Language Server Protocol

This document describes version 2.x of the language server protocol. Changes are marked with a change or new bar on the left hand side. Below is a summary of the major changes compared to version 1.0:

Consistent use of properties on request param objects. These properties are now structured like parameters in API's. So for example if an API takes a text document as the first parameter the corresponding parameter literal in the JSON RPC protocol now has a property textDocument.
Consistent support for language identifiers. This means that the language ID is passed to the server via the open notification. Further references to the text document don't transfer this information anymore.
Support for version numbers on documents. The initial version number is sent to the server via the open notification. Document change notification do carry information about version numbers as well.
Support for request cancellation.
Interface naming: using consistent names without I prefix.

The 1.x version of this document can be found here.

Base Protocol

The base protocol consists of a header and a content part (comparable to HTTP). The header and content part are separated by a '\r\n'.

Header Part

The header part consists of header fields. Each header field is comprised of a name and a value, separated by ': ' (a colon and a space). Each header field is terminated by '\r\n'. Considering the last header field and the overall header itself are each terminated with '\r\n', and that at least one header is mandatory, this means that two '\r\n' sequences always immediately precede the content part of a message.

Currently the following header fields are supported:

Header Field Name	Value Type	Description
Content-Length	number	The length of the content part in bytes. This header is required.
Content-Type	string	The mime type of the content part. Defaults to application/vscode-jsonrpc; charset=utf8

The header part is encoded using the 'ascii' encoding. This includes the '\r\n' separating the header and content part.

Content Part

Contains the actual content of the message. The content part of a message uses JSON-RPC to describe requests, responses and notifications. The content part is encoded using the charset provided in the Content-Type field. It defaults to 'utf8', which is the only encoding supported right now.

Example:

Content-Length: ...\r\n
\r\n
{
	"jsonrpc": "2.0",
	"id": 1,
	"method": "textDocument/didOpen", 
	"params": {
		...
	}
}

Base Protocol JSON structures

The following TypeScript definitions describe the base JSON-RPC protocol:

Abstract Message

A general message as defined by JSON-RPC. The language server protocol always uses "2.0" as the jsonrpc version.

interface Message {
	jsonrpc: string;
}

RequestMessage

A request message to describe a request between the client and the server. Every processed request must send a response back to the sender of the request.

interface RequestMessage extends Message {

	/**
	 * The request id.
	 */
	id: number | string;

	/**
	 * The method to be invoked.
	 */
	method: string;

	/**
	 * The method's params.
	 */
	params?: any
}

Response Message

Response Message sent as a result of a request.

interface ResponseMessage extends Message {
	/**
	 * The request id.
	 */
	id: number | string;

	/**
	 * The result of a request. This can be omitted in
	 * the case of an error.
	 */
	result?: any;

	/**
	 * The error object in case a request fails.
	 */
	error?: ResponseError<any>;
}

interface ResponseError<D> {
	/**
	 * A number indicating the error type that occurred.
	 */
	code: number;

	/**
	 * A string providing a short description of the error.
	 */
	message: string;

	/**
	 * A Primitive or Structured value that contains additional
	 * information about the error. Can be omitted.
	 */
	data?: D;
}

export namespace ErrorCodes {
	export const ParseError: number = -32700;
	export const InvalidRequest: number = -32600;
	export const MethodNotFound: number = -32601;
	export const InvalidParams: number = -32602;
	export const InternalError: number = -32603;
	export const serverErrorStart: number = -32099
	export const serverErrorEnd: number = -32000;
}

Notification Message

A notification message. A processed notification message must not send a response back. They work like events.

interface NotificationMessage extends Message {
	/**
	 * The method to be invoked.
	 */
	method: string;

	/**
	 * The notification's params.
	 */
	params?: any
}

Cancellation Support

New: The base protocol now offers support for request cancellation. To cancel a request, a notification message with the following properties is sent:

Notification:

method: '$/cancelRequest'
params: CancelParams defined as follows:

interface CancelParams {
	/**
	 * The request id to cancel.
	 */
	id: number | string;
}

A request that got canceled still needs to return from the server and send a response back. It can not be left open / hanging. This is in line with the JSON RPC protocol that requires that every request sends a response back. In addition it allows for returning partial results on cancel.

Language Server Protocol

The language server protocol defines a set of JSON-RPC request, response and notification messages which are exchanged using the above base protocol. This section starts describing the basic JSON structures used in the protocol. The document uses TypeScript interfaces to describe these. Based on the basic JSON structures, the actual requests with their responses and the notifications are described.

