Fix broken editor when passing attributes as undefined or null and add warning for block authors

packages/blocks/src/api/test/registration.js

@@ -304,6 +304,56 @@ describe( 'blocks', () => {
 			} );
 		} );
 
+		it( 'should default to empty object when attributes is omitted and without warning', () => {
+			registerBlockType( 'core/test-block-omitted-attributes', {
+				title: 'block title',
+				category: 'text',
+				save: noop,
+			} );
+
+			// Verify no warning was shown (unlike when explicitly set to null/undefined)
+			expect( console ).not.toHaveWarned();
+
+			const blockType = getBlockType(
+				'core/test-block-omitted-attributes'
+			);
+			expect( blockType.attributes ).toEqual( {} );
+		} );
+
+		it( 'should warn and default to empty object when attributes is undefined', () => {
+			registerBlockType( 'core/test-block-undefined-attributes', {
+				title: 'block title',
+				category: 'text',
+				save: noop,
+				attributes: undefined,
+			} );
+
+			expect( console ).toHaveWarnedWith(
+				'The block "core/test-block-undefined-attributes" must not register attributes as `null` or `undefined`. Use an empty object (`attributes: {}`) or exclude the `attributes` key. In the next Gutenberg release, passing `null` or `undefined` for `attributes` will cause the block editor to crash.'
+			);
+
+			const blockType = getBlockType(
+				'core/test-block-undefined-attributes'
+			);
+			expect( blockType.attributes ).toEqual( {} );
+		} );
+
+		it( 'should warn and default to empty object when attributes is null', () => {
+			registerBlockType( 'core/test-block-null-attributes', {
+				title: 'block title',
+				category: 'text',
+				save: noop,
+				attributes: null,
+			} );
+
+			expect( console ).toHaveWarnedWith(
+				'The block "core/test-block-null-attributes" must not register attributes as `null` or `undefined`. Use an empty object (`attributes: {}`) or exclude the `attributes` key. In the next Gutenberg release, passing `null` or `undefined` for `attributes` will cause the block editor to crash.'
+			);
+
+			const blockType = getBlockType( 'core/test-block-null-attributes' );
+			expect( blockType.attributes ).toEqual( {} );
+		} );
+
 		it( 'should default to browser-initialized global attributes', () => {
 			const attributes = { ok: { type: 'boolean' } };
 			unstable__bootstrapServerSideBlockDefinitions( {

packages/blocks/src/store/process-block-type.js

@@ -103,6 +103,19 @@ export const processBlockType =
 			),
 		};
 
+		// Temporary fix to allow block authors time to fix blocks that register attributes as null or undefined.
+		if (
+			! blockType.attributes ||
+			typeof blockType.attributes !== 'object'
+		) {
+			warning(
+				'The block "' +
+					name +
+					'" must not register attributes as `null` or `undefined`. Use an empty object (`attributes: {}`) or exclude the `attributes` key. In the next Gutenberg release, passing `null` or `undefined` for `attributes` will cause the block editor to crash.'
+			);
+			blockType.attributes = {};
+		}
+
 		const settings = applyFilters(
 			'blocks.registerBlockType',
 			blockType,