Introduce strip_dynamic_blocks() for excerpts

lib/blocks.php

@@ -88,6 +88,30 @@ function get_dynamic_block_names() {
 	return $dynamic_block_names;
 }
 
+/**
+ * Retrieve the dynamic blocks regular expression for searching.
+ *
+ * @return string
+ */
+function get_dynamic_blocks_regex() {
+	$dynamic_block_names   = get_dynamic_block_names();
+	$dynamic_block_pattern = (
+		'/<!--\s+wp:(' .
+		str_replace( '/', '\/',                 // Escape namespace, not handled by preg_quote.
+			str_replace( 'core/', '(?:core/)?', // Allow implicit core namespace, but don't capture.
+				implode( '|',                   // Join block names into capture group alternation.
+					array_map( 'preg_quote',    // Escape block name for regular expression.
+						$dynamic_block_names
+					)
+				)
+			)
+		) .
+		')(\s+(\{.*?\}))?\s+(\/)?-->/'
+	);
+
+	return $dynamic_block_pattern;
+}
+
 /**
  * Renders a single block into a HTML string.
  *
@@ -124,22 +148,8 @@ function gutenberg_render_block( $block ) {
  * @return string          Updated post content.
  */
 function do_blocks( $content ) {
-	$rendered_content = '';
-
-	$dynamic_block_names   = get_dynamic_block_names();
-	$dynamic_block_pattern = (
-		'/<!--\s+wp:(' .
-		str_replace( '/', '\/',                 // Escape namespace, not handled by preg_quote.
-			str_replace( 'core/', '(?:core/)?', // Allow implicit core namespace, but don't capture.
-				implode( '|',                   // Join block names into capture group alternation.
-					array_map( 'preg_quote',    // Escape block name for regular expression.
-						$dynamic_block_names
-					)
-				)
-			)
-		) .
-		')(\s+(\{.*?\}))?\s+(\/)?-->/'
-	);
+	$rendered_content      = '';
+	$dynamic_block_pattern = get_dynamic_blocks_regex();
 
 	while ( preg_match( $dynamic_block_pattern, $content, $block_match, PREG_OFFSET_CAPTURE ) ) {
 		$opening_tag     = $block_match[0][0];
@@ -208,3 +218,46 @@ function do_blocks( $content ) {
 	return $rendered_content;
 }
 add_filter( 'the_content', 'do_blocks', 9 ); // BEFORE do_shortcode().
+
+/**
+ * Remove all dynamic blocks from the given content.
+ *
+ * @param string $content Content of the current post.
+ * @return string
+ */
+function strip_dynamic_blocks( $content ) {
+	return preg_replace( get_dynamic_blocks_regex(), '', $content );
+}
+
+/**
+ * Adds the content filter to strip dynamic blocks from excerpts.
+ *
+ * It's a bit hacky for now, but once this gets merged into core the function
+ * can just be called in `wp_trim_excerpt()`.
+ *
+ * @param string $text Excerpt.
+ *
+ * @return string
+ */
+function strip_dynamic_blocks_add_filter( $text ) {
+	add_filter( 'the_content', 'strip_dynamic_blocks', 8 ); // Before do_blocks().
+
+	return $text;
+}
+add_filter( 'get_the_excerpt', 'strip_dynamic_blocks_add_filter', 9 ); // Before wp_trim_excerpt().
+
+/**
+ * Adds the content filter to strip dynamic blocks from excerpts.
+ *
+ * It's a bit hacky for now, but once this gets merged into core the function
+ * can just be called in `wp_trim_excerpt()`.
+ *
+ * @param string $text Excerpt.
+ * @return string
+ */
+function strip_dynamic_blocks_remove_filter( $text ) {
+	remove_filter( 'the_content', 'strip_dynamic_blocks', 8 );
+
+	return $text;
+}
+add_filter( 'wp_trim_excerpt', 'strip_dynamic_blocks_add_filter', 0 ); // Before all other.

phpunit/class-blocks-api-test.php

@@ -0,0 +1,111 @@
+<?php
+/**
+ * Blocks API Tests
+ *
+ * @package Gutenberg
+ */
+
+/**
+ * Test functions in blocks.php
+ */
+class Blocks_API extends WP_UnitTestCase {
+
+	public static $post_id;
+
+	public $content = '
+<!-- wp:paragraph -->
+<p>paragraph</p>
+<!-- /wp:paragraph -->
+
+<!-- wp:latest-posts {"postsToShow":3,"displayPostDate":true,"order":"asc","orderBy":"title"} /-->
+
+<!-- wp:spacer -->
+<div style="height:100px" aria-hidden="true" class="wp-block-spacer"></div>
+<!-- /wp:spacer -->';
+
+	public $filtered_content = '
+<!-- wp:paragraph -->
+<p>paragraph</p>
+<!-- /wp:paragraph -->
+
+
+
+<!-- wp:spacer -->
+<div style="height:100px" aria-hidden="true" class="wp-block-spacer"></div>
+<!-- /wp:spacer -->';
+
+	/**
+	 * Dummy block rendering function.
+	 *
+	 * @return string Block output.
+	 */
+	function render_dummy_block() {
+		return get_the_excerpt( self::$post_id );
+	}
+
+	/**
+	 * Set up.
+	 */
+	function setUp() {
+		parent::setUp();
+
+		self::$post_id = $this->factory()->post->create( array(
+			'post_excerpt' => '', // Empty excerpt, so it has to be generated.
+			'post_content' => '<!-- wp:core/dummy /-->',
+		) );
+
+		register_block_type( 'core/dummy', array(
+			'render_callback' => array( $this, 'render_dummy_block' ),
+		) );
+	}
+
+	/**
+	 * Tear down.
+	 */
+	function tearDown() {
+		parent::tearDown();
+
+		$registry = WP_Block_Type_Registry::get_instance();
+		$registry->unregister( 'core/dummy' );
+
+		wp_delete_post( self::$post_id, true );
+	}
+
+	/**
+	 * Tests strip_dynamic_blocks().
+	 *
+	 * @covers ::strip_dynamic_blocks
+	 */
+	function test_strip_dynamic_blocks() {
+		// Simple dynamic block..
+		$content = '<!-- wp:core/block /-->';
+		$this->assertEmpty( strip_dynamic_blocks( $content ) );
+
+		// Dynamic block with options, embedded in other content.
+		$this->assertEquals( $this->filtered_content, strip_dynamic_blocks( $this->content ) );
+	}
+
+	/**
+	 * Tests that dynamic blocks don't cause an out-of-memory error.
+	 *
+	 * When dynamic blocks happen to generate an excerpt, they can cause an
+	 * infinite loop if that block is part of the post's content.
+	 *
+	 * `wp_trim_excerpt()` applies the `the_content` filter, which has
+	 * `do_blocks` attached to it, trying to render the block which again will
+	 * attempt to return an excerpt of that post.
+	 *
+	 * This infinite loop can be avoided by stripping dynamic blocks before
+	 * `the_content` gets applied, just like shortcodes.
+	 *
+	 * @covers ::strip_dynamic_blocks_add_filter, ::strip_dynamic_blocks_remove_filter
+	 */
+	function test_excerpt_infinite_loop() {
+		$query = new WP_Query( array(
+			'post__in' => array( self::$post_id ),
+		) );
+		$query->the_post();
+
+		$this->assertEmpty( do_blocks( '<!-- wp:core/dummy /-->' ) );
+	}
+}