The protocol currently assumes that one server serves one tool. There is currently no support in the protocol to share one server between different tools. Such a sharing would require additional protocol to either lock a document to support concurrent editing.

Basic JSON Structures

Position

Position in a text document expressed as zero-based line and character offset. A position is between two characters like an 'insert' cursor in a editor.

interface Position {
	/**
	 * Line position in a document (zero-based).
	 */
	line: number;

	/**
	 * Character offset on a line in a document (zero-based).
	 */
	character: number;
}

Range

A range in a text document expressed as (zero-based) start and end positions. A range is comparable to a selection in an editor. Therefore the end position is exclusive.

interface Range {
	/**
	 * The range's start position.
	 */
	start: Position;

	/**
	 * The range's end position.
	 */
	end: Position;
}

Location

Represents a location inside a resource, such as a line inside a text file.

interface Location {
	uri: string;
	range: Range;
}

Diagnostic

Represents a diagnostic, such as a compiler error or warning. Diagnostic objects are only valid in the scope of a resource.

interface Diagnostic {
	/**
	 * The range at which the message applies.
	 */
	range: Range;

	/**
	 * The diagnostic's severity. Can be omitted. If omitted it is up to the
	 * client to interpret diagnostics as error, warning, info or hint.
	 */
	severity?: number;

	/**
	 * The diagnostic's code. Can be omitted.
	 */
	code?: number | string;

	/**
	 * A human-readable string describing the source of this
	 * diagnostic, e.g. 'typescript' or 'super lint'.
	 */
	source?: string;

	/**
	 * The diagnostic's message.
	 */
	message: string;
}

The protocol currently supports the following diagnostic severities:

enum DiagnosticSeverity {
	/**
	 * Reports an error.
	 */
	Error = 1,
	/**
	 * Reports a warning.
	 */
	Warning = 2,
	/**
	 * Reports an information.
	 */
	Information = 3,
	/**
	 * Reports a hint.
	 */
	Hint = 4
}

Command

Represents a reference to a command. Provides a title which will be used to represent a command in the UI. Commands are identitifed using a string identifier and the protocol currently doesn't specify a set of well known commands. So executing a command requires some tool extension code.

interface Command {
	/**
	 * Title of the command, like `save`.
	 */
	title: string;
	/**
	 * The identifier of the actual command handler.
	 */
	command: string;
	/**
	 * Arguments that the command handler should be
	 * invoked with.
	 */
	arguments?: any[];
}

TextEdit

A textual edit applicable to a text document.

interface TextEdit {
	/**
	 * The range of the text document to be manipulated. To insert
	 * text into a document create a range where start === end.
	 */
	range: Range;

	/**
	 * The string to be inserted. For delete operations use an
	 * empty string.
	 */
	newText: string;
}

If n TextEdits are applied to a text document all text edits describe changes to the initial document version. Execution wise text edits should applied from the bottom to the top of the text document. Overlapping text edits are not supported.

WorkspaceEdit

A workspace edit represents changes to many resources managed in the workspace.

interface WorkspaceEdit {
   /**
    * Holds changes to existing resources.
    */
   changes: { [uri: string]: TextEdit[]; };
}

TextDocumentIdentifier

Text documents are identified using a URI. On the protocol level, URIs are passed as strings. The corresponding JSON structure looks like this:

interface TextDocumentIdentifier {
	/**
	 * The text document's URI.
	 */
	uri: string;
}

TextDocumentItem

New: An item to transfer a text document from the client to the server.

interface TextDocumentItem {
	/**
	 * The text document's URI.
	 */
	uri: string;

	/**
	 * The text document's language identifier.
	 */
	languageId: string;

	/**
	 * The version number of this document (it will strictly increase after each
	 * change, including undo/redo).
	 */
	version: number;

	/**
	 * The content of the opened text document.
	 */
	text: string;
}

VersionedTextDocumentIdentifier

New: An identifier to denote a specific version of a text document.

interface VersionedTextDocumentIdentifier extends TextDocumentIdentifier {
	/**
	 * The version number of this document.
	 */
	version: number;
}

TextDocumentPositionParams

Changed: Was TextDocumentPosition in 1.0 with inlined parameters

A parameter literal used in requests to pass a text document and a position inside that document.

interface TextDocumentPositionParams {
	/**
	 * The text document.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * The position inside the text document.
	 */
	position: Position;
}

Actual Protocol

This section documents the actual language server protocol. It uses the following format:

a header describing the request
a Request section describing the format of the request sent. The method is a string identifying the request the params are documented using a TypeScript interface
a Response section describing the format of the response. The result item describes the returned data in case of a success. The error.data describes the returned data in case of an error. Please remember that in case of a failure the response already contains an error.code and an error.message field. These fields are only speced if the protocol forces the use of certain error codes or messages. In cases where the server can decide on these values freely they aren't listed here.

