Fix "Select all" behavior in the editor (#33167)

* Make isEntirelySelected consider "deep" first and last children in case the selection does not belong to the top-level children directly

* Rollback unit tests – jsdom does not support contentEditable jsdom/jsdom#1670

* Add an e2e test for multi-block selection

* Adjust e2e tests

* Add a separate test for gradual select-all from within the list block

* Cosmetic adjustments to the e2e test

* Update the snapshot

packages/dom/src/dom/is-entirely-selected.js

@@ -48,15 +48,37 @@ export default function isEntirelySelected( element ) {
 
 	const lastChild = element.lastChild;
 	assertIsDefined( lastChild, 'lastChild' );
-	const lastChildContentLength =
-		lastChild.nodeType === lastChild.TEXT_NODE
-			? /** @type {Text} */ ( lastChild ).data.length
-			: lastChild.childNodes.length;
+	const endContainerContentLength =
+		endContainer.nodeType === endContainer.TEXT_NODE
+			? /** @type {Text} */ ( endContainer ).data.length
+			: endContainer.childNodes.length;
 
 	return (
-		startContainer === element.firstChild &&
-		endContainer === element.lastChild &&
+		isDeepChild( startContainer, element, 'firstChild' ) &&
+		isDeepChild( endContainer, element, 'lastChild' ) &&
 		startOffset === 0 &&
-		endOffset === lastChildContentLength
+		endOffset === endContainerContentLength
 	);
 }
+
+/**
+ * Check whether the contents of the element have been entirely selected.
+ * Returns true if there is no possibility of selection.
+ *
+ * @param {HTMLElement|Node} query The element to check.
+ * @param {HTMLElement} container The container that we suspect "query" may be a first or last child of.
+ * @param {"firstChild"|"lastChild"} propName "firstChild" or "lastChild"
+ *
+ * @return {boolean} True if query is a deep first/last child of container, false otherwise.
+ */
+function isDeepChild( query, container, propName ) {
+	/** @type {HTMLElement | ChildNode | null} */
+	let candidate = container;
+	do {
+		if ( query === candidate ) {
+			return true;
+		}
+		candidate = candidate[ propName ];
+	} while ( candidate );
+	return false;
+}

packages/e2e-tests/specs/editor/various/__snapshots__/multi-block-selection.test.js.snap

@@ -94,6 +94,16 @@ exports[`Multi-block selection should gradually multi-select 2`] = `
 <!-- /wp:columns -->"
 `;
 
+exports[`Multi-block selection should multi-select from within the list block 1`] = `
+"<!-- wp:paragraph -->
+<p>1</p>
+<!-- /wp:paragraph -->
+
+<!-- wp:list -->
+<ul><li>1</li></ul>
+<!-- /wp:list -->"
+`;
+
 exports[`Multi-block selection should not multi select single block 1`] = `
 "<!-- wp:paragraph -->
 <p></p>

packages/e2e-tests/specs/editor/various/multi-block-selection.test.js

@@ -655,4 +655,25 @@ describe( 'Multi-block selection', () => {
 		// Expect both columns to be deleted.
 		expect( await getEditedPostContent() ).toMatchSnapshot();
 	} );
+
+	it( 'should multi-select from within the list block', async () => {
+		await clickBlockAppender();
+		// Select a paragraph.
+		await page.keyboard.type( '1' );
+		await page.keyboard.press( 'Enter' );
+		// Add a list
+		await page.keyboard.type( '/list' );
+		await page.keyboard.press( 'Enter' );
+		await page.keyboard.type( '1' );
+
+		// Confirm correct setup: a paragraph and a list
+		expect( await getEditedPostContent() ).toMatchSnapshot();
+
+		await pressKeyWithModifier( 'primary', 'a' );
+		await pressKeyWithModifier( 'primary', 'a' );
+
+		await page.waitForSelector(
+			'[data-type="core/paragraph"].is-multi-selected'
+		);
+	} );
 } );