public start()

in client/src/common/client.ts [3324:3438]
112 lines of code
22 McCabe index (conditional complexity)

	public start(): Disposable {
		if (this._onReadyCallbacks.isUsed) {
			this._onReady = new Promise((resolve, reject) => {
				this._onReadyCallbacks = new OnReady(resolve, reject);
			});
		}
		this._listeners = [];
		this._providers = [];
		// If we restart then the diagnostics collection is reused.
		if (!this._diagnostics) {
			this._diagnostics = this._clientOptions.diagnosticCollectionName
				? Languages.createDiagnosticCollection(this._clientOptions.diagnosticCollectionName)
				: Languages.createDiagnosticCollection();
		}

		this.state = ClientState.Starting;
		this.resolveConnection().then((connection) => {
			connection.onLogMessage((message) => {
				switch (message.type) {
					case MessageType.Error:
						this.error(message.message, undefined, false);
						break;
					case MessageType.Warning:
						this.warn(message.message, undefined, false);
						break;
					case MessageType.Info:
						this.info(message.message, undefined, false);
						break;
					default:
						this.outputChannel.appendLine(message.message);
				}
			});
			connection.onShowMessage((message) => {
				switch (message.type) {
					case MessageType.Error:
						void Window.showErrorMessage(message.message);
						break;
					case MessageType.Warning:
						void Window.showWarningMessage(message.message);
						break;
					case MessageType.Info:
						void Window.showInformationMessage(message.message);
						break;
					default:
						void Window.showInformationMessage(message.message);
				}
			});
			connection.onRequest(ShowMessageRequest.type, (params) => {
				let messageFunc: <T extends MessageItem>(message: string, ...items: T[]) => Thenable<T>;
				switch (params.type) {
					case MessageType.Error:
						messageFunc = Window.showErrorMessage;
						break;
					case MessageType.Warning:
						messageFunc = Window.showWarningMessage;
						break;
					case MessageType.Info:
						messageFunc = Window.showInformationMessage;
						break;
					default:
						messageFunc = Window.showInformationMessage;
				}
				let actions = params.actions || [];
				return messageFunc(params.message, ...actions);
			});
			connection.onTelemetry((data) => {
				this._telemetryEmitter.fire(data);
			});
			connection.onRequest(ShowDocumentRequest.type, async (params): Promise<ShowDocumentResult> => {
				const showDocument = async (params: ShowDocumentParams): Promise<ShowDocumentResult> => {
					const uri = this.protocol2CodeConverter.asUri(params.uri);
					try {
						if (params.external === true) {
							const success = await Env.openExternal(uri);
							return { success };
						} else {
							const options: TextDocumentShowOptions = {};
							if (params.selection !== undefined) {
								options.selection = this.protocol2CodeConverter.asRange(params.selection);
							}
							if (params.takeFocus === undefined || params.takeFocus === false) {
								options.preserveFocus = true;
							} else if (params.takeFocus === true) {
								options.preserveFocus = false;
							}
							await Window.showTextDocument(uri, options);
							return { success: true };
						}
					} catch (error) {
						return { success: true };
					}
				};
				const middleware = this._clientOptions.middleware.window?.showDocument;
				if (middleware !== undefined)  {
					return middleware(params, showDocument);
				} else {
					return showDocument(params);
				}
			});
			connection.listen();
			// Error is handled in the initialize call.
			return this.initialize(connection);
		}).catch((error) => {
			this.state = ClientState.StartFailed;
			this._onReadyCallbacks.reject(error);
			this.error(`${this._name} client: couldn't create connection to server`, error, 'force');
		});
		return new Disposable(() => {
			if (this.needsStop()) {
				this.stop().catch((error) => {
					this.error(`Stopping server failed.`, error, false);
				});
			}
		});
	}