Language Server Protocol

Language Server Protocol (LSP) support is available in the Dart analysis server from version 2.2.0 of the SDK (which was included in version 1.2.1 of Flutter). The supported messages are detailed below (for the version of the SDK that matches this README).

Using the Dart LSP server in editors

• Using LSP with Dart-Vim
• Using LSP with Emacs

Running the Server

Start the language server using the dart language-server command. Pass the --client-id and --client-version flags to identify your editor/plugin and version:

dart language-server --client-id my-editor.my-plugin --client-version 1.2

Note: In LSP the client makes the first request so there is no obvious confirmation that the server is working correctly until the client sends an initialize request. Unlike standard JSON RPC, LSP requires that headers are sent.

Handling of “Loose” Files

When there are no open workspace folders (or if the initialization option onlyAnalyzeProjectsWithOpenFiles is set to true), analysis will be performed based on project folders located by the open files. For each open file, the project root will be located, and that whole project analyzed. If the file does not have a project (eg. there is no pubspec.yaml in its ancestor folders) then the file will be analyzed in isolation.

Initialization Options

• onlyAnalyzeProjectsWithOpenFiles (bool?): When set to true, workspace folders will be ignored and analysis will be performed based on the open files, as if no workspace was open at all. This allows opening large folders without causing them to be completely analyzed. Defaults to false.
• suggestFromUnimportedLibraries (bool?): When set to false, completion will not include symbols that are not already imported into the current file. Defaults to true, though the client must additionally support workspace/applyEdit for these completions to be included.
• closingLabels (bool?): When set to true, dart/textDocument/publishClosingLabels notifications will be sent with information to render editor closing labels.
• outline (bool?): When set to true, dart/textDocument/publishOutline notifications will be sent with outline information for open files.
• flutterOutline (bool?): When set to true, dart/textDocument/publishFlutterOutline notifications will be sent with Flutter outline information for open files.
• allowOpenUri: When set to true, indicates that the client will handle dart/openUri notifications by opening a browser for the supplied URI.

Client Workspace Configuration

Client workspace settings are requested with workspace/configuration during initialization and re-requested whenever the client notifies the server with workspace/didChangeConfiguration. This allows the settings to take effect without restarting the server.

• dart.analysisExcludedFolders (List<String>?): An array of paths (absolute or relative to each workspace folder) that should be excluded from analysis.
• dart.enableSdkFormatter (bool?): When set to false, prevents registration (or unregisters) the SDK formatter. When set to true or not supplied, will register/reregister the SDK formatter.
• dart.lineLength (int?): The number of characters the formatter should wrap code at. If unspecified, code will be wrapped at 80 characters.
• dart.completeFunctionCalls (bool?): When set to true, completes functions/methods with their required parameters.
• dart.showTodos (bool?): Whether to generate diagnostics for TODO comments. If unspecified, diagnostics will not be generated.
• dart.renameFilesWithClasses (String): When set to "always", will include edits to rename files when classes are renamed if the filename matches the class name (but in snake_form). When set to "prompt", a prompt will be shown on each class rename asking to confirm the file rename. Otherwise, files will not be renamed. Renames are performed using LSP's ResourceOperation edits - that means the rename is simply included in the resulting WorkspaceEdit and must be handled by the client.
• dart.enableSnippets (bool?): Whether to include code snippets (such as class, stful, switch) in code completion. When unspecified, snippets will be included.
• dart.updateImportsOnRename (bool?): Whether to update imports and other directives when files are renamed. When unspecified, imports will be updated if the client supports willRenameFiles requests.
• dart.documentation (none, summary or full): The typekind of dartdocs to include in Hovers, Code Completion, Signature Help and other similar requests. If not set, defaults to full.
• dart.includeDependenciesInWorkspaceSymbols (bool?): Whether to include symbols from dependencies and Dart/Flutter SDKs in Workspace Symbol results. If not set, defaults to true.

Method Status

Below is a list of LSP methods and their implementation status.

