support
ghcide
supports loading multiple components into the same session so that
features such as go-to definition work across components. However, there are
some limitations to this.
- You will get much better results currently manually specifying the hie.yaml file. Until tools like cabal and stack provide the right interface to support multi-component projects, it is always advised to specify explicitly how your project partitions.
- Cross-component features only work if you have loaded at least one file from each component.
- There is a known issue where if you have three components, such that A depends on B which depends on C then if you load A and C into the session but not B then under certain situations you can get strange errors about a type coming from two different places. See this repo for a simple reproduction of the bug.
Using it
Install ghcide
With Nix
Note that you need to compile ghcide
with the same ghc
as the project you are working on.
-
If the
ghc
you are using matches the version (or better is) fromnixpkgs
it‘s easiest to use theghcide
fromnixpkgs
. You can do so vianix-env -iA haskellPackages.ghcide
or e.g. including
pkgs.haskellPackages.ghcide
in your projectsshell.nix
. Depending on yournixpkgs
channel that might not be the newestghcide
, though. -
If your
ghc
does not match nixpkgs you should try the ghcide-nix repository which provides aghcide
via thehaskell.nix
infrastructure.
With Cabal or Stack
First install the ghcide
binary using stack
or cabal
, e.g.
git clone https://github.com/haskell/ghcide.git
cd ghcide
cabal install
orstack install
(and make sure~/.local/bin
is on your$PATH
)
It's important that ghcide
is compiled with the same compiler you use to build your projects.
Test ghcide
Next, check that ghcide
is capable of loading your code. Change to the project directory and run ghcide
, which will try and load everything using the same code as the IDE, but in a way that's much easier to understand. For example, taking the example of shake
, running ghcide
gives some error messages and warnings before reporting at the end:
Files that failed:
* .\model\Main.hs
* .\model\Model.hs
* .\model\Test.hs
* .\model\Util.hs
* .\output\docs\Main.hs
* .\output\docs\Part_Architecture_md.hs
Completed (152 worked, 6 failed)
Of the 158 files in Shake, as of this moment, 152 can be loaded by the IDE, but 6 can't (error messages for the reasons they can't be loaded are given earlier). The failing files are all prototype work or test output, meaning I can confidently use Shake.
The ghcide
executable mostly relies on hie-bios
to do the difficult work of setting up your GHC environment. If it doesn't work, see the hie-bios
manual to get it working. My default fallback is to figure it out by hand and create a direct
style hie.yaml
listing the command line arguments to load the project.
If you can't get ghcide
working outside the editor, see this setup troubleshooting guide. Once you have got ghcide
working outside the editor, the next step is to pick which editor to integrate with.
Optimal project setup
ghcide
has been designed to handle projects with hundreds or thousands of modules. If ghci
can handle it, then ghcide
should be able to handle it. The only caveat is that this currently requires GHC >= 8.6, and that the first time a module is loaded in the editor will trigger generation of support files in the background if those do not already exist.
Configuration
ghcide
accepts the following lsp configuration options:
{
// When to check the dependents of a module
// AlwaysCheck means retypechecking them on every change
// CheckOnSave means dependent/parent modules will only be checked when you save
// "CheckOnSaveAndClose" by default
checkParents : "NeverCheck" | "CheckOnClose" | "CheckOnSaveAndClose" | "AlwaysCheck" | ,
// Whether to check the entire project on initial load
// true by default
checkProject : boolean
}
Using with VS Code
You can install the VSCode extension from the VSCode marketplace.
Using with Atom
You can follow the instructions to install with apm
.
Using with Sublime Text
- Install LSP
- Press Ctrl+Shift+P or Cmd+Shift+P in Sublime Text and search for Preferences: LSP Settings, then paste these settings
{
"clients":
{
"ghcide":
{
"enabled" : true,
"languageId": "haskell",
"command" : ["ghcide", "--lsp"],
"scopes" : ["source.haskell"],
"syntaxes" : ["Packages/Haskell/Haskell.sublime-syntax"]
}
}
}
Using with Emacs
If you don't already have MELPA package installation configured, visit MELPA getting started page to get set up. Then, install use-package
.
Now you have a choice of two different Emacs packages which can be used to communicate with the ghcide
LSP server:
lsp-ui
eglot
(requires Emacs 26.1+)
In each case, you can enable support by adding the shown lines to your .emacs
:
lsp-ui
;; LSP
(use-package flycheck
:ensure t
:init
(global-flycheck-mode t))
(use-package yasnippet
:ensure t)
(use-package lsp-mode
:ensure t
:hook (haskell-mode . lsp)
:commands lsp)
(use-package lsp-ui
:ensure t
:commands lsp-ui-mode)
(use-package lsp-haskell
:ensure t
:config
(setq lsp-haskell-process-path-hie "ghcide")
(setq lsp-haskell-process-args-hie '())
;; Comment/uncomment this line to see interactions between lsp client/server.
