Fix terminal sticky scroll showing output instead of the executed command

src/vs/workbench/contrib/terminalContrib/stickyScroll/browser/terminalStickyScrollOverlay.ts

@@ -279,7 +279,6 @@ export class TerminalStickyScrollOverlay extends Disposable {
 		const buffer = xterm.buffer.active;
 		const promptRowCount = command.getPromptRowCount();
 		const commandRowCount = command.getCommandRowCount();
-		const stickyScrollLineStart = startMarker.line - (promptRowCount - 1);
 
 		// Calculate the row offset, this is the number of rows that will be clipped from the top
 		// of the sticky overlay because we do not want to show any content above the bounds of the
@@ -288,11 +287,11 @@ export class TerminalStickyScrollOverlay extends Disposable {
 		const isPartialCommand = !isFullTerminalCommand(command);
 		const rowOffset = !isPartialCommand && command.endMarker ? Math.max(buffer.viewportY - command.endMarker.line + 1, 0) : 0;
 		const maxLineCount = Math.min(this._rawMaxLineCount, Math.floor(xterm.rows * Constants.StickyScrollPercentageCap));
-		const stickyScrollLineCount = Math.min(promptRowCount + commandRowCount - 1, maxLineCount) - rowOffset;
-		const isTruncated = stickyScrollLineCount < promptRowCount + commandRowCount - 1;
+		const { lineStart: stickyScrollLineStart, lineCount: stickyScrollLineCount, isTruncated } = getStickyScrollLayout(startMarker.line, promptRowCount, commandRowCount, maxLineCount, rowOffset);
 
-		// Hide sticky scroll if it's currently on a line that contains it
-		if (buffer.viewportY <= stickyScrollLineStart) {
+		// Hide sticky scroll if there is nothing to show or if it's currently on a line that
+		// contains it
+		if (stickyScrollLineCount <= 0 || buffer.viewportY <= stickyScrollLineStart) {
 			this._setVisible(false);
 			return;
 		}
@@ -554,3 +553,39 @@ function lineStartsWith(line: IBufferLine | undefined, text: string): boolean {
 	}
 	return true;
 }
+
+/**
+ * Determines what part of a command's prompt and command line to show in the sticky scroll overlay.
+ *
+ * The command line is prioritized over the prompt, only including the prompt when the prompt and
+ * the command line both fit within `maxLineCount`. This matters because the rows above the command
+ * line are not necessarily prompt rows, for example output printed in between the previous command
+ * finishing and the prompt being drawn (job control notifications, background processes, etc.) is
+ * considered part of the prompt. Including those rows regardless would push the command line out of
+ * the overlay, showing only output and hiding the command the output belongs to.
+ *
+ * @param commandStartLine The buffer line the command line starts on.
+ * @param promptRowCount The number of rows the prompt spans, including the command start row.
+ * @param commandRowCount The number of rows the command line spans, including the command start row.
+ * @param maxLineCount The maximum number of rows the overlay is allowed to show.
+ * @param rowOffset The number of rows to clip from the top of the overlay. A `lineCount` of 0 means
+ * the row offset clipped all rows and there is nothing to show.
+ */
+export function getStickyScrollLayout(
+	commandStartLine: number,
+	promptRowCount: number,
+	commandRowCount: number,
+	maxLineCount: number,
+	rowOffset: number
+): { lineStart: number; lineCount: number; isTruncated: boolean } {
+	// The prompt and the command line share the command start row
+	const promptAndCommandRowCount = promptRowCount + commandRowCount - 1;
+	const includePrompt = promptAndCommandRowCount <= maxLineCount;
+	const contentRowCount = includePrompt ? promptAndCommandRowCount : commandRowCount;
+	const lineCount = Math.max(Math.min(contentRowCount, maxLineCount) - rowOffset, 0);
+	return {
+		lineStart: includePrompt ? commandStartLine - (promptRowCount - 1) : commandStartLine,
+		lineCount,
+		isTruncated: lineCount < contentRowCount
+	};
+}

src/vs/workbench/contrib/terminalContrib/stickyScroll/test/browser/terminalStickyScrollOverlay.test.ts