• Method: The LSP method name
• Basic Impl: This method has an implementation but may assume some client capabilities
• Capabilities: Only types from the original spec or as advertised in client capabilities are returned
• Plugins: This functionality works with server plugins
• Tests: Has automated tests
• Tested Client: Has been manually tested in at least one LSP client editor

Method	Server	Plugins	Notes
initialize	✅	N/A	trace and other options NYI
initialized	✅	N/A
shutdown	✅	N/A	supported but does nothing
exit	✅	N/A
$/cancelRequest	✅
$/logTrace
$/progress
$/setTrace
client/registerCapability	✅	✅
client/unregisterCapability	✅	✅
notebookDocument/*
telemetry/event
textDocument/codeAction (assists)	✅	✅	Only if the client advertises codeActionLiteralSupport with Refactor
textDocument/codeAction (fixAll)	✅
textDocument/codeAction (fixes)	✅	✅	Only if the client advertises codeActionLiteralSupport with QuickFix
textDocument/codeAction (organiseImports)	✅
textDocument/codeAction (refactors)	✅
textDocument/codeAction (sortMembers)	✅
codeAction/resolve
textDocument/codeLens	✅
codeLens/resolve
textDocument/completion	✅	✅
completionItem/resolve	✅
textDocument/declaration
textDocument/definition	✅	✅
textDocument/diagnostic
textDocument/didChange	✅	✅
textDocument/didClose	✅	✅
textDocument/didOpen	✅	✅
textDocument/didSave
textDocument/documentColor	✅
textDocument/colorPresentation	✅
textDocument/documentHighlight	✅
textDocument/documentLink	✅
documentLink/resolve
textDocument/documentSymbol	✅
textDocument/foldingRange	✅	✅
textDocument/formatting	✅
textDocument/onTypeFormatting	✅
textDocument/rangeFormatting	✅
textDocument/hover	✅
textDocument/implementation	✅
textDocument/inlayHint	✅
inlayHint/resolve
textDocument/inlineValue
textDocument/linkedEditingRange
textDocument/moniker
textDocument/prepareCallHierarchy	✅
callHierarchy/incomingCalls	✅
callHierarchy/outgoingCalls	✅
textDocument/prepareRename	✅
textDocument/rename	✅
textDocument/prepareTypeHierarchy	✅
typeHierarchy/subtypes	✅
typeHierarchy/supertypes	✅
textDocument/publishDiagnostics	✅	✅
textDocument/references	✅
textDocument/selectionRange	✅
textDocument/semanticTokens/full	✅	✅
textDocument/semanticTokens/full/delta
textDocument/semanticTokens/range	✅	✅
workspace/semanticTokens/refresh
textDocument/signatureHelp	✅
textDocument/typeDefinition	✅
textDocument/willSave
textDocument/willSaveWaitUntil
window/logMessage	✅
window/showDocument
window/showMessage	✅
window/showMessageRequest
window/workDoneProgress/cancel
window/workDoneProgress/create	✅
workspace/applyEdit	✅
workspace/codeLens/refresh
workspace/configuration	✅
workspace/diagnostic
workspace/diagnostic/refresh
workspace/didChangeConfiguration	✅
workspace/didChangeWatchedFiles			unused, server does own watching
workspace/didChangeWorkspaceFolders	✅	✅
workspace/didCreateFiles
workspace/didDeleteFiles
workspace/didRenameFiles
workspace/executeCommand	✅
workspace/inlayHint/refresh
workspace/inlineValue/refresh
workspace/symbol	✅
workspaceSymbol/resolve
workspace/willCreateFiles
workspace/willDeleteFiles
workspace/willRenameFiles
workspace/willRenameFiles	✅
workspace/workspaceFolders

Custom Fields, Methods and Notifications

The following custom fields/methods/notifications are also provided by the Dart LSP server:

Message.clientRequestTime Field

The server accepts an optional int? on all incoming messages named clientRequestTime (alongside id, method, params) containing a timestamp (milliseconds since epoch) of when the client made that request. Providing clientRequestTime helps track how responsive analysis server is to client requests and better address any issues that occur.

dart/diagnosticServer Method

Direction: Client -> Server Params: None Returns: { port: number }

Starts the analyzer diagnostics server (if not already running) and returns the port number it's listening on.

dart/reanalyze Method

Direction: Client -> Server Params: None Returns: None

Forces re-reading of all potentially changed files, re-resolving of all referenced URIs, and corresponding re-analysis of everything affected in the current analysis roots. Clients should not usually need to call this method - needing to do so may indicate a bug in the server.

dart/textDocument/super Method

Direction: Client -> Server Params: TextDocumentPositionParams Returns: Location | null

Returns the location of the super definition of the class or method at the provided position or null if there isn't one.

dart/textDocument/augmented Method

Direction: Client -> Server Params: TextDocumentPositionParams Returns: Location | null

Returns the location of the declaration that is augmented at the provided position or null if the position is not an augmentation.

dart/textDocument/augmentation Method

Direction: Client -> Server Params: TextDocumentPositionParams Returns: Location | null

Returns the location of the augmentation for the declaration at the provided position or null if declaration is not augmented.

