Prevent extra lines from sticking to terminal after cycling through multi line commands in history

Author: robertoffmoura

src/commandwindow/CommandWindow.ts

@@ -566,7 +566,9 @@ export default class CommandWindow implements vscode.Pseudoterminal {
     }
 
     private _eraseExistingPromptLine (): void {
-        const numberOfLinesBehind = Math.floor(this._getAbsoluteIndexOnLine(this._cursorIndex) / this._terminalDimensions.columns);
+        const textUpToCursor = this._currentPromptLine.substring(0, this._getAbsoluteIndexOnLine(this._cursorIndex));
+        const numberOfExplicitNewlines = (textUpToCursor.match(/\r?\n/g) ?? []).length;
+        const numberOfLinesBehind = Math.floor(this._getAbsoluteIndexOnLine(this._cursorIndex) / this._terminalDimensions.columns) + numberOfExplicitNewlines;
         if (numberOfLinesBehind !== 0) {
             this._writeEmitter.fire(ACTION_KEYS.UP.repeat(numberOfLinesBehind))
         }

src/test/tools/tester/TerminalTester.ts

@@ -48,6 +48,13 @@ export class TerminalTester {
         return await this.vs.poll(this.doesTerminalContain.bind(this, expected), true, `Assertion on terminal content: ${message}`)
     }
 
+    /**
+     * Assert the MATLAB terminal does not contain some content
+     */
+    public async assertNotContains (expected: string, message: string): Promise<void> {
+        return await this.vs.poll(this.doesTerminalNotContain.bind(this, expected), true, `Assertion on terminal content: ${message}`)
+    }
+
     /**
      * Checks if the MATLAB terminal contains some content (no polling)
      */
@@ -56,6 +63,14 @@ export class TerminalTester {
         return content.includes(expected)
     }
 
+    /**
+     * Checks if the MATLAB terminal does not contain some content (no polling)
+     */
+    private async doesTerminalNotContain (expected: string): Promise<boolean> {
+        const content = await this.getTerminalContent()
+        return !content.includes(expected)
+    }
+
     public async type (text: string): Promise<void> {
         const container = await this.terminal.findElement(vet.By.className('xterm-helper-textarea'));
         return await container.sendKeys(text)

src/test/ui/terminal.test.ts

@@ -90,4 +90,26 @@ suite('Terminal UI Tests', () => {
         await vs.terminal.assertContains('a = 123;', 'Up arrow after typing "a" should recall matching command')
         await vs.terminal.type(Key.ESCAPE)
     });
+
+    test('Test multi-line command history cycling', async () => {
+        // Execute a multi-line command by pasting (simulates copy-paste of multi-line text)
+        await vs.terminal.type('x = [1 2\n     3 4]')
+        await vs.terminal.type(Key.RETURN)
+
+        // Execute another command to move forward in history
+        await vs.terminal.executeCommand('y = 5;')
+        await vs.terminal.executeCommand('clc')
+
+        // Recall the multi-line command with up arrow
+        await vs.terminal.type(Key.ARROW_UP)
+        await vs.terminal.type(Key.ARROW_UP)
+        await vs.terminal.assertContains('x = [1 2', 'Up arrow should recall first line of multi-line command')
+        await vs.terminal.assertContains('3 4]', 'Up arrow should recall second line of multi-line command')
+
+        // Cycle away from the multi-line command
+        await vs.terminal.type(Key.ARROW_DOWN)
+        await vs.terminal.assertNotContains('x = [1 2', 'First line should not stick after cycling away with down arrow')
+        await vs.terminal.assertNotContains('3 4]', 'Second line should not stick after cycling away with down arrow')
+        await vs.terminal.type(Key.ESCAPE)
+    });
 });