achirkin/vscode-ghc-simple

Simple GHC (Haskell) integration for VSCode

Simple GHC (Haskell) Integration for VSCode

Simple Haskell support using only GHCi.

Installation

Get vscode-ghc-simple from the Visual Studio Marketplace or run the following in Quick Open:

ext install dramforever.vscode-ghc-simple

Alternatively, if you want the latest and greatest, you can download vsix files from Circle CI. Pick the latest build, and check out the 'Artifacts' tab.

What?

This VSCode extension provides editing enhancements for Haskell development.

Currently implemented features:

1. Diagnostics: Basic squiggles and error messages. Automatic re-checking on save.

   

2. Completion: Crude completion with GHCi's :complete command, with :info lookup. Works okay with imported and top level identifiers.

   

3. Type: View types by selecting in the code. The minimal expression covering the selection will have its type shown. Implemented with :all-types.

   

4. Inline REPL: Add REPL blocks to your code with haddock syntax, either using no spaces before >>> or put it in a comment like -- >>>. Click on the code lens or type Shift+Enter to run a single block, or type Shift+Alt+Enter to run all blocks in a file.

   

5. Definition and usages: See definitions amd references of identifiers. Supports both module level and local identifiers. Implemented with :loc-at and uses. Does not yet support identifiers imported from packages.

   

Why?

Since around GHC 8, the compiler GHC and its interactive REPL GHCi has gained various tooling-related features. These allow for more tooling that communicate with the compiler using text IO and files, instead of a Haskell API. This project aims to explore the possibilities provided by said features, by implementing Haskell tooling within the editor VSCode.

Usage

Basic usage

Install the extension from the marketplace or using the Quick Open command ext install dramforever.vscode-ghc-simple. Open individual Haskell source files or projects, and vscode-ghc-simple will auto-detect the appropriate way to start a GHCi and communicate with it to provide editor tooling. Configuration options can be used to tweak the (see below).

Please note that projects should be opened so that the top-level configuration file (stack.yaml or *.cabal) is at the workspace root. This way the extension can detect the project.

Also note that when the project configuration is changed, the Restart GHCi sessions command needs to be issued manually for changes to take place. Again, see below.

Debugging/issues

The full log of interaction between GHCi and this extension can be found in Output tab for GHC as shown below:

When reporting an issue please also attach relevant log output, ideally (but not necessarily) from a fresh start (Developer: Reload Window command) to reproduction of the bug. You can also check there when things go unexpectedly to see.

Commands

• vscode-ghc-simple.restart: Restart GHCi sessions

  vscode-ghc-simple currently lacks a way of detecting changes of critical configuration files such as stack.yaml or *.cabal. Run this command whenever, had you been running GHCi manually, you would restart it.

Configuration options

• ghcSimple.feature.*: Feature switches

  Some users might want only a subset of the features provided in vscode-ghc-simple. These options can be used to disabled unneeded features.

• ghcSimple.workspaceType: This option is deprecated. See ghcSimple.replCommand and ghcSimple.replScope.

• ghcSimple.replCommand: The command used to start GHCi.

  Configure this to change the command used to start GHCi. $stack_ide_targets will be replaced by the output of stack ide targets. Leave blank for auto detection. When set, overrides the deprecated ghcSimple.workspaceType. If you set this, please also set ghcSimple.replScope to an appropriate value.

• ghcSimple.replScope: The scope of each GHCi session

  Whether GHCi should be started for a project or individual files. Note: This option has no effect when ghcSimple.replCommand is set to empty string for auto detection.

• ghcSimple.startupCommands.*: GHCi Startup commands

  Commands to run at GHCi startup. Configures some common options.

  Two of the command lists are semantically meant to configure GHCi for use by vscode-ghc-simple:

  • all: Commands for all workspaces
  • bare: Commands for standalone files (bare workspaces)

  If you need to add more commands, it's suggested that you do so using the following command list, so that the previous to can be updated as needed in newer versions of vscode-ghc-simple:

  • custom: Custom commands for all workspaces

  Change the options in workspace settings instead of user settings if you want to apply the settings to a workspace locally.

• ghcSimple.useObjectCode: Speed up GHCi reloads using -fobject-code

  Enabled by default. Load everything with -fobject-code first before loading needed files with -fbyte-code. This way only changed files need to be recompiled, which greatly speeds up GHCi on large projects.

• ghcSimple.maxCompletions: Maximum number of completion items to show.

• ghcSimple.inlineRepl.codeLens: Show code lens for GHCi REPL blocks

  Disable this if you don't like 'Run in GHCi' code lens littered around your files. If you disable the inline repl feature using ghcSimple.feature.inlineRepl you will also not see code lens.