Atom Pulsar Language Server Protocol Client (Forked!)

This repo was moved from atom/atom-languageclient

Provide integration support for adding Language Server Protocol servers to Pulsar.

I followed a link from a package README. What functionality does this provide?

If a link from some package’s README file has brought you here, it means that package uses atom-languageclient as a dependency. This library knows how to communicate to language servers (“brains” that know how to analyze code in ways that are useful to code editors) and deliver those smarts to Pulsar in the ways that Pulsar expects.

In Pulsar, there is often a division between “consumer” packages and “provider” packages. For instance, the built-in autocomplete-plus package knows how to show users an autocomplete menu, but doesn’t know what to suggest while you type. It relies on other packages to act as data sources and feed it suggestion information on the fly.

The contracts between “provider” packages and “consumer” packages are called services. The services used by built-in packages (and by popular community packages) are de facto standards. atom-languageclient makes it so that one language server “brain” can act as a provider for a large handful of these services at once.

Capabilities vary; some language servers support lots of tasks, and others support only a few. But here are some things that a language server can do, and the parts of Pulsar that this package talks to to make them happen:

autocomplete-plus (builtin Pulsar package)
- See autocompletion options as you type
symbols-view (builtin Pulsar package)
- View and filter a list of symbols in the current file (function names, class names, etc.)
- View and filter a list of symbols across all files in the project
- Jump to the definition of the symbol under the cursor
linter and linter-ui-default
- View diagnostic messages as you type (syntax errors, stylistic suggestions, etc.)
intentions
- Open a menu to view possible code actions for a diagnostic message
- Open a menu to view possible code actions for the file at large
pulsar-outline-view
- View a hierarchical list of the current file’s symbols
pulsar-refactor
- Perform project-wide renaming of variables, methods, classes, types, etc.
pulsar-find-references
- Place the cursor inside of a token to highlight other usages of that token
- Place the cursor inside of a token, then view a find-and-replace-style “results” panel containing all usages of that token across your project
atom-ide-definitions
- Jump to the definition of the symbol under the cursor
atom-ide-datatip
- Hover over a symbol to see any related documentation, including method signatures
atom-ide-signature-help
- View a function’s parameter signature as you type its arguments
atom-ide-code-format
- Invoke on a buffer (or a subset of your buffer) to reformat your code according to the language server’s settings

What’s different from mainline `atom-languageclient`?

Here are a few of the notable features added in this fork:

Symbol search within files and across projects, plus “Go to Reference” support, via the builtin symbols-view package
- Ability to customize/ignore symbols before they’re shown to the user
Deeper integration with linter:
- Possible solutions for linting issues appear in an intentions menu
- Ability to customize/ignore diagnostic messages before they’re shown to the user
Using the intentions package for code actions:
- Ability to invoke the intentions:show command anywhere in the buffer and receive code action suggestions
Removed dependency on the zadeh library in favor of Pulsar’s built-in fuzzy-matcher (zadeh doesn’t have an Apple Silicon pre-build, so this was causing headaches for some users)
- If the built-in fuzzy-matcher somehow isn’t present, we fall back to fuzzaldrin (written in pure JS)

More features are planned.

Background

Language Server Protocol (LSP) is a JSON-RPC based mechanism whereby a client (IDE) may connect to an out-of-process server that can provide rich analysis, refactoring and interactive features for a given programming language.

Implementation

This npm package can be used by Atom package authors wanting to integrate LSP-compatible language servers with Atom. It provides:

Conversion routines between Atom and LSP types
A TypeScript wrapper around JSON-RPC for v3 of the LSP protocol
All necessary TypeScript input and return structures for LSP, notifications etc.
A number of adapters to translate communication between Atom/Atom-IDE and the LSP's capabilities
Automatic wiring up of adapters based on the negotiated capabilities of the language server
Helper functions for downloading additional non-npm dependencies

Capabilities

The language server protocol consists of a number of capabilities. Some of these already have a counterpoint we can connect up to today while others do not. The following table shows each capability in v2 and how it is exposed via Pulsar:

Capability	Atom interface
window/showMessage	`notifications` (builtin)
window/showMessageRequest	`notifications` (builtin)
window/logMessage	TBD
telemetry/event	Ignored
workspace/didChangeWatchedFiles	Pulsar core
textDocument/publishDiagnostics	`linter` v2 push/indie
textDocument/completion	`autocomplete-plus` (builtin)
completionItem/resolve	`autocomplete-plus` (builtin)
textDocument/hover	`atom-ide-datatip`
textDocument/signatureHelp	`atom-ide-signature-help`
textDocument/definition	`atom-ide-definitions` / `symbols-view`
textDocument/findReferences	`pulsar-find-references`
textDocument/documentHighlight	TBD
textDocument/documentSymbol	`symbols-view` / `atom-ide-outline` / `pulsar-outline-view`
workspace/symbol	`symbols-view`
textDocument/codeAction	`intentions`
textDocument/codeLens	TBD
textDocument/formatting	`atom-ide-code-format`
textDocument/rangeFormatting	`atom-ide-code-format`
textDocument/onTypeFormatting	TBD
textDocument/onSaveFormatting	TBD
textDocument/prepareCallHierarchy	TBD
textDocument/rename	`pulsar-refactor`
textDocument/didChange	Pulsar core
textDocument/didOpen	Pulsar core
textDocument/didSave	Pulsar core
textDocument/willSave	Pulsar core
textDocument/didClose	Pulsar core

(atom-ide-ui references removed, since it is currently incompatible with Pulsar)

Developing packages

The underlying JSON-RPC communication is handled by the vscode-jsonrpc npm module.

