From 9f04d785bc2055897d186e9287dfc9f6458c3819 Mon Sep 17 00:00:00 2001
From: Andrew Duthie <andrew@andrewduthie.com>
Date: Thu, 23 May 2019 07:40:27 -0400
Subject: [PATCH] Block Editor: Avoid default block insertion if no default
 block type (#15786)

* Block Editor: Select previous / next only when exists

* Block Editor: Avoid default block insertion if no default block type

* Testing: Verify graceful behavior of no-default block deletion
---
 packages/block-editor/src/store/actions.js    |  8 ++++-
 .../e2e-tests/specs/block-deletion.test.js    | 31 +++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/packages/block-editor/src/store/actions.js b/packages/block-editor/src/store/actions.js
index 876083194ef8b7..4dafaa291fcf31 100644
--- a/packages/block-editor/src/store/actions.js
+++ b/packages/block-editor/src/store/actions.js
@@ -637,7 +637,13 @@ export function selectionChange( clientId, attributeKey, startOffset, endOffset
  * @return {Object} Action object
  */
 export function insertDefaultBlock( attributes, rootClientId, index ) {
-	const block = createBlock( getDefaultBlockName(), attributes );
+	// Abort if there is no default block type (if it has been unregistered).
+	const defaultBlockName = getDefaultBlockName();
+	if ( ! defaultBlockName ) {
+		return;
+	}
+
+	const block = createBlock( defaultBlockName, attributes );
 
 	return insertBlock( block, index, rootClientId );
 }
diff --git a/packages/e2e-tests/specs/block-deletion.test.js b/packages/e2e-tests/specs/block-deletion.test.js
index fb975fb61e88ce..6adcb01681bb2a 100644
--- a/packages/e2e-tests/specs/block-deletion.test.js
+++ b/packages/e2e-tests/specs/block-deletion.test.js
@@ -7,6 +7,7 @@ import {
 	createNewPost,
 	isInDefaultBlock,
 	pressKeyWithModifier,
+	insertBlock,
 } from '@wordpress/e2e-test-utils';
 
 const addThreeParagraphsToNewPost = async () => {
@@ -130,4 +131,34 @@ describe( 'deleting all blocks', () => {
 		// And focus is retained:
 		expect( await isInDefaultBlock() ).toBe( true );
 	} );
+
+	it( 'gracefully removes blocks when the default block is not available', async () => {
+		// Regression Test: Previously, removing a block would not clear
+		// selection state when there were no other blocks to select.
+		//
+		// See: https://github.com/WordPress/gutenberg/issues/15458
+		// See: https://github.com/WordPress/gutenberg/pull/15543
+		await createNewPost();
+
+		// Unregister default block type. This may happen if the editor is
+		// configured to not allow the default (paragraph) block type, either
+		// by plugin editor settings filtering or user block preferences.
+		await page.evaluate( () => {
+			const defaultBlockName = wp.data.select( 'core/blocks' ).getDefaultBlockName();
+			wp.data.dispatch( 'core/blocks' ).removeBlockTypes( defaultBlockName );
+		} );
+
+		// Add and remove a block.
+		await insertBlock( 'Image' );
+		await page.keyboard.press( 'Backspace' );
+
+		// Verify there is no selected block.
+		// TODO: There should be expectations around where focus is placed in
+		// this scenario. Currently, a focus loss occurs (not acceptable).
+		const selectedBlocksCount = await page.evaluate( () => {
+			return wp.data.select( 'core/block-editor' ).getSelectedBlockClientIds().length;
+		} );
+
+		expect( selectedBlocksCount ).toBe( 0 );
+	} );
 } );