PromptInputModel: Don't fire change event on no change

Author: Tyriar

src/vs/platform/terminal/common/capabilities/commandDetection/promptInputModel.ts

@@ -141,19 +141,16 @@ export class PromptInputModel extends Disposable implements IPromptInputModel {
 			return;
 		}
 
-		// Command start line
-		this._value = commandLine;
-
-		// Get cursor index
 		const absoluteCursorY = buffer.baseY + buffer.cursorY;
-		this._cursorIndex = absoluteCursorY === commandStartY ? this._getRelativeCursorIndex(this._commandStartX, buffer, line) : commandLine.length + 1;
-		this._ghostTextIndex = -1;
+		let value = commandLine;
+		let cursorIndex = absoluteCursorY === commandStartY ? this._getRelativeCursorIndex(this._commandStartX, buffer, line) : commandLine.length + 1;
+		let ghostTextIndex = -1;
 
 		// Detect ghost text by looking for italic or dim text in or after the cursor and
 		// non-italic/dim text in the cell closest non-whitespace cell before the cursor
 		if (absoluteCursorY === commandStartY && buffer.cursorX > 1) {
 			// Ghost text in pwsh only appears to happen on the cursor line
-			this._ghostTextIndex = this._scanForGhostText(buffer, line);
+			ghostTextIndex = this._scanForGhostText(buffer, line);
 		}
 
 		// IDEA: Detect line continuation if it's not set
@@ -167,8 +164,8 @@ export class PromptInputModel extends Disposable implements IPromptInputModel {
 				// user likely just pressed enter
 				if (this._continuationPrompt === undefined || this._lineContainsContinuationPrompt(lineText)) {
 					lineText = this._trimContinuationPrompt(lineText);
-					this._value += `\n${lineText}`;
-					this._cursorIndex += (absoluteCursorY === y
+					value += `\n${lineText}`;
+					cursorIndex += (absoluteCursorY === y
 						? this._getRelativeCursorIndex(this._getContinuationPromptCellWidth(line, lineText), buffer, line)
 						: lineText.length + 1);
 				} else {
@@ -183,7 +180,7 @@ export class PromptInputModel extends Disposable implements IPromptInputModel {
 			const lineText = line?.translateToString(true);
 			if (lineText && line) {
 				if (this._continuationPrompt === undefined || this._lineContainsContinuationPrompt(lineText)) {
-					this._value += `\n${this._trimContinuationPrompt(lineText)}`;
+					value += `\n${this._trimContinuationPrompt(lineText)}`;
 				} else {
 					break;
 				}
@@ -194,7 +191,12 @@ export class PromptInputModel extends Disposable implements IPromptInputModel {
 			this._logService.trace(`PromptInputModel#_sync: ${this.getCombinedString()}`);
 		}
 
-		this._onDidChangeInput.fire();
+		if (this._value !== value || this._cursorIndex !== cursorIndex || this._ghostTextIndex !== ghostTextIndex) {
+			this._value = value;
+			this._cursorIndex = cursorIndex;
+			this._ghostTextIndex = ghostTextIndex;
+			this._onDidChangeInput.fire();
+		}
 	}
 
 	/**

src/vs/platform/terminal/test/common/capabilities/commandDetection/promptInputModel.test.ts

@@ -11,7 +11,7 @@ import type { ITerminalCommand } from 'vs/platform/terminal/common/capabilities/
 
 // eslint-disable-next-line local/code-import-patterns, local/code-amd-node-module
 import { Terminal } from '@xterm/headless';
-import { strictEqual } from 'assert';
+import { notDeepStrictEqual, strictEqual } from 'assert';
 import { timeout } from 'vs/base/common/async';
 
 suite('PromptInputModel', () => {
@@ -78,6 +78,46 @@ suite('PromptInputModel', () => {
 		await assertPromptInput('|');
 	});
 
+	test('should not fire events when nothing changes', async () => {
+		const events: {
+			value: string;
+			cursorIndex: number;
+			ghostTextIndex: number;
+		}[] = [];
+		store.add(promptInputModel.onDidChangeInput(() => {
+			events.push({
+				value: promptInputModel.value,
+				cursorIndex: promptInputModel.cursorIndex,
+				ghostTextIndex: promptInputModel.ghostTextIndex
+			});
+		}));
+
+		await writePromise('$ ');
+		fireCommandStart();
+		await assertPromptInput('|');
+
+		await writePromise('foo');
+		await assertPromptInput('foo|');
+
+		await writePromise(' bar');
+		await assertPromptInput('foo bar|');
+
+		await writePromise('\r\n');
+		fireCommandExecuted();
+		await assertPromptInput('foo bar');
+
+		await writePromise('$ ');
+		fireCommandStart();
+		await assertPromptInput('|');
+
+		await writePromise('foo bar');
+		await assertPromptInput('foo bar|');
+
+		for (let i = 0; i < events.length - 1; i++) {
+			notDeepStrictEqual(events[i], events[i + 1], 'not adjacent events should fire with the same value');
+		}
+	});
+
 	test('cursor navigation', async () => {
 		await writePromise('$ ');
 		fireCommandStart();