Lazily attach the linedataeventaddon

Fixes microsoft#166031

Author: Tyriar

src/vs/workbench/contrib/terminal/browser/terminalInstance.ts

@@ -210,6 +210,7 @@ export class TerminalInstance extends Disposable implements ITerminalInstance {
 	private _usedShellIntegrationInjection: boolean = false;
 	get usedShellIntegrationInjection(): boolean { return this._usedShellIntegrationInjection; }
 	private _quickFixAddon: TerminalQuickFixAddon | undefined;
+	private _lineDataEventAddon: LineDataEventAddon | undefined;
 
 	readonly capabilities = new TerminalCapabilityStoreMultiplexer();
 	readonly statusList: ITerminalStatusList;
@@ -337,7 +338,9 @@ export class TerminalInstance extends Disposable implements ITerminalInstance {
 	readonly onData = this._onData.event;
 	private readonly _onBinary = this._register(new Emitter<string>());
 	readonly onBinary = this._onBinary.event;
-	private readonly _onLineData = this._register(new Emitter<string>());
+	private readonly _onLineData = this._register(new Emitter<string>({
+		onDidAddFirstListener: () => this._onLineDataSetup()
+	}));
 	readonly onLineData = this._onLineData.event;
 	private readonly _onRequestExtHostProcess = this._register(new Emitter<ITerminalInstance>());
 	readonly onRequestExtHostProcess = this._onRequestExtHostProcess.event;
@@ -734,8 +737,6 @@ export class TerminalInstance extends Disposable implements ITerminalInstance {
 		this.xterm?.raw.loadAddon(this._quickFixAddon);
 		this.registerQuickFixProvider(gitTwoDashes(), freePort(this), gitSimilar(), gitPushSetUpstream(), gitCreatePr());
 		this._register(this._quickFixAddon.onDidRequestRerunCommand(async (e) => await this.runCommand(e.command, e.addNewLine || false)));
-		const lineDataEventAddon = new LineDataEventAddon();
-		this.xterm.raw.loadAddon(lineDataEventAddon);
 		this.updateAccessibilitySupport();
 		this.xterm.onDidRequestRunCommand(e => {
 			if (e.copyAsHtml) {
@@ -746,13 +747,10 @@ export class TerminalInstance extends Disposable implements ITerminalInstance {
 		});
 		// Write initial text, deferring onLineFeed listener when applicable to avoid firing
 		// onLineData events containing initialText
-		if (this._shellLaunchConfig.initialText) {
-			this._writeInitialText(this.xterm, () => {
-				lineDataEventAddon.onLineData(e => this._onLineData.fire(e));
-			});
-		} else {
-			lineDataEventAddon.onLineData(e => this._onLineData.fire(e));
-		}
+		const initialTextWrittenPromise = this._shellLaunchConfig.initialText ? new Promise<void>(r => this._writeInitialText(xterm, r)) : undefined;
+		const lineDataEventAddon = new LineDataEventAddon(initialTextWrittenPromise);
+		lineDataEventAddon.onLineData(e => this._onLineData.fire(e));
+		this._lineDataEventAddon = lineDataEventAddon;
 		// Delay the creation of the bell listener to avoid showing the bell when the terminal
 		// starts up or reconnects
 		setTimeout(() => {
@@ -822,6 +820,11 @@ export class TerminalInstance extends Disposable implements ITerminalInstance {
 		return xterm;
 	}
 
+	private async _onLineDataSetup(): Promise<void> {
+		const xterm = this.xterm || await this._xtermReadyPromise;
+		xterm.raw.loadAddon(this._lineDataEventAddon!);
+	}
+
 	async runCommand(commandLine: string, addNewLine: boolean): Promise<void> {
 		// Determine whether to send ETX (ctrl+c) before running the command. This should always
 		// happen unless command detection can reliably say that a command is being entered and

src/vs/workbench/contrib/terminal/browser/xterm/lineDataEventAddon.ts

@@ -19,8 +19,16 @@ export class LineDataEventAddon extends Disposable implements ITerminalAddon {
 	private readonly _onLineData = this._register(new Emitter<string>());
 	readonly onLineData = this._onLineData.event;
 
-	activate(xterm: XTermTerminal) {
+	constructor(private readonly _initializationPromise?: Promise<void>) {
+		super();
+	}
+
+	async activate(xterm: XTermTerminal) {
 		this._xterm = xterm;
+
+		// If there is an initialization promise, wait for it before registering the event
+		await this._initializationPromise;
+
 		// Fire onLineData when a line feed occurs, taking into account wrapped lines
 		this._register(xterm.onLineFeed(() => {
 			const buffer = xterm.buffer;