Initialize Request

The initialize request is sent as the first request from the client to the server.

Request

method: 'initialize'
params: InitializeParams defined as follows:

interface InitializeParams {
	/**
	 * The process Id of the parent process that started
	 * the server. Is null if the process has not been started by another process.
	 * If the parent process is not alive then the server should exit (see exit notification) its process.
	 */
	processId?: number;

	/**
	 * The rootPath of the workspace. Is null
	 * if no folder is open.
	 */
	rootPath?: string;

	/**
	 * User provided initialization options.
	 */
	initializationOptions?: any;

	/**
	 * The capabilities provided by the client (editor)
	 */
	capabilities: ClientCapabilities;
}

Where ClientCapabilities are currently empty:

interface ClientCapabilities {
}

Response

result: InitializeResult defined as follows:

interface InitializeResult {
	/**
	 * The capabilities the language server provides.
	 */
	capabilities: ServerCapabilities;
}

error.data:

interface InitializeError {
	/**
	 * Indicates whether the client should retry to send the
	 * initilize request after showing the message provided
	 * in the ResponseError.
	 */
	retry: boolean;
}

The server can signal the following capabilities:

/**
 * Defines how the host (editor) should sync document changes to the language server.
 */
enum TextDocumentSyncKind {
	/**
	 * Documents should not be synced at all.
	 */
	None = 0,
	/**
	 * Documents are synced by always sending the full content of the document.
	 */
	Full = 1,
	/**
	 * Documents are synced by sending the full content on open. After that only incremental 
	 * updates to the document are sent.
	 */
	Incremental = 2
}

/**
 * Completion options.
 */
interface CompletionOptions {
	/**
	 * The server provides support to resolve additional information for a completion item.
	 */
	resolveProvider?: boolean;

	/**
	 * The characters that trigger completion automatically.
	 */
	triggerCharacters?: string[];
}

/**
 * Signature help options.
 */
interface SignatureHelpOptions {
	/**
	 * The characters that trigger signature help automatically.
	 */
	triggerCharacters?: string[];
}

/**
 * Code Lens options.
 */
interface CodeLensOptions {
	/**
	 * Code lens has a resolve provider as well.
	 */
	resolveProvider?: boolean;
}

/**
 * Format document on type options
 */
interface DocumentOnTypeFormattingOptions {
	/**
	 * A character on which formatting should be triggered, like `}`.
	 */
	firstTriggerCharacter: string;
	/**
	 * More trigger characters.
	 */
	moreTriggerCharacter?: string[]
}

interface ServerCapabilities {
	/**
	 * Defines how text documents are synced.
	 */
	textDocumentSync?: number;
	/**
	 * The server provides hover support.
	 */
	hoverProvider?: boolean;
	/**
	 * The server provides completion support.
	 */
	completionProvider?: CompletionOptions;
	/**
	 * The server provides signature help support.
	 */
	signatureHelpProvider?: SignatureHelpOptions;
	/**
	 * The server provides goto definition support.
	 */
	definitionProvider?: boolean;
	/**
	 * The server provides find references support.
	 */
	referencesProvider?: boolean;
	/**
	 * The server provides document highlight support.
	 */
	documentHighlightProvider?: boolean;
	/**
	 * The server provides document symbol support.
	 */
	documentSymbolProvider?: boolean;
	/**
	 * The server provides workspace symbol support.
	 */
	workspaceSymbolProvider?: boolean;
	/**
	 * The server provides code actions.
	 */
	codeActionProvider?: boolean;
	/**
	 * The server provides code lens.
	 */
	codeLensProvider?: CodeLensOptions;
	/**
	 * The server provides document formatting.
	 */
	documentFormattingProvider?: boolean;
	/**
	 * The server provides document range formatting.
	 */
	documentRangeFormattingProvider?: boolean;
	/**
	 * The server provides document formatting on typing.
	 */
	documentOnTypeFormattingProvider?: DocumentOnTypeFormattingOptions;
	/**
	 * The server provides rename support.
	 */
	renameProvider?: boolean
}

Shutdown Request

The shutdown request is sent from the client to the server. It asks the server to shut down, but to not exit (otherwise the response might not be delivered correctly to the client). There is a separate exit notification that asks the server to exit.