;;(setq lsp-log-io t)
)
eglot
(use-package eglot
:ensure t
:config
(add-to-list 'eglot-server-programs '(haskell-mode . ("ghcide" "--lsp"))))
Using with Vim/Neovim
LanguageClient-neovim
Install LanguageClient-neovim
Add this to your vim config:
let g:LanguageClient_rootMarkers = ['*.cabal', 'stack.yaml']
let g:LanguageClient_serverCommands = {
\ 'rust': ['rls'],
\ 'haskell': ['ghcide', '--lsp'],
\ }
Refer to :he LanguageClient
for more details on usage and configuration.
vim-lsp
Install vim-lsp.
Add this to your vim config:
au User lsp_setup call lsp#register_server({
\ 'name': 'ghcide',
\ 'cmd': {server_info->['/your/path/to/ghcide', '--lsp']},
\ 'whitelist': ['haskell'],
\ })
To verify it works move your cursor over a symbol and run :LspHover
.
coc.nvim
Install coc.nvim
Add this to your coc-settings.json (which you can edit with :CocConfig):
{
"languageserver": {
"haskell": {
"command": "ghcide",
"args": [
"--lsp"
],
"rootPatterns": [
".stack.yaml",
".hie-bios",
"BUILD.bazel",
"cabal.config",
"package.yaml"
],
"filetypes": [
"hs",
"lhs",
"haskell"
]
}
}
}
Here's a nice article on setting up neovim and coc: Vim and Haskell in 2019 (this is actually for haskell-ide, not ghcide)
Here is a Docker container that pins down the build and configuration for Neovim and ghcide on a minimal Debian 10 base system: docker-ghcide-neovim.
SpaceVim
In the autocomplete
layer, add the autocomplete_method
option to force the use of coc
:
[[layers]]
name = 'autocomplete'
auto-completion-return-key-behavior = "complete"
auto-completion-tab-key-behavior = "smart"
[options]
autocomplete_method = "coc"
Add this to your coc-settings.json (which you can edit with :CocConfig):
{
"languageserver": {
"haskell": {
"command": "ghcide",
"args": [
"--lsp"
],
"rootPatterns": [
".stack.yaml",
".hie-bios",
"BUILD.bazel",
"cabal.config",
"package.yaml"
],
"filetypes": [
"hs",
"lhs",
"haskell"
]
}
}
}
This example above describes a setup in which ghcide
is installed
using stack install ghcide
within a project.
Using with Kakoune
Install kak-lsp.
Change kak-lsp.toml
to include this:
[language.haskell]
filetypes = ["haskell"]
roots = ["Setup.hs", "stack.yaml", "*.cabal", "cabal.project", "hie.yaml"]
command = "ghcide"
args = ["--lsp"]
Hacking on ghcide
To build and work on ghcide
itself, you can use Stack or cabal, e.g.,
running stack test
will execute the test suite.
If you are using Windows, you should disable the auto.crlf
setting and configure your editor to use LF line endings, directly or making it use the existing .editor-config
.
If you are chasing down test failures, you can use the tasty-rerun feature by running tests as
stack --stack-yaml=stack84.yaml test --test-arguments "--rerun"
This writes a log file called .tasty-rerun-log
of the failures, and only runs those.
See the tasty-rerun documentation for other options.
If you are touching performance sensitive code, take the time to run a differential
benchmark between HEAD and upstream using the benchHist script. The configuration in
bench/hist.yaml
is setup to do this by default assuming upstream is
origin/master
. Run the benchmarks with stack
:
export STACK_YAML=...
stack bench
It should take around 15 minutes and the results will be stored in the bench-hist
folder.
To interpret the results, see the comments in the bench/hist/Main.hs
module.
Building the extension
For development, you can also the VSCode extension from this repository (see
https://code.visualstudio.com/docs/setup/mac for details on adding
code
to your $PATH
):
cd extension/
npm ci
npm run vscepackage
code --install-extension ghcide-0.0.1.vsix
Now opening a .hs
file should work with ghcide
.
History and relationship to other Haskell IDE's
The teams behind this project and the haskell-ide-engine
have agreed to join forces under the haskell-language-server
project, see the original announcement. The technical work is ongoing, with the likely model being that this project serves as the core, while plugins and integrations are kept in the haskell-language-server
project.
The code behind ghcide
was originally developed by Digital Asset as part of the DAML programming language. DAML is a smart contract language targeting distributed-ledger runtimes, based on GHC with custom language extensions. The DAML programming language has an IDE, and work was done to separate off a reusable Haskell-only IDE (what is now ghcide
) which the DAML IDE then builds upon. Since that time, there have been various non-Digital Asset contributors, in addition to continued investment by Digital Asset. The project has been handed over to Haskell.org as of September 2020.
The Haskell community has various IDE choices, but the one that had been gathering momentum is haskell-ide-engine
. Our project owes a debt of gratitude to the haskell-ide-engine
. We reuse libraries from their ecosystem, including hie-bios
(a likely future environment setup layer in haskell-ide-engine
), haskell-lsp
and lsp-test
(the haskell-ide-engine
LSP protocol pieces). We make heavy use of their contributions to GHC itself, in particular the work to make GHC take string buffers rather than files.
The best summary of the architecture of ghcide
is available this talk (slides), given at MuniHac 2019. However, since that talk the project has renamed from hie-core
to ghcide
, and the repo has moved to this location.