fix: Console history did not stick to bottom on visibility changes

jest.setup.ts

@@ -50,6 +50,12 @@ Object.defineProperty(window, 'ResizeObserver', {
   },
 });
 
+Object.defineProperty(window, 'IntersectionObserver', {
+  value: function () {
+    return TestUtils.createMockProxy<IntersectionObserver>();
+  },
+});
+
 Object.defineProperty(window, 'DOMRect', {
   value: function (x: number = 0, y: number = 0, width = 0, height = 0) {
     return TestUtils.createMockProxy<DOMRect>({

packages/console/src/Console.tsx

@@ -7,6 +7,7 @@ import React, {
   type ReactElement,
   type ReactNode,
   type RefObject,
+  type UIEvent,
 } from 'react';
 import {
   ContextActions,
@@ -190,6 +191,7 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     this.handleLogMessage = this.handleLogMessage.bind(this);
     this.handleOverflowActions = this.handleOverflowActions.bind(this);
     this.handleScrollPaneScroll = this.handleScrollPaneScroll.bind(this);
+    this.handleVisibilityChange = this.handleVisibilityChange.bind(this);
     this.handleToggleAutoLaunchPanels =
       this.handleToggleAutoLaunchPanels.bind(this);
     this.handleToggleClosePanelsOnDisconnect =
@@ -213,6 +215,9 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     this.consoleHistoryScrollPane = React.createRef();
     this.pending = new Pending();
     this.queuedLogMessages = [];
+    this.visibilityObserver = new window.IntersectionObserver(
+      this.handleVisibilityChange
+    );
 
     const { objectMap, settings } = this.props;
 
@@ -253,6 +258,10 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     );
 
     this.updateDimensions();
+
+    if (this.consolePane.current) {
+      this.visibilityObserver.observe(this.consolePane.current);
+    }
   }
 
   componentDidUpdate(prevProps: ConsoleProps, prevState: ConsoleState): void {
@@ -280,6 +289,7 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     this.processLogMessageQueue.cancel();
 
     this.deinitConsoleLogging();
+    this.visibilityObserver.disconnect();
   }
 
   cancelListener?: () => void;
@@ -294,6 +304,8 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
 
   queuedLogMessages: ConsoleHistoryActionItem[];
 
+  visibilityObserver: IntersectionObserver;
+
   initConsoleLogging(): void {
     const { session } = this.props;
     this.cancelListener = session.onLogMessage(this.handleLogMessage);
@@ -670,7 +682,8 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     });
   }
 
-  handleScrollPaneScroll(): void {
+  handleScrollPaneScroll(event: UIEvent<HTMLDivElement>): void {
+    log.debug('handleScrollPaneScroll', event);
     const scrollPane = this.consoleHistoryScrollPane.current;
     assertNotNull(scrollPane);
     this.setState({
@@ -681,6 +694,18 @@ export class Console extends PureComponent<ConsoleProps, ConsoleState> {
     });
   }
 
+  handleVisibilityChange(entries: IntersectionObserverEntry[]): void {
+    log.debug('handleVisibilityChange', entries);
+
+    const entry = entries[0];
+    if (entry.isIntersecting) {
+      const { isStuckToBottom } = this.state;
+      if (isStuckToBottom && !this.isAtBottom()) {
+        this.scrollConsoleHistoryToBottom();
+      }
+    }
+  }
+
   handleToggleAutoLaunchPanels(): void {
     this.setState(state => ({
       isAutoLaunchPanelsEnabled: !state.isAutoLaunchPanelsEnabled,

tests/console.spec.ts

@@ -6,6 +6,20 @@ import {
   generateId,
 } from './utils';
 
+function logMessageLocator(page: Page, text: string): Locator {
+  return page
+    .locator('.console-history .log-message')
+    .filter({ hasText: text });
+}
+
+function panelTabLocator(page: Page, text: string): Locator {
+  return page.locator('.lm_tab .lm_title').filter({ hasText: text });
+}
+
+function scrollPanelLocator(page: Page): Locator {
+  return page.locator('.console-pane .scroll-pane');
+}
+
 let page: Page;
 let consoleInput: Locator;
 
@@ -32,9 +46,8 @@ test.describe('console input tests', () => {
     await page.keyboard.press('Enter');
 
     // Expect the output to show up in the log
-    await expect(
-      page.locator('.console-history .log-message').filter({ hasText: message })
-    ).toHaveCount(1);
+    await expect(logMessageLocator(page, message)).toHaveCount(1);
+    await expect(logMessageLocator(page, message)).toBeVisible();
   });
 
   test('object button is created when creating a table', async ({
@@ -61,3 +74,53 @@ test.describe('console input tests', () => {
     await expect(btnLocator.nth(1)).not.toBeDisabled();
   });
 });
+
+test.describe('console scroll tests', () => {
+  test('scrolls to the bottom when command is executed', async () => {
+    // The command needs to be long, but it doesn't need to actually print anything
+    const ids = Array.from(Array(300).keys()).map(() => generateId());
+    const command = ids.map(i => `# Really long command ${i}`).join('\n');
+
+    await pasteInMonaco(consoleInput, command);
+    await page.keyboard.press('Enter');
+
+    // Allow time for the text to colorize/render
+    await page.waitForTimeout(100);
+
+    // Expect the console to be scrolled to the bottom
+    const scrollPane = await scrollPanelLocator(page);
+    expect(
+      await scrollPane.evaluate(el => {
+        return el.scrollHeight - el.scrollTop - el.clientHeight;
+      })
+    ).toBeLessThanOrEqual(0);
+  });
+
+  test('scrolls to the bottom when focus changed when command executed', async () => {
+    // The command needs to be long, but it doesn't need to actually print anything
+    const ids = Array.from(Array(300).keys()).map(() => generateId());
+    const command =
+      `import time\ntime.sleep(0.5)\n` +
+      ids.map(i => `# Really long command ${i}`).join('\n');
+
+    await pasteInMonaco(consoleInput, command);
+    await page.keyboard.press('Enter');
+
+    // Immediately open the log before the command code block has a chance to finish colorizing/rendering
+    await panelTabLocator(page, 'Log').click();
+
+    // wait for a bit for the code block to render
+    // Since it's in the background, we can't use the waitForSelector method. It should render in less than 1s.
+    await page.waitForTimeout(1000);
+
+    // Switch back to the console, and expect it to be scrolled to the bottom
+    await panelTabLocator(page, 'Console').click();
+
+    const scrollPane = await scrollPanelLocator(page);
+    expect(
+      await scrollPane.evaluate(el => {
+        return el.scrollHeight - el.scrollTop - el.clientHeight;
+      })
+    ).toBeLessThanOrEqual(0);
+  });
+});