Minimal example (Nodejs-compatible LSP exe)

A minimal implementation can be illustrated by the Omnisharp package here which has only npm-managed dependencies, and the LSP is a JavaScript file. You simply provide the scope name, language name and server name as well as start your process and AutoLanguageClient takes care of interrogating your language server capabilities and wiring up the appropriate services within Atom to expose them.

const { AutoLanguageClient } = require("atom-languageclient")

class CSharpLanguageClient extends AutoLanguageClient {
  getGrammarScopes() {
    return ["source.cs"]
  }
  getLanguageName() {
    return "C#"
  }
  getServerName() {
    return "OmniSharp"
  }

  startServerProcess() {
    return super.spawnChildNode([require.resolve("omnisharp-client/languageserver/server")])
  }
}

module.exports = new CSharpLanguageClient()

You can get this code packaged up with the necessary package.json etc. from the ide-csharp provides C# support via Omnisharp (node-omnisharp) repo.

Note that you will also need to add various entries to the providedServices and consumedServices section of your package.json (for now). You can obtain these entries here.

Minimal example (General LSP exe)

If the LSP is a general executable (not a JavaScript file), you should use spawn inside startServerProcess.

const { AutoLanguageClient } = require("atom-languageclient")

class DLanguageClient extends AutoLanguageClient {
  getGrammarScopes() {
    return ["source.d"]
  }
  getLanguageName() {
    return "D"
  }
  getServerName() {
    return "serve-d"
  }

  startServerProcess(projectPath) {
    return super.spawn(
      "serve-d", // the `name` or `path` of the executable
      // if the `name` is provided it checks `bin/platform-arch/exeName` by default, and if doesn't exists uses the `exeName` on the PATH
      [], // args passed to spawn the exe
      { cwd: projectPath } // child process spawn options
    )
  }
}

module.exports = new DLanguageClient()

Using other connection types

The default connection type is stdio however both ipc and sockets are also available.

IPC

To use ipc simply return ipc from getConnectionType(), e.g.

class ExampleLanguageClient extends AutoLanguageClient {
  getGrammarScopes() {
    return ["source.js", "javascript"]
  }
  getLanguageName() {
    return "JavaScript"
  }
  getServerName() {
    return "JavaScript Language Server"
  }

  getConnectionType() {
    return "ipc"
  }

  startServerProcess() {
    const startServer = require.resolve("@example/js-language-server")
    return super.spawnChildNode([startServer, "--node-ipc"], {
      stdio: [null, null, null, "ipc"],
    })
  }
}

Sockets

Sockets are a little more complex because you need to allocate a free socket. The ide-php package contains an example of this.

Debugging

Atom-LanguageClient can log all sent and received messages nicely formatted to the Developer Tools Console within Atom. To do so simply enable it with atom.config.set('core.debugLSP', true), e.g.

Tips

Some more elaborate scenarios can be found in the ide-java package which includes:

Downloading and unpacking non-npm dependencies (in this case a .tar.gz containing JAR files)
Platform-specific start-up configuration
Wiring up custom extensions to the protocol (language/status to Atom Status-Bar, language/actionableNotification to Atom Notifications)

Available packages

Right now we have the following experimental Atom LSP packages in development. They are mostly usable but are missing some features that either the LSP server doesn't support or expose functionality that is as yet unmapped to Atom (TODO and TBD in the capabilities table above).

Official packages

ide-csharp provides C# support via Omnisharp (node-omnisharp)
ide-flowtype provides Flow support via Flow Language Server
ide-java provides Java support via Java Eclipse JDT
ide-typescript provides TypeScript and Javascript support via SourceGraph Typescript Language Server

Community packages

Our full list of Atom IDE packages includes the community packages.

Other language servers

Additional LSP servers that might be of interest to be packaged with this for Atom can be found at LangServer.org

Contributing

Running from source

If you want to run from source you will need to perform the following steps (you will need node and npm intalled):

Check out the source
From the source folder type npm link to build and link
From the folder where your package lives type npm link atom-languageclient

If you want to switch back to the production version of atom-languageclient type npm unlink atom-languageclient from the folder where your package lives.

Before sending a PR

We have various unit tests and some linter rules - you can run both of these locally using npm test to ensure your CI will get a clean build.

Guidance

Always feel free to help out! Whether it's filing bugs and feature requests or working on some of the open issues, Atom's contributing guide will help get you started while the guide for contributing to packages has some extra information.

License

MIT License. See the license for more details.

savetheclocktower/atom-languageclient