Language Server Protocol (LSP) implementation for TypeScript using tsserver

Usage no npm install needed!

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  import elasticTypescriptLanguageServer from 'https://cdn.skypack.dev/@elastic/typescript-language-server';


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TypeScript Language Server

Language Server Protocol implementation for TypeScript wrapping tsserver.


Based on concepts and ideas from https://github.com/prabirshrestha/typescript-language-server and originally maintained by TypeFox

Maintained by a community of contributors like you


npm install -g typescript-language-server

Running the language server

typescript-language-server --stdio

CLI Options

  Usage: typescript-language-server [options]


    -V, --version                          output the version number
    --stdio                                use stdio (required option)
    --log-level <log-level>                A number indicating the log level (4 = log, 3 = info, 2 = warn, 1 = error). Defaults to `3`.
    --tsserver-log-file <tsServerLogFile>  Specify a tsserver log file. example: --tsserver-log-file=ts-logs.txt
    --tsserver-log-verbosity <verbosity>   Specify tsserver log verbosity (off, terse, normal, verbose). Defaults to `normal`. example: --tsserver-log-verbosity=verbose
    --tsserver-path <path>                 Specify path to tsserver directory. example: --tsserver-path=/Users/me/typescript/lib/
    -h, --help                             output usage information

Note: The path passed to --tsserver-path should ideally be a path to the /.../typescript/lib/ directory and not to the shell script /.../node_modules/.bin/tsserver or tsserver. Though for backward-compatibility reasons, the server will try to do the right thing even when passed a path to the shell script.


The language server accepts various settings through the initializationOptions object passed through the initialize request. Refer to your LSP client's documentation on how to set these. Here is the list of supported options:

Setting Type Description
hostInfo string Information about the host, for example "Emacs 24.4" or "Sublime Text v3075". Default: undefined
disableAutomaticTypingAcquisition boolean Disables tsserver from automatically fetching missing type definitions (@types packages) for external modules.
logVerbosity string The verbosity level of the information printed in the log by tsserver. Accepts values: "off", "terse", "normal", "requesttime", "verbose". Default: undefined ("off").
maxTsServerMemory number The maximum size of the V8's old memory section in megabytes (for example 4096 means 4GB). The default value is dynamically configured by Node so can differ per system. Increase for very big projects that exceed allowed memory usage. Default: undefined
npmLocation string Specifies the path to the NPM executable used for Automatic Type Acquisition.
plugins object[] An array of { name: string, location: string } objects for registering a Typescript plugins. Default: []
preferences object Preferences passed to the Typescript (tsserver) process. See below for more info.

The preferences object is an object specifying preferences for the internal tsserver process. Those options depend on the version of Typescript used but at the time of writing Typescript v4.4.3 contains these options:

interface UserPreferences {
    disableSuggestions: boolean;
    quotePreference: "auto" | "double" | "single";
     * If enabled, TypeScript will search through all external modules' exports and add them to the completions list.
     * This affects lone identifier completions but not completions on the right hand side of `obj.`.
    includeCompletionsForModuleExports: boolean;
     * Enables auto-import-style completions on partially-typed import statements. E.g., allows
     * `import write|` to be completed to `import { writeFile } from "fs"`.
    includeCompletionsForImportStatements: boolean;
     * Allows completions to be formatted with snippet text, indicated by `CompletionItem["isSnippet"]`.
    includeCompletionsWithSnippetText: boolean;
     * If enabled, the completion list will include completions with invalid identifier names.
     * For those entries, The `insertText` and `replacementSpan` properties will be set to change from `.x` property access to `["x"]`.
    includeCompletionsWithInsertText: boolean;
     * Unless this option is `false`, or `includeCompletionsWithInsertText` is not enabled,
     * member completion lists triggered with `.` will include entries on potentially-null and potentially-undefined
     * values, with insertion text to replace preceding `.` tokens with `?.`.
    includeAutomaticOptionalChainCompletions: boolean;
     * If enabled, completions for class members (e.g. methods and properties) will include
     * a whole declaration for the member.
     * E.g., `class A { f| }` could be completed to `class A { foo(): number {} }`, instead of
     * `class A { foo }`.
     * @since 4.5.2
     * @default true
    includeCompletionsWithClassMemberSnippets: boolean;
     * Allows import module names to be resolved in the initial completions request.
     * @default false
    allowIncompleteCompletions: boolean;
    importModuleSpecifierPreference: "shortest" | "project-relative" | "relative" | "non-relative";
    /** Determines whether we import `foo/index.ts` as "foo", "foo/index", or "foo/index.js" */
    importModuleSpecifierEnding: "auto" | "minimal" | "index" | "js";
    allowTextChangesInNewFiles: boolean;
    lazyConfiguredProjectsFromExternalProject: boolean;
    providePrefixAndSuffixTextForRename: boolean;
    provideRefactorNotApplicableReason: boolean;
    allowRenameOfImportPath: boolean;
    includePackageJsonAutoImports: "auto" | "on" | "off";
     * Preferred style for JSX attribute completions:
     * - `"auto"` - Insert `={}` or `=\"\"` after attribute names based on the prop type.
     * - `"braces"` - Insert `={}` after attribute names.
     * - `"none"` - Only insert attribute names.
     * @since 4.5.2
     * @default 'auto'
    jsxAttributeCompletionStyle: "auto" | "braces" | "none";
    displayPartsForJSDoc: boolean;
    generateReturnInDocTemplate: boolean;

