fix: enforce display condition to return string in render_block filter

inc/plugins/class-block-conditions.php

@@ -26,7 +26,7 @@ class Block_Conditions {
 	 */
 	public function init() {
 		if ( get_option( 'themeisle_blocks_settings_block_conditions', true ) ) {
-			add_action( 'render_block', array( $this, 'render_blocks' ), 999, 2 );
+			add_filter( 'render_block', array( $this, 'render_blocks' ), 999, 2 );
 			add_action( 'wp_loaded', array( $this, 'add_attributes_to_blocks' ), 999 );
 		}
 	}
@@ -36,6 +36,8 @@ public function init() {
 	 *
 	 * @param string $block_content Content of block.
 	 * @param array  $block Block Attributes.
+	 * 
+	 * @return string
 	 *
 	 * @since   1.7.0
 	 * @access  public
@@ -46,12 +48,12 @@ public function render_blocks( $block_content, $block ) {
 			$display = $this->evaluate_condition_collection( $block['attrs']['otterConditions'] );
 
 			if ( false === $display ) {
-				return;
+				return '';
 			}
 
 			$enhanced_content = $this->should_add_hide_css_class( $this->get_hide_css_condition( $block['attrs']['otterConditions'] ), $block_content );
 
-			if ( false !== $enhanced_content ) {
+			if ( false !== $enhanced_content && is_string( $enhanced_content ) ) {
 				return $enhanced_content;
 			}
 		}

src/blocks/test/e2e/blocks/block-conditions.spec.js

@@ -0,0 +1,49 @@
+/**
+ * WordPress dependencies
+ */
+import { test, expect } from '@wordpress/e2e-test-utils-playwright';
+import { tryLoginIn } from '../utils';
+
+test.describe( 'Block Conditions', () => {
+	test.beforeEach( async({ admin, requestUtils, page }) => {
+		await tryLoginIn( page, 'admin', 'password' );
+		await admin.createNewPost();
+	});
+
+	test.afterEach( async({ page }) => {
+
+		/**
+		 * Because some conditions require an user to be logged in, we need to log in the user after each test so that we do not break the next test.
+		 */
+		await tryLoginIn( page, 'admin', 'password' );
+	});
+
+	test( 'check logged out users', async({ editor, page, admin, requestUtils }) => {
+		await editor.insertBlock({
+			name: 'core/image',
+			attributes: {
+				url: 'https://mllj2j8xvfl0.i.optimole.com/cb:jC7e.37109/w:794/h:397/q:mauto/dpr:2.0/f:best/https://themeisle.com/blog/wp-content/uploads/2021/01/How-to-Change-Font-in-WordPress-Theme.png',
+				otterConditions: [
+					[
+						{
+							type: 'loggedInUser'
+						}
+					]
+				]
+			}
+		});
+
+		const postId = await editor.publishPost();
+
+		// Check the block for logged in users.
+		await page.goto( `/?p=${postId}` );
+		await expect( page.locator( '#wp--skip-link--target img' ) ).toBeVisible();
+
+		// Check the block for logged out users.
+		await page.getByRole( 'menuitem', { name: 'Howdy, admin' }).hover();
+		await page.waitForTimeout( 200 );
+		await page.getByRole( 'menuitem', { name: 'Log Out' }).click();
+		await page.goto( `/?p=${postId}` );
+		await expect( page.locator( '#wp--skip-link--target img' ) ).toBeHidden();
+	});
+});

src/blocks/test/e2e/utils.js

@@ -68,3 +68,10 @@ export function deleteFile( filePath ) {
 		unlinkSync( filePath );
 	}
 }
+
+export async function tryLoginIn( page, username, password ) {
+	await page.goto( '/wp-login.php' );
+	await page.fill( 'input[name="log"]', username );
+	await page.fill( 'input[name="pwd"]', password );
+	await page.click( 'input[name="wp-submit"]' );
+}