Request

method: 'shutdown'
params: undefined

Response

result: undefined
error: code and message set in case an exception happens during shutdown request.

Exit Notification

A notification to ask the server to exit its process. The server should exit with success code 0 if the shutdown request has been received before; otherwise with error code 1.

Notification

method: 'exit'
params: undefined

ShowMessage Notification

The show message notification is sent from a server to a client to ask the client to display a particular message in the user interface.

Notification:

method: 'window/showMessage'
params: ShowMessageParams defined as follows:

interface ShowMessageParams {
	/**
	 * The message type. See {@link MessageType}.
	 */
	type: number;

	/**
	 * The actual message.
	 */
	message: string;
}

Where the type is defined as follows:

enum MessageType {
	/**
	 * An error message.
	 */
	Error = 1,
	/**
	 * A warning message.
	 */
	Warning = 2,
	/**
	 * An information message.
	 */
	Info = 3,
	/**
	 * A log message.
	 */
	Log = 4
}

ShowMessage Request

New: The show message request is sent from a server to a client to ask the client to display a particular message in the user interface. In addition to the show message notification the request allows to pass actions and to wait for an answer from the client.

Request:

method: 'window/showMessageRequest'
params: ShowMessageRequestParams defined as follows:

Response:

result: the selected MessageActionItem
error: code and message set in case an exception happens during showing a message.

interface ShowMessageRequestParams {
	/**
	 * The message type. See {@link MessageType}
	 */
	type: number;

	/**
	 * The actual message
	 */
	message: string;

	/**
	 * The message action items to present.
	 */
	actions?: MessageActionItem[];
}

Where the MessageActionItem is defined as follows:

interface MessageActionItem {
	/**
	 * A short title like 'Retry', 'Open Log' etc.
	 */
	title: string;
}

LogMessage Notification

The log message notification is sent from the server to the client to ask the client to log a particular message.

Notification:

method: 'window/logMessage'
params: LogMessageParams defined as follows:

interface LogMessageParams {
	/**
	 * The message type. See {@link MessageType}
	 */
	type: number;

	/**
	 * The actual message
	 */
	message: string;
}

Where type is defined as above.

Telemetry Notification

New: The telemetry notification is sent from the server to the client to ask the client to log a telemetry event.

Notification:

method: 'telemetry/event'
params: 'any'

DidChangeConfiguration Notification

A notification sent from the client to the server to signal the change of configuration settings.

Notification:

method: 'workspace/didChangeConfiguration',
params: DidChangeConfigurationParams defined as follows:

interface DidChangeConfigurationParams {
	/**
	 * The actual changed settings
	 */
	settings: any;
}

DidOpenTextDocument Notification

The document open notification is sent from the client to the server to signal newly opened text documents. The document's truth is now managed by the client and the server must not try to read the document's truth using the document's uri.

Notification:

method: 'textDocument/didOpen'
params: DidOpenTextDocumentParams defined as follows:

interface DidOpenTextDocumentParams {
	/**
	 * The document that was opened.
	 */
	textDocument: TextDocumentItem;
}

DidChangeTextDocument Notification

Changed: The document change notification is sent from the client to the server to signal changes to a text document. In 2.0 the shape of the params has changed to include proper version numbers and language ids.

Notification:

method: 'textDocument/didChange'
params: DidChangeTextDocumentParams defined as follows:

interface DidChangeTextDocumentParams {
	/**
	 * The document that did change. The version number points
	 * to the version after all provided content changes have
	 * been applied.
	 */
	textDocument: VersionedTextDocumentIdentifier;

	/**
	 * The actual content changes.
	 */
	contentChanges: TextDocumentContentChangeEvent[];
}

/**
 * An event describing a change to a text document. If range and rangeLength are omitted
 * the new text is considered to be the full content of the document.
 */
interface TextDocumentContentChangeEvent {
	/**
	 * The range of the document that changed.
	 */
	range?: Range;

	/**
	 * The length of the range that got replaced.
	 */
	rangeLength?: number;

	/**
	 * The new text of the document.
	 */
	text: string;
}

DidCloseTextDocument Notification

The document close notification is sent from the client to the server when the document got closed in the client. The document's truth now exists where the document's uri points to (e.g. if the document's uri is a file uri the truth now exists on disk).

Changed: In 2.0 the params are of type DidCloseTextDocumentParams which contains a reference to a text document.

