Query: Improved handling of filtered queries in WP_Query.

The `WP_Query` class enables developers to customize queries using filters like `posts_fields_request`, `posts_request`, and `the_posts`, which can modify both the queried fields and retrieved post objects. In some cases with these filters, incomplete or invalid post objects lacking essential data may arise. To address this, if any of these filters are active during a query, the `get_posts` method now avoids caching post objects with the usual `update_post_caches` function call, opting for a call to `_prime_post_caches` instead. This may occasionally trigger new database queries to prime the post data cache. While this enhancement may result in rare additional database queries, it ensures that invalid post objects aren't cached, prioritizing data consistency and integrity in filtered query scenarios.

Props saulirajala, spacedmonkey, flixos90, mukesh27, peterwilsoncc.
Fixes #58599.

git-svn-id: https://develop.svn.wordpress.org/trunk@56656 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-query.php

@@ -3270,10 +3270,11 @@ public function get_posts() {
 			return $post_parents;
 		}
 
+		$is_unfiltered_query = $old_request == $this->request && "{$wpdb->posts}.*" === $fields;
+
 		if ( null === $this->posts ) {
 			$split_the_query = (
-				$old_request == $this->request
-				&& "{$wpdb->posts}.*" === $fields
+				$is_unfiltered_query
 				&& (
 					wp_using_ext_object_cache()
 					|| ( ! empty( $limits ) && $q['posts_per_page'] < 500 )
@@ -3337,6 +3338,8 @@ public function get_posts() {
 			$this->posts = array_map( 'get_post', $this->posts );
 		}
 
+		$unfiltered_posts = $this->posts;
+
 		if ( $q['cache_results'] && $id_query_is_cacheable && ! $cache_found ) {
 			$post_ids = wp_list_pluck( $this->posts, 'ID' );
 
@@ -3529,7 +3532,12 @@ public function get_posts() {
 			$this->posts = array_map( 'get_post', $this->posts );
 
 			if ( $q['cache_results'] ) {
-				update_post_caches( $this->posts, $post_type, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
+				if ( $is_unfiltered_query && $unfiltered_posts === $this->posts ) {
+					update_post_caches( $this->posts, $post_type, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
+				} else {
+					$post_ids = wp_list_pluck( $this->posts, 'ID' );
+					_prime_post_caches( $post_ids, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
+				}
 			}
 
 			/** @var WP_Post */

tests/phpunit/tests/query/cacheResults.php

@@ -1079,6 +1079,85 @@ public function test_query_cache_delete_term() {
 		$this->assertNotSame( $query1->found_posts, $query2->found_posts );
 	}
 
+	/**
+	 * @ticket 58599
+	 */
+	public function test_query_posts_fields_request() {
+		global $wpdb;
+
+		$args = array(
+			'update_post_meta_cache' => false,
+			'update_post_term_cache' => false,
+			'no_