Writing Flow: Test horizontal navigation as handled

Specifically for TinyMCE's overrides on inline boundary traversal

editor/components/writing-flow/index.js

@@ -53,6 +53,41 @@ const isTabbableTextField = overEvery( [
 	focus.tabbable.isTabbableIndex,
 ] );
 
+/**
+ * Returns true if the given node is a TinyMCE inline boundary node.
+ *
+ * @param {Node} node Node to test.
+ *
+ * @return {boolean} Whether node is a TinyMCE inline boundary node.
+ */
+function isInlineBoundary( node ) {
+	return node.getAttribute( 'data-mce-selected' ) === 'inline-boundary';
+}
+
+/**
+ * Returns true if it can be inferred that horizontal navigation has already
+ * been handled in the desired direction, or false otherwise. Specifically,
+ * this accounts for TinyMCE's inline boundary traversal, where its keydown
+ * event takes effect before the event propagates to WritingFlow. This avoids
+ * the caret from being moved outside the block when inline boundary occurs at
+ * the end of a RichText.
+ *
+ * @see tinymce/src/core/main/ts/keyboard/ArrowKeys.ts (executeKeydownOverride)
+ *
+ * @param {boolean} isReverse Whether to test in reverse.
+ *
+ * @return {boolean} Whether horizontal navigation has been handled.
+ */
+function isHorizontalNavigationHandled( isReverse ) {
+	const { isCollapsed, focusNode } = getSelection();
+	if ( ! isCollapsed ) {
+		return false;
+	}
+
+	const siblingNode = focusNode[ isReverse ? 'nextSibling' : 'previousSibling' ];
+	return !! siblingNode && isInlineBoundary( siblingNode );
+}
+
 class WritingFlow extends Component {
 	constructor() {
 		super( ...arguments );
@@ -217,7 +252,8 @@ class WritingFlow extends Component {
 				placeCaretAtVerticalEdge( closestTabbable, isReverse, this.verticalRect );
 				event.preventDefault();
 			}
-		} else if ( isHorizontal && getSelection().isCollapsed && isHorizontalEdge( target, isReverse ) ) {
+		} else if ( isHorizontal && getSelection().isCollapsed &&
+				! isHorizontalNavigationHandled( isReverse ) && isHorizontalEdge( target, isReverse ) ) {
 			const closestTabbable = this.getClosestTabbable( target, isReverse );
 			placeCaretAtHorizontalEdge( closestTabbable, isReverse );
 			event.preventDefault();

test/e2e/specs/__snapshots__/writing-flow.test.js.snap

@@ -13,3 +13,25 @@ exports[`adding blocks Should navigate with arrow keys 5`] = `"The Greeting: <br
 exports[`adding blocks Should navigate with arrow keys 6`] = `"Prefix: Hello"`;
 
 exports[`adding blocks Should navigate with arrow keys 7`] = `"The Greeting: <br>Hello to the World! (Suffix)"`;
+
+exports[`adding blocks Should navigate with arrow keys 8`] = `"<span id=\\"_mce_caret\\" data-mce-bogus=\\"1\\"><strong data-mce-selected=\\"inline-boundary\\">Bolded</strong></span><br data-mce-bogus=\\"1\\">"`;
+
+exports[`adding blocks Should navigate with arrow keys 9`] = `"<strong data-mce-selected=\\"inline-boundary\\">Bolded Words</strong><br data-mce-bogus=\\"1\\">"`;
+
+exports[`adding blocks Should navigate with arrow keys 10`] = `"<strong>Bolded Words</strong>After<br data-mce-bogus=\\"1\\">"`;
+
+exports[`adding blocks Should navigate with arrow keys 11`] = `"The Greeting: <br>Hello to the World! (Suffixed)"`;
+
+exports[`adding blocks Should navigate with arrow keys 12`] = `
+"<!-- wp:paragraph -->
+<p>The Greeting: <br/>Hello to the World! (Suffixed)</p>
+<!-- /wp:paragraph -->
+
+<!-- wp:paragraph -->
+<p><strong>Bolded Words</strong>After</p>
+<!-- /wp:paragraph -->
+
+<!-- wp:paragraph -->
+<p>Prefix: Hello</p>
+<!-- /wp:paragraph -->"
+`;

test/e2e/specs/writing-flow.test.js

@@ -7,7 +7,12 @@ import { times } from 'lodash';
  * Internal dependencies
  */
 import '../support/bootstrap';
-import { newPost, newDesktopBrowserPage, pressWithModifier } from '../support/utils';
+import {
+	newPost,
+	newDesktopBrowserPage,
+	pressWithModifier,
+	getHTMLFromCodeEditor,
+} from '../support/utils';
 
 describe( 'adding blocks', () => {
 	beforeAll( async () => {
@@ -111,5 +116,36 @@ describe( 'adding blocks', () => {
 		await page.keyboard.up( 'Shift' );
 		await page.keyboard.type( ' (Suffix)' );
 		await expectParagraphToMatchSnapshot( 1 );
+
+		// Should arrow once to escape out of inline boundary (bold, etc), and
+		// escaping out should nullify any block traversal.
+		await page.keyboard.press( 'Enter' );
+		await pressWithModifier( 'Mod', 'B' ); // Bold
+		await page.keyboard.type( 'Bolded' );
+		await expectParagraphToMatchSnapshot( 2 );
+
+		// Pressing space while having escaped on right edge of inline boundary
+		// should continue text as bolded.
+		await page.keyboard.press( 'ArrowRight' );
+		await page.keyboard.type( ' Words' );
+		await expectParagraphToMatchSnapshot( 2 );
+
+		// But typing immediately after escaping should not be within.
+		await page.keyboard.press( 'ArrowRight' );
+		await page.keyboard.type( 'After' );
+		await expectParagraphToMatchSnapshot( 2 );
+
+		// Navigate back to previous block. Change "(Suffix)" to "(Suffixed)"
+		//
+		// "Bolded WordsAfter" =   17 characters
+		//                       +  2 inline boundaries
+		//                       +  1 horizontal block traversal
+		//                       +  1 into parenthesis
+		//                       = 21
+		await promiseSequence( times( 21, () => () => page.keyboard.press( 'ArrowLeft' ) ) );
+		await page.keyboard.type( 'ed' );
+		await expectParagraphToMatchSnapshot( 1 );
+
+		expect( await getHTMLFromCodeEditor() ).toMatchSnapshot();
 	} );
 } );