Notification:

method: 'textDocument/didClose'
params: DidCloseTextDocumentParams defined as follows:

interface DidCloseTextDocumentParams {
	/**
	 * The document that was closed.
	 */
	textDocument: TextDocumentIdentifier;
}

DidSaveTextDocument Notification

New: The document save notification is sent from the client to the server when the document was saved in the client.

method: 'textDocument/didSave'
params: DidSaveTextDocumentParams defined as follows:

interface DidSaveTextDocumentParams {
	/**
	 * The document that was saved.
	 */
	textDocument: TextDocumentIdentifier;
}

DidChangeWatchedFiles Notification

The watched files notification is sent from the client to the server when the client detects changes to files watched by the language client.

Notification:

method: 'workspace/didChangeWatchedFiles'
params: DidChangeWatchedFilesParams defined as follows:

interface DidChangeWatchedFilesParams {
	/**
	 * The actual file events.
	 */
	changes: FileEvent[];
}

Where FileEvents are described as follows:

/**
 * The file event type.
 */
enum FileChangeType {
	/**
	 * The file got created.
	 */
	Created = 1,
	/**
	 * The file got changed.
	 */
	Changed = 2,
	/**
	 * The file got deleted.
	 */
	Deleted = 3
}

/**
 * An event describing a file change.
 */
interface FileEvent {
	/**
	 * The file's URI.
	 */
	uri: string;
	/**
	 * The change type.
	 */
	type: number;
}

PublishDiagnostics Notification

Diagnostics notification are sent from the server to the client to signal results of validation runs.

Notification

method: 'textDocument/publishDiagnostics'
params: PublishDiagnosticsParams defined as follows:

interface PublishDiagnosticsParams {
	/**
	 * The URI for which diagnostic information is reported.
	 */
	uri: string;

	/**
	 * An array of diagnostic information items.
	 */
	diagnostics: Diagnostic[];
}

Completion Request

The Completion request is sent from the client to the server to compute completion items at a given cursor position. Completion items are presented in the IntelliSense user interface. If computing full completion items is expensive, servers can additionally provide a handler for the completion item resolve request ('completionItem/resolve'). This request is sent when a completion item is selected in the user interface. A typically use case is for example: the 'textDocument/completion' request doesn't fill in the documentation property for returned completion items since it is expensive to compute. When the item is selected in the user interface then a 'completionItem/resolve' request is sent with the selected completion item as a param. The returned completion item should have the documentation property filled in.

Changed: In 2.0 the request uses TextDocumentPositionParams with a proper textDocument and position property. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/completion'
params: TextDocumentPositionParams

Response

result: CompletionItem[] | CompletionList

/**
 * Represents a collection of [completion items](#CompletionItem) to be presented
 * in the editor.
 */
interface CompletionList {
	/**
	 * This list it not complete. Further typing should result in recomputing
	 * this list.
	 */
	isIncomplete: boolean;
	/**
	 * The completion items.
	 */
	items: CompletionItem[];
}

interface CompletionItem {
	/**
	 * The label of this completion item. By default
	 * also the text that is inserted when selecting
	 * this completion.
	 */
	label: string;
	/**
	 * The kind of this completion item. Based of the kind
	 * an icon is chosen by the editor.
	 */
	kind?: number;
	/**
	 * A human-readable string with additional information
	 * about this item, like type or symbol information.
	 */
	detail?: string;
	/**
	 * A human-readable string that represents a doc-comment.
	 */
	documentation?: string;
	/**
	 * A string that shoud be used when comparing this item
	 * with other items. When `falsy` the label is used.
	 */
	sortText?: string;
	/**
	 * A string that should be used when filtering a set of
	 * completion items. When `falsy` the label is used.
	 */
	filterText?: string;
	/**
	 * A string that should be inserted a document when selecting
	 * this completion. When `falsy` the label is used.
	 */
	insertText?: string;
	/**
	 * An edit which is applied to a document when selecting
	 * this completion. When an edit is provided the value of
	 * insertText is ignored.
	 */
	textEdit?: TextEdit;
	/**
	 * An optional array of additional text edits that are applied when
	 * selecting this completion. Edits must not overlap with the main edit
	 * nor with themselves.
	 */
	additionalTextEdits?: TextEdit[];
	/**
	 * An optional command that is executed *after* inserting this completion. *Note* that
	 * additional modifications to the current document should be described with the
	 * additionalTextEdits-property.
	 */
	command?: Command;
	/**
	 * An data entry field that is preserved on a completion item between
	 * a completion and a completion resolve request.
	 */
	data?: any
}

Where CompletionItemKind is defined as follows:

/**
 * The kind of a completion entry.
 */
enum CompletionItemKind {
	Text = 1,
	Method = 2,
	Function = 3,
	Constructor = 4,
	Field = 5,
	Variable = 6,
	Class = 7,
	Interface = 8,
	Module = 9,
	Property = 10,
	Unit = 11,
	Value = 12,
	Enum = 13,
	Keyword = 14,
	Snippet = 15,
	Color = 16,
	File = 17,
	Reference = 18
}

error: code and message set in case an exception happens during the completion request.

