Fix sibling block inserter displaying at end of block list. (#29920)

* Only show inserter version of insertion point if there is a next block

* Clarify comment

* Improve boolean logic

* Update e2e test

* Update tests

packages/block-editor/src/components/block-list/insertion-point.js

@@ -199,6 +199,18 @@ function InsertionPointPopover( {
 		}
 	}
 
+	// Only show the inserter when there's a `nextElement` (a block after the
+	// insertion point). At the end of the block list the trailing appender
+	// should serve the purpose of inserting blocks.
+	const showInsertionPointInserter =
+		! isHidden && nextElement && ( isInserterShown || isInserterForced );
+
+	// Show the indicator if the insertion point inserter is visible, or if
+	// the `showInsertionPoint` state is `true`. The latter is generally true
+	// when hovering blocks for insertion in the block library.
+	const showInsertionPointIndicator =
+		showInsertionPointInserter || ( ! isHidden && showInsertionPoint );
+
 	/* eslint-disable jsx-a11y/no-static-element-interactions, jsx-a11y/click-events-have-key-events */
 	// While ideally it would be enough to capture the
 	// bubbling focus event from the Inserter, due to the
@@ -223,13 +235,10 @@ function InsertionPointPopover( {
 				className={ className }
 				style={ style }
 			>
-				{ ! isHidden &&
-					( showInsertionPoint ||
-						isInserterShown ||
-						isInserterForced ) && (
-						<div className="block-editor-block-list__insertion-point-indicator" />
-					) }
-				{ ! isHidden && ( isInserterShown || isInserterForced ) && (
+				{ showInsertionPointIndicator && (
+					<div className="block-editor-block-list__insertion-point-indicator" />
+				) }
+				{ showInsertionPointInserter && (
 					<InsertionPointInserter
 						rootClientId={ rootClientId }
 						clientId={ nextClientId }

packages/e2e-tests/specs/experiments/multi-entity-saving.test.js

@@ -7,7 +7,6 @@ import {
 	publishPost,
 	trashAllPosts,
 	activateTheme,
-	canvas,
 } from '@wordpress/e2e-test-utils';
 
 /**
@@ -193,9 +192,13 @@ describe( 'Multi-entity save flow', () => {
 			await navigationPanel.clickItemByText( 'Index' );
 			await navigationPanel.close();
 
-			// Click the first block so that the template part inserts in the right place.
-			const firstBlock = await canvas().$( '.wp-block' );
-			await firstBlock.click();
+			// Select the header template part via list view.
+			await page.click( 'button[aria-label="List View"]' );
+			const headerTemplatePartListViewButton = await page.waitForXPath(
+				'//button[contains(@class, "block-editor-block-navigation-block-select-button")][contains(., "Header")]'
+			);
+			headerTemplatePartListViewButton.click();
+			await page.click( 'button[aria-label="Close list view sidebar"]' );
 
 			// Insert something to dirty the editor.
 			await insertBlock( 'Paragraph' );