From the preferences options listed above, this server explicilty sets the following options (all other options use their default values):

    allowIncompleteCompletions: true,
    allowRenameOfImportPath: true,
    allowTextChangesInNewFiles: true,
    displayPartsForJSDoc: true,
    generateReturnInDocTemplate: true,
    includeAutomaticOptionalChainCompletions: true,
    includeCompletionsForImportStatements: true,
    includeCompletionsForModuleExports: true,
    includeCompletionsWithClassMemberSnippets: true,
    includeCompletionsWithInsertText: true,
    includeCompletionsWithSnippetText: true,
    jsxAttributeCompletionStyle: "auto",


Some of the preferences can be controlled through the workspace/didChangeConfiguration notification. Below is a list of supported options that can be passed. Note that the settings are specified separately for the typescript and javascript files so [language] can be either javascript or typescript.

// Formatting preferences
[language].format.baseIndentSize: number;
[language].format.convertTabsToSpaces: boolean;
[language].format.indentSize: number;
[language].format.indentStyle: 'None' | 'Block' | 'Smart';
[language].format.insertSpaceAfterCommaDelimiter: boolean;
[language].format.insertSpaceAfterConstructor: boolean;
[language].format.insertSpaceAfterFunctionKeywordForAnonymousFunctions: boolean;
[language].format.insertSpaceAfterKeywordsInControlFlowStatements: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingEmptyBraces: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingJsxExpressionBraces: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingNonemptyBraces: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingNonemptyBrackets: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis: boolean;
[language].format.insertSpaceAfterOpeningAndBeforeClosingTemplateStringBraces: boolean;
[language].format.insertSpaceAfterSemicolonInForStatements: boolean;
[language].format.insertSpaceAfterTypeAssertion: boolean;
[language].format.insertSpaceBeforeAndAfterBinaryOperators: boolean;
[language].format.insertSpaceBeforeFunctionParenthesis: boolean;
[language].format.insertSpaceBeforeTypeAnnotation: boolean;
[language].format.newLineCharacter: string;
[language].format.placeOpenBraceOnNewLineForControlBlocks: boolean;
[language].format.placeOpenBraceOnNewLineForFunctions: boolean;
[language].format.semicolons: 'ignore' | 'insert' | 'remove';
[language].format.tabSize: number;
[language].format.trimTrailingWhitespace: boolean;
// Inlay Hints preferences
[language].inlayHints.includeInlayEnumMemberValueHints: boolean;
[language].inlayHints.includeInlayFunctionLikeReturnTypeHints: boolean;
[language].inlayHints.includeInlayFunctionParameterTypeHints: boolean;
[language].inlayHints.includeInlayParameterNameHints: 'none' | 'literals' | 'all';
[language].inlayHints.includeInlayParameterNameHintsWhenArgumentMatchesName: boolean;
[language].inlayHints.includeInlayPropertyDeclarationTypeHints: boolean;
[language].inlayHints.includeInlayVariableTypeHints: boolean;
 * Complete functions with their parameter signature.
 * @default false
completions.completeFunctionCalls: boolean;
// Diagnostics code to be omitted when reporting diagnostics.
// See https://github.com/microsoft/TypeScript/blob/master/src/compiler/diagnosticMessages.json for a full list of valid codes.
diagnostics.ignoredCodes: number[];

Code actions on save

Server announces support for the following code action kinds:

  • source.addMissingImports.ts - adds imports for used but not imported symbols
  • source.fixAll.ts - despite the name, fixes a couple of specific issues: unreachable code, await in non-async functions, incorrectly implemented interface
  • source.removeUnused.ts - removes declared but unused variables
  • source.organizeImports.ts - organizes and removes unused imports

This allows editors that support running code actions on save to automatically run fixes associated with those kinds.