Completion Item Resolve Request

The request is sent from the client to the server to resolve additional information for a given completion item.

Request

method: 'completionItem/resolve'
params: CompletionItem

Response

result: CompletionItem
error: code and message set in case an exception happens during the completion resolve request.

Hover Request

The hover request is sent from the client to the server to request hover information at a given text document position.

Changed: In 2.0 the request uses TextDocumentPositionParams with a proper textDocument and position property. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/hover'
params: TextDocumentPositionParams

Response

result: Hover defined as follows:

/**
 * The result of a hover request.
 */
interface Hover {
	/**
	 * The hover's content
	 */
	contents: MarkedString | MarkedString[];
	
	/**
	 * An optional range is a range inside a text document 
	 * that is used to visualize a hover, e.g. by changing the background color.
	 */
	range?: Range;
}

Where MarkedString is defined as follows:

/**
 * The marked string is rendered:
 * - as markdown if it is represented as a string
 * - as code block of the given langauge if it is represented as a pair of a language and a value
 *
 * The pair of a language and a value is an equivalent to markdown:
 * ```${language}
 * ${value}
 * ```
 */
type MarkedString = string | { language: string; value: string };

error: code and message set in case an exception happens during the hover request.

Signature Help Request

The signature help request is sent from the client to the server to request signature information at a given cursor position.

Changed: In 2.0 the request uses TextDocumentPositionParams with proper textDocument and position properties. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/signatureHelp'
params: TextDocumentPositionParams

Response

result: SignatureHelp defined as follows:

/**
 * Signature help represents the signature of something
 * callable. There can be multiple signature but only one
 * active and only one active parameter.
 */
interface SignatureHelp {
	/**
	 * One or more signatures.
	 */
	signatures: SignatureInformation[];
	
	/**
	 * The active signature.
	 */
	activeSignature?: number;
	
	/**
	 * The active parameter of the active signature.
	 */
	activeParameter?: number;
}

/**
 * Represents the signature of something callable. A signature
 * can have a label, like a function-name, a doc-comment, and
 * a set of parameters.
 */
interface SignatureInformation {
	/**
	 * The label of this signature. Will be shown in
	 * the UI.
	 */
	label: string;
	
	/**
	 * The human-readable doc-comment of this signature. Will be shown
	 * in the UI but can be omitted.
	 */
	documentation?: string;
	
	/**
	 * The parameters of this signature.
	 */
	parameters?: ParameterInformation[];
}

/**
 * Represents a parameter of a callable-signature. A parameter can
 * have a label and a doc-comment.
 */
interface ParameterInformation {
	/**
	 * The label of this parameter. Will be shown in
	 * the UI.
	 */
	label: string;
	
	/**
	 * The human-readable doc-comment of this parameter. Will be shown
	 * in the UI but can be omitted.
	 */
	documentation?: string;
}

error: code and message set in case an exception happens during the signature help request.

Goto Definition Request

The goto definition request is sent from the client to the server to resolve the definition location of a symbol at a given text document position.

Changed: In 2.0 the request uses TextDocumentPositionParams with proper textDocument and position properties. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/definition'
params: TextDocumentPositionParams

Response:

result: Location | Location[]
error: code and message set in case an exception happens during the definition request.

Find References Request

The references request is sent from the client to the server to resolve project-wide references for the symbol denoted by the given text document position.

Changed: In 2.0 the request uses TextDocumentPositionParams with proper textDocument and position properties. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/references'
params: ReferenceParams defined as follows:

interface ReferenceParams extends TextDocumentPositionParams {
	context: ReferenceContext
}

interface ReferenceContext {
	/**
	 * Include the declaration of the current symbol.
	 */
	includeDeclaration: boolean;
}

Response:

result: Location[]
error: code and message set in case an exception happens during the reference request.

Document Highlights Request

The document highlight request is sent from the client to the server to resolve a document highlights for a given text document position. For programming languages this usually highlights all references to the symbol scoped to this file. However we kept 'textDocument/documentHighlight' and 'textDocument/references' separate requests since the first one is allowed to be more fuzzy. Symbol matches usually have a DocumentHighlightKind of Read or Write whereas fuzzy or textual matches use Textas the kind.

