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PureScript language server

Node-based Language Server Protocol server for PureScript based on the PureScript IDE server (aka psc-ide / purs ide server). Used as the vscode plugin backend but should be compatible with other Language Server Client implementations.

The language server is a wrapper around the IDE server included as part of the compiler distribution, providing editing assistance and build features according to support available. This means that the server will start its own purs ide server instance to talk to for the project directory it is started in.


  • Completion provider
  • Definition provider
  • Document & workspace symbol providers
  • Hover provider
  • Code action provider
    • Compiler fix suggestions for imports/missing types
  • Build on save (via IDE server "fast rebuild" facility, certain limitations apply)
    • Provides diagnostics
  • Commands
    • Build (full build via purs compile / configured build command) - provides diagnostics
    • Case split
    • Add clause
    • Replace suggestion
    • Add completion import
    • Start IDE server
    • Stop IDE server
    • Restart IDE server
  • Config
    • purescript.*


No arguments. Provides diagnostics.


No arguments. Start IDE server according to configuration.


No arguments. Stop running IDE server.


No arguments. Stop any running IDE server then start a new one according to configuration.


Arguments: identifier, module, document URI.


Arguments: module, qualifier, document URI.


No arguments. Get list of available modules.


Arguments: document URI, replacement, replacement range.

Flex search for identifier.

Arguments: search text.


Arguments: document URI, line, character.


(Used to back the case split command in VS Code UI).

Arguments: document URI, line, character, type.


(Used to back the add clause command in VS Code UI).

Arguments: document URI, line, character.


(Used to back the purescript.typedHole code action triggered in the VS Code UI)

Arguments: hole name, document URI, hole range, PscIde.Command.TypeInfo of chosen replacement option


This LSP implmementation is consumed by vscode and Atom plugins as a node module, and bundled along with those plugins.

To use with another LSP client, you will want to install this either globally or locally for npm, e.g.

npm i -g purescript-language-server

And then use the resulting executable, e.g. purescript-language-server --stdio.

This language server is based on vscode-languageserver-node which means it should support --stdio, --socket=[number], --node-ipc or --pipe methods of communication, see vscode-languageserver-node for details.

Currently you should pass a --config flag followed by a JSON object, or immediately send config on starting the server in the same way VS Code does - this should improve in future.


See config defined in vscode plugin.


To develop (rather than use) this language server

  1. Clone this repo and npm install
  2. Make changes and npm run build
  3. Ensure the built module is picked up by your editor

For 3, if the editor integrates using the node module rather than standalone binary, I suggest using npm link - this will work for atom and vscode at least.

For atom, clone atom-ide-purescript and:

  1. In purescript-language-server run npm link, in atom-ide-purescript run npm link purescript-language-server
  2. In atom-ide-purescript run apm link to pick up local changes
  3. In atom-ide-purescript, run npm run bundle to build the plugin itself
  4. Reload any atom window to pick up changes

For vscode, clone vscode-ide-purescript and:

  1. In purescript-language-server run npm link, in vscode-ide-purescript run npm link purescript-language-server
  2. Open vscode-ide-purescript in vscode and hit F5 to "launch extension"
  3. Use the newly launched Extension Development Host to test language server changes

See vscode plugin repo, atom plugin. Common code via purescript-ide-purescript-core.