Those code actions, if they apply in the current code, should also be presented in the list of "Source Actions" if the editor exposes those.

The user can enable it with a setting similar to (can vary per-editor):

"codeActionsOnSave": {
    "source.organizeImports.ts": true,
    // or just
    "source.organizeImports": true,

Workspace commands (workspace/executeCommand)

See LSP specification.

Most of the time, you'll execute commands with arguments retrieved from another request like textDocument/codeAction. There are some use cases for calling them manually.

Supported commands:

lsp refers to the language server protocol, tsp refers to the typescript server protocol.

  • _typescript.applyWorkspaceEdit
    type Arguments = [lsp.WorkspaceEdit]
  • _typescript.applyCodeAction
    type Arguments = [tsp.CodeAction]
  • _typescript.applyRefactoring
    type Arguments = [tsp.GetEditsForRefactorRequestArgs]
  • _typescript.organizeImports
    // The "skipDestructiveCodeActions" argument is supported from Typescript 4.4+
    type Arguments = [string] | [string, { skipDestructiveCodeActions?: boolean }]
  • _typescript.applyRenameFile
    type Arguments = [{ sourceUri: string; targetUri: string; }]

Inlay hints (typescript/inlayHints) (experimental)

Supports experimental inline hints.

type Request = {
  textDocument: TextDocumentIdentifier,
  range?: Range,

type Response = {
  inlayHints: InlayHint[];

type InlayHint = {
    text: string;
    position: lsp.Position;
    kind: 'Type' | 'Parameter' | 'Enum';
    whitespaceBefore?: boolean;
    whitespaceAfter?: boolean;

For the request to return any results, some or all of the following options need to be enabled through preferences:

// Not officially part of UserPreferences yet but you can send them along with the UserPreferences just fine:
export interface InlayHintsOptions extends UserPreferences {
    includeInlayParameterNameHints: 'none' | 'literals' | 'all';
    includeInlayParameterNameHintsWhenArgumentMatchesName: boolean;
    includeInlayFunctionParameterTypeHints: boolean;
    includeInlayVariableTypeHints: boolean;
    includeInlayPropertyDeclarationTypeHints: boolean;
    includeInlayFunctionLikeReturnTypeHints: boolean;
    includeInlayEnumMemberValueHints: boolean;

Callers and callees (textDocument/calls) (experimental)

Supports showing callers and calles for a given symbol. If the editor has support for appropriate UI, it can generate a tree of callers and calles for a document.

type Request = {
     * The text document.
    textDocument: TextDocumentIdentifier;
     * The position inside the text document.
    position: Position;
     * Outgoing direction for callees.
     * The default is incoming for callers.
    direction?: CallDirection;

export enum CallDirection {
     * Incoming calls aka. callers
    Incoming = 'incoming',
     * Outgoing calls aka. callees
    Outgoing = 'outgoing',

type Result = {
     * The symbol of a definition for which the request was made.
     * If no definition is found at a given text document position, the symbol is undefined.
    symbol?: DefinitionSymbol;
     * List of calls.
    calls: Call[];

interface Call {
     * Actual location of a call to a definition.
    location: Location;
     * Symbol refered to by this call. For outgoing calls this is a callee,
     * otherwise a caller.
    symbol: DefinitionSymbol;

interface DefinitionSymbol {
     * The name of this symbol.
    name: string;
     * More detail for this symbol, e.g the signature of a function.
    detail?: string;
     * The kind of this symbol.
    kind: SymbolKind;
     * The range enclosing this symbol not including leading/trailing whitespace but everything else
     * like comments. This information is typically used to determine if the the clients cursor is
     * inside the symbol to reveal in the symbol in the UI.
    location: Location;
     * The range that should be selected and revealed when this symbol is being picked, e.g the name of a function.
     * Must be contained by the the `range`.
    selectionRange: Range;

Supported Protocol features

  • textDocument/didChange (incremental)
  • textDocument/didClose
  • textDocument/didOpen
  • textDocument/didSave
  • textDocument/codeAction
  • textDocument/completion (incl. completion/resolve)
  • textDocument/definition
  • textDocument/documentHighlight
  • textDocument/documentSymbol
  • textDocument/executeCommand
  • textDocument/formatting
  • textDocument/rangeFormatting
  • textDocument/hover
  • textDocument/rename
  • textDocument/references
  • textDocument/signatureHelp
  • textDocument/calls (experimental)
  • typescript/inlayHints (experimental, supported from Typescript v4.4.2)
  • workspace/symbol
  • workspace/didChangeConfiguration
  • workspace/executeCommand





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