Changed: In 2.0 the request uses TextDocumentPositionParams with proper textDocument and position properties. In 1.0 the uri of the referenced text document was inlined into the params object.

Request

method: 'textDocument/documentHighlight'
params: TextDocumentPositionParams

Response

result: DocumentHighlight[] defined as follows:

/**
 * A document highlight is a range inside a text document which deserves
 * special attention. Usually a document highlight is visualized by changing
 * the background color of its range.
 * 
 */
interface DocumentHighlight {
	/**
	 * The range this highlight applies to.
	 */
	range: Range;

	/**
	 * The highlight kind, default is DocumentHighlightKind.Text.
	 */
	kind?: number;
}

/**
 * A document highlight kind.
 */
enum DocumentHighlightKind {
	/**
	 * A textual occurrance.
	 */
	Text = 1,

	/**
	 * Read-access of a symbol, like reading a variable.
	 */
	Read = 2,

	/**
	 * Write-access of a symbol, like writing to a variable.
	 */
	Write = 3
}

error: code and message set in case an exception happens during the document highlight request.

Document Symbols Request

The document symbol request is sent from the client to the server to list all symbols found in a given text document.

Changed: In 2.0 the request uses DocumentSymbolParams instead of a single uri.

Request

method: 'textDocument/documentSymbol'
params: DocumentSymbolParams defined as follows:

interface DocumentSymbolParams {
	/**
	 * The text document.
	 */
	textDocument: TextDocumentIdentifier;
}

Response

result: SymbolInformation[] defined as follows:

/**
 * Represents information about programming constructs like variables, classes,
 * interfaces etc.
 */
interface SymbolInformation {
	/**
	 * The name of this symbol.
	 */
	name: string;

	/**
	 * The kind of this symbol.
	 */
	kind: number;

	/**
	 * The location of this symbol.
	 */
	location: Location;

	/**
	 * The name of the symbol containing this symbol.
	 */
	containerName?: string;
}

Where the kind is defined like this:

/**
 * A symbol kind.
 */
export enum SymbolKind {
	File = 1,
	Module = 2,
	Namespace = 3,
	Package = 4,
	Class = 5,
	Method = 6,
	Property = 7,
	Field = 8,
	Constructor = 9,
	Enum = 10,
	Interface = 11,
	Function = 12,
	Variable = 13,
	Constant = 14,
	String = 15,
	Number = 16,
	Boolean = 17,
	Array = 18,
}

error: code and message set in case an exception happens during the document symbol request.

Workspace Symbols Request

The workspace symbol request is sent from the client to the server to list project-wide symbols matching the query string.

Request

method: 'workspace/symbol'
params: WorkspaceSymbolParams defined as follows:

/**
 * The parameters of a Workspace Symbol Request.
 */
interface WorkspaceSymbolParams {
	/**
	 * A non-empty query string
	 */
	query: string;
}

Response

result: SymbolInformation[] as defined above.
error: code and message set in case an exception happens during the workspace symbol request.

Code Action Request

The code action request is sent from the client to the server to compute commands for a given text document and range. The request is triggered when the user moves the cursor into a problem marker in the editor or presses the lightbulb associated with a marker.

Request

method: 'textDocument/codeAction'
params: CodeActionParams defined as follows:

/**
 * Params for the CodeActionRequest
 */
interface CodeActionParams {
	/**
	 * The document in which the command was invoked.
	 */
	textDocument: TextDocumentIdentifier;
	
	/**
	 * The range for which the command was invoked.
	 */
	range: Range;
	
	/**
	 * Context carrying additional information.
	 */
	context: CodeActionContext;
}

/**
 * Contains additional diagnostic information about the context in which
 * a code action is run.
 */
interface CodeActionContext {
	/**
	 * An array of diagnostics.
	 */
	diagnostics: Diagnostic[];
}

Response

result: Command[] defined as follows:
error: code and message set in case an exception happens during the code action request.

Code Lens Request

The code lens request is sent from the client to the server to compute code lenses for a given text document.

Changed: In 2.0 the request uses CodeLensParams instead of a single uri.