@@ -0,0 +1,84 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import type { Terminal } from '@xterm/xterm';
+import { deepStrictEqual } from 'assert';
+import { importAMDNodeModule } from '../../../../../../amdX.js';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../../base/test/common/utils.js';
+import { CommandDetectionCapability } from '../../../../../../platform/terminal/common/capabilities/commandDetectionCapability.js';
+import { TestXtermLogger } from '../../../../../../platform/terminal/test/common/terminalTestHelpers.js';
+import { workbenchInstantiationService } from '../../../../../test/browser/workbenchTestServices.js';
+import { writeP } from '../../../../terminal/browser/terminalTestHelpers.js';
+import { getStickyScrollLayout } from '../../browser/terminalStickyScrollOverlay.js';
+
+suite('TerminalStickyScrollOverlay', () => {
+	const store = ensureNoDisposablesAreLeakedInTestSuite();
+
+	suite('getStickyScrollLayout', () => {
+		test('should show the prompt and the command line when they fit', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 2, 1, 5, 0), { lineStart: 9, lineCount: 2, isTruncated: false });
+		});
+
+		test('should truncate the command line when it does not fit', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 1, 8, 5, 0), { lineStart: 10, lineCount: 5, isTruncated: true });
+		});
+
+		test('should drop the prompt when the prompt and the command line do not fit', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 6, 1, 5, 0), { lineStart: 10, lineCount: 1, isTruncated: false });
+		});
+
+		test('should prefer the command line rows over the prompt rows', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 2, 5, 5, 0), { lineStart: 10, lineCount: 5, isTruncated: false });
+		});
+
+		test('should clip rows from the top of the overlay for the row offset', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 3, 1, 5, 1), { lineStart: 8, lineCount: 2, isTruncated: true });
+		});
+
+		test('should show nothing when the row offset clips all rows', () => {
+			deepStrictEqual(getStickyScrollLayout(10, 6, 1, 5, 1), { lineStart: 10, lineCount: 0, isTruncated: true });
+		});
+	});
+
+	suite('command detection', () => {
+		let xterm: Terminal;
+		let capability: CommandDetectionCapability;
+
+		setup(async () => {
+			const TerminalCtor = (await importAMDNodeModule<typeof import('@xterm/xterm')>('@xterm/xterm', 'lib/xterm.js')).Terminal;
+			xterm = store.add(new TerminalCtor({ allowProposedApi: true, cols: 80, rows: 30, logger: TestXtermLogger }));
+			const instantiationService = workbenchInstantiationService(undefined, store);
+			capability = store.add(instantiationService.createInstance(CommandDetectionCapability, xterm));
+		});
+
+		test('should show the command line when output is printed after the previous command finished', async () => {
+			// A command finishes and more output is printed before the prompt is drawn. The prompt
+			// start is reported at the previous command's end, so that output is treated as part
+			// of the prompt of the following command.
+			capability.handlePromptStart();
+			await writeP(xterm, '\r$ ');
+			capability.handleCommandStart();
+			await writeP(xterm, 'npm install');
+			capability.handleCommandExecuted();
+			await writeP(xterm, '\r\nadded 100 packages\r\n');
+			capability.handleCommandFinished(0);
+			await writeP(xterm, 'output printed after the command finished\r\n'.repeat(5));
+
+			capability.handlePromptStart();
+			await writeP(xterm, '$ ');
+			capability.handleCommandStart();
+			await writeP(xterm, './scripts/code.sh');
+			capability.handleCommandExecuted();
+
+			const command = capability.currentCommand!;
+			const commandStartLine = command.commandStartMarker!.line;
+			const promptRowCount = command.getPromptRowCount();
+			deepStrictEqual(
+				{ promptRowCount, ...getStickyScrollLayout(commandStartLine, promptRowCount, command.getCommandRowCount(), 5, 0) },
+				{ promptRowCount: 6, lineStart: commandStartLine, lineCount: 1, isTruncated: false }
+			);
+		});
+	});
+});