$/analyzerStatus Notification (Deprecated)

Direction: Server -> Client Params: { isAnalyzing: boolean }

Notifies the client when analysis starts/completes.

This notification is not sent if the client capabilities include window.workDoneProgress == true because analyzing status events will be sent using $/progress.

This notification may be removed in a future Dart SDK release and should not be depended on.

dart/textDocument/publishClosingLabels Notification

Direction: Server -> Client Params: { uri: string, labels: { label: string, range: Range }[] }

Notifies the client when closing label information is available (or updated) for a file.

dart/textDocument/publishOutline Notification

Direction: Server -> Client Params: { uri: string, outline: Outline } Outline: { element: Element, range: Range, codeRange: Range, children: Outline[] } Element: { name: string, range: Range, kind: string, parameters: string | undefined, typeParameters: string | undefined, returnType: string | undefined }

Notifies the client when outline information is available (or updated) for a file.

Nodes contains multiple ranges:

• element.range - the range of the name in the declaration of the element
• range - the entire range of the declaration including dartdocs
• codeRange - the range of code part of the declaration (excluding dartdocs and annotations) - typically used when navigating to the declaration

dart/textDocument/publishFlutterOutline Notification

Direction: Server -> Client Params: { uri: string, outline: FlutterOutline } FlutterOutline: { dartElement: Element | undefined, range: Range, codeRange: Range, children: Outline[], kind: string, label: string | undefined, className: string | undefined, variableName: string | undefined, attributes: FlutterOutlineAttribute[] | undefined } FlutterOutlineAttribute: { name: string, label: string } Element: as defined for the dart/textDocument/publishOutline notification.

Notifies the client when Flutter outline information is available (or updated) for a file.

Nodes contains multiple ranges as described for the dart/textDocument/publishOutline notification.

dart/openUri Notification

Direction: Server -> Client Params: { uri: Uri }

Notifies the client that the server would like to open a given URI. This event is only sent in response to direct user actions (such as if the user clicks a “Learn More” button in a window/showMessageRequest). URIs could be either external web pages (http/https) to be opened in the browser or documents (file:///) to be opened in the editor.

This notification (and functionality that relies on it) will only be sent if the client passes allowOpenUri: true in initializationOptions.

dart/textDocumentContent Method (Experimental)

Direction: Client -> Server Params: { uri: Uri } Returns: { content: string | undefined }

Returns the content of the the virtual document with uri. This is intended for generated files (such as those generated by macros) and is not supported for ‘file’ URIs.

dart/textDocumentContentDidChange Notification

Direction: Server -> Client Params: { uri: Uri }

Notifies the client that the content in the virtual file with uri may have changed (for example because a macro executed and regenerated its content).

Client Commands

Some server functionality relies on well-known commands being available on the client. For example some CodeLenses like “Go to Augmented” required that the server can tell the client to navigate to a specific Location. To enable this functionality, the client must inform the server which commands it supports from the set below during initialization in the experimental.commands field of the client capabilities.

{
	// ... other client capabilities
	"experimental": {
		"commands": [
			"dart.goToLocation",
		]
	}
}

dart.goToLocation Client Command

Arguments: Location

This command takes a single Location argument and should navigate to that location in the editor. The server may use this command in CodeLenses or other places where a Command can be returned. For example:

// Response to textDocument/codeLens
[
	// CodeLens
	{
		"range": {
			"end": { "character": 0, "line": 2 },
			"start": { "character": 0, "line": 2 }
		},
		// Command
		"command": {
			"title": "Go to Augmented",
			"command": "dart.goToLocation",
			"arguments": [
				// Location
				{
					"uri": "file:///C:/Projects/my_app/lib/main.dart",
					"range": {
						"end": { "character": 7, "line": 2 },
						"start": { "character": 6, "line": 2 }
					}
				}
			]
		}
	}
]