Request

method: 'textDocument/codeLens'
params: CodeLensParams defined as follows:

interface CodeLensParams {
	/**
	 * The document to request code lens for.
	 */
	textDocument: TextDocumentIdentifier;
}

Response

result: CodeLens[] defined as follows:

/**
 * A code lens represents a command that should be shown along with
 * source text, like the number of references, a way to run tests, etc.
 *
 * A code lens is _unresolved_ when no command is associated to it. For performance
 * reasons the creation of a code lens and resolving should be done in two stages.
 */
interface CodeLens {
	/**
	 * The range in which this code lens is valid. Should only span a single line.
	 */
	range: Range;

	/**
	 * The command this code lens represents.
	 */
	command?: Command;
	
	/**
	 * A data entry field that is preserved on a code lens item between
	 * a code lens and a code lens resolve request.
	 */
	data?: any
}

error: code and message set in case an exception happens during the code lens request.

Code Lens Resolve Request

The code lens resolve request is sent from the client to the server to resolve the command for a given code lens item.

Request

method: 'codeLens/resolve'
params: CodeLens

Response

result: CodeLens
error: code and message set in case an exception happens during the code lens resolve request.

Document Formatting Request

The document formatting request is sent from the server to the client to format a whole document.

Request

method: 'textDocument/formatting'
params: DocumentFormattingParams defined as follows

interface DocumentFormattingParams {
	/**
	 * The document to format.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * The format options.
	 */
	options: FormattingOptions;
}

/**
 * Value-object describing what options formatting should use.
 */
interface FormattingOptions {
	/**
	 * Size of a tab in spaces.
	 */
	tabSize: number;

	/**
	 * Prefer spaces over tabs.
	 */
	insertSpaces: boolean;

	/**
	 * Signature for further properties.
	 */
	[key: string]: boolean | number | string;
}

Response

result: TextEdit[] describing the modification to the document to be formatted.
error: code and message set in case an exception happens during the formatting request.

Document Range Formatting Request

The document range formatting request is sent from the client to the server to format a given range in a document.

Request

method: 'textDocument/rangeFormatting',
params: DocumentRangeFormattingParams defined as follows

interface DocumentRangeFormattingParams {
	/**
	 * The document to format.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * The range to format
	 */
	range: Range;

	/**
	 * The format options
	 */
	options: FormattingOptions;
}

Response

result: TextEdit[] describing the modification to the document to be formatted.
error: code and message set in case an exception happens during the range formatting request.

Document on Type Formatting Request

The document on type formatting request is sent from the client to the server to format parts of the document during typing.

Request

method: 'textDocument/onTypeFormatting'
params: DocumentOnTypeFormattingParams defined as follows

interface DocumentOnTypeFormattingParams {
	/**
	 * The document to format.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * The position at which this request was sent.
	 */
	position: Position;

	/**
	 * The character that has been typed.
	 */
	ch: string;
	
	/**
	 * The format options.
	 */
	options: FormattingOptions;
}

Response

result: TextEdit[] describing the modification to the document.
error: code and message set in case an exception happens during the range formatting request.

Rename Request

The rename request is sent from the client to the server to perform a workspace-wide rename of a symbol.

Request

method: 'textDocument/rename'
params: RenameParams defined as follows

interface RenameParams {
	/**
	 * The document to format.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * The position at which this request was sent.
	 */
	position: Position;

	/**
	 * The new name of the symbol. If the given name is not valid the
	 * request must return a [ResponseError](#ResponseError) with an
	 * appropriate message set.
	 */
	newName: string;
}

Response

result: WorkspaceEdit describing the modification to the workspace.
error: code and message set in case an exception happens during the rename request.

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Language Server Protocol

Base Protocol

Header Part

Content Part

Example:

Base Protocol JSON structures

Abstract Message

RequestMessage

Response Message

Notification Message

Cancellation Support

Language Server Protocol

Basic JSON Structures

Position

Range

Location

Diagnostic

Command

TextEdit

WorkspaceEdit

TextDocumentIdentifier

TextDocumentItem

VersionedTextDocumentIdentifier

TextDocumentPositionParams

Actual Protocol

Initialize Request

Shutdown Request

Exit Notification

ShowMessage Notification

ShowMessage Request

LogMessage Notification

Telemetry Notification

DidChangeConfiguration Notification

DidOpenTextDocument Notification

DidChangeTextDocument Notification

DidCloseTextDocument Notification

DidSaveTextDocument Notification

DidChangeWatchedFiles Notification

PublishDiagnostics Notification

Completion Request

Completion Item Resolve Request

Hover Request

Signature Help Request

Goto Definition Request

Find References Request

Document Highlights Request

Document Symbols Request

Workspace Symbols Request

Code Action Request

Code Lens Request

Code Lens Resolve Request

Document Formatting Request

Document Range Formatting Request

Document on Type Formatting Request

Rename Request