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This language client library provides language server protocol support for IntelliJ IDEA and other Jetbrains IDEs.
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LSP4IntelliJ - Language Server Protocol Support for the Jetbrains Plugins

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Lsp4IntelliJ is a client library, which provides language server support for IntelliJ IDEA and other Jetbrains IDEs.

It is designed to be used with any IntelliJ plugin as its language server client to get the features that are based on the language server.

Also, it allows the plugin developers to use language-specific language server protocol extensions via the JSON-RPC protocol.

Table of Contents

How to use

Follow the steps below to use Lsp4IntelliJ in your custom language plugin.

1. Add the lsp4intellij dependency in the build file of the project.

For instrcutions on addding Lsp4IntelliJ as a dependency when using the below build tools, go to jitpack/lsp4intellij.

  • gradle
  • maven
  • sbt

Info: - The Maven publishing process is currently WIP. Thus, the possibility to add LSP4IntelliJ as a dependency will be available soon in the Maven central.

2. Add the language server definition

  1. Instantiate a concrete subclass of the LanguageServerDefinition.

    You can use the following concrete class:

    • RawCommandServerDefinition(string fileExtension, string[] command)

      This definition executes the given command.

      • You can specify multiple extensions for a server by separating them with a comma (e.g., "ts, js").

      • If you want to bind your language server definition only with a specific set of files, you can use that specific file pattern as a regex expression instead of binding with the file extension (e.g., "application*.properties").


      Ballerina Language Server

      new RawCommandServerDefinition("bal", new String[]{"path/to/"});

      BSL Language Server

      String[] command = new String[]{"java","-jar","path/to/language-server.jar"};
      new RawCommandServerDefinition("bsl,os",command);

    Note: All these implementations will use server stdin/stdout to communicate.

  2. To register any of the aforementioned options, implement a preloading activity in your plugin as shown below.

Tip: For other options you can use instead of implementing a preloading activity, go to InteliJ Plugin initialization on startup to)


public class BallerinaPreloadingActivity extends PreloadingActivity {
    IntellijLanguageClient.addServerDefinition(new RawCommandServerDefinition("bal", new String[]{"path/to/"}));

With plugin.xml containing;

<extensions defaultExtensionNs="com.intellij">
    <preloadingActivity implementation="io.ballerina.plugins.idea.preloading.BallerinaPreloadingActivity" 
                        id="io.ballerina.plugins.idea.preloading.BallerinaPreloadingActivity" />

3. Add configurations to the plugin.xml file

  1. Add IntellijLanguageClient as an application component.

  2. Add the following extensions to get the relevant features as listed below.

    • Code completion
      <extensions defaultExtensionNs="com.intellij">
          <completion.contributor implementationClass="org.wso2.lsp4intellij.contributors.LSPCompletionContributor"
                                  id="LSPCompletionContributor" language="any"/>
    • Code Formatting
         <action class="org.wso2.lsp4intellij.actions.LSPReformatAction" id="ReformatCode" use-shortcut-of="ReformatCode"
                 overrides="true" text="Reformat Code"/>
         <action class="org.wso2.lsp4intellij.actions.LSPShowReformatDialogAction" id="ShowReformatFileDialog"
                 use-shortcut-of="ShowReformatFileDialog" overrides="true" text="Show Reformat File Dialog"/>
    • Diagnostics and code actions
      <extensions defaultExtensionNs="com.intellij">
         <localInspection displayName="LSP"
    • Find Usages
          <action class="org.wso2.lsp4intellij.actions.LSPReferencesAction" id="LSPFindUsages">
               <keyboard-shortcut first-keystroke="shift alt F7" keymap="$default"/>
    • Workspace symbols
      <extensions defaultExtensionNs="com.intellij">
          <gotoSymbolContributor implementation="org.wso2.lsp4intellij.contributors.symbol.LSPSymbolContributor"
    • Renaming Support
      <extensions defaultExtensionNs="com.intellij">
          <renameHandler implementation="org.wso2.lsp4intellij.contributors.rename.LSPRenameHandler" 
          id="LSPRenameHandler" order="first"/>
          <renamePsiElementProcessor implementation="org.wso2.lsp4intellij.contributors.rename
           .LSPRenameProcessor" id="LSPRenameProcessor" order="first"/>

Note: You do not need any additional configurations for the other features.

If you have connected to your language server successfully, you will see a green icon at the bottom-right side of your IDE when opening a file that has a registered file extension as shown below.

Tip: You can also click on the icon to see the connected files and the timeouts.


Code Completion

Press the CTRL+SPACE keys to see the completion items list, which depends on your cursor position.(Code completion items will also pop-up auytomatically based on your language-server-specific trigger characters.)

Code Formatting

Navigate to Code->Reformat Code and you will get a dialog to choose whether to format the whole file or the selected range.


To see diagnostics (errors, warnings etc.), hover over them to view the message.

Code Actions

Hover over any diagnostic highlight to view and apply related code actions using the light bulb that pops up as shown below.

Go to Definition

Press the CTRL key while clicking on a symbol to navigate to its definition.

Goto References / Find Usages

You can use CTRL+CLICK or SHIFT+ALT+F7 for a symbol to view the list of its references/usages.

Hover Support

You can hover over an element while pressing the CTRL key to view its documentation if available.

Workspace Symbols

Click Navigate in the top menu, then click Symbol..., and enter the name of the symbol you want to search in the search box that pops up.

Renaming Support

Set the courser to the element which needs to renamed and press CTRL+F6 to trigger the inplace renaming as shown below.

Note - Above features are currently tested only with IntelliJ IDEA and the Ballerina Language Server.

WIP Features

  • Signature Help

User API


The Lsp4IntelliJ language client has default timeout values for LSP-based requests as shown below.

Type Default timeout value(in milliseconds)
Code Actions 2000
Completion 1000
Goto Definition 2000
Execute Command 2000
Formatting 2000
Hover Support 2000
Initialization 10000
References 2000
Shutdown 5000
WillSave 2000

The LspIntelliJ language client provides following methods related to timeout configurations.

  • getTimeouts() - Returns the current timeout values (in milliseconds).


    Map<Timeouts, Integer> timeouts = IntelliJLnaguageClient.getTimeouts();
  • getTimeout(Timeouts timeoutType) - Returns the current timeout value of a given timeout type (in milliseconds).


    int timeout = IntellijLanguageClient.getTimeout(Timeouts.INIT);
  • setTimeouts(Map<Timeouts, Integer> newTimeouts)) - Overrides the default timeout values with a given set of timeout values.


    Map<Timeouts,Integer> newTimeouts = new HashMap<>();
  • setTimeout(Timeouts timeout, int value) - Overrides a specific timeout value with a new one.


    IntellijLanguageClient.setTimeout(Timeouts.INIT, 15000);


The LSP4Intellij code is distributed under the Apache license 2.0.


Lsp4IntelliJ is heavily inspired by the intellij-lsp plugin community. Credits should go to the original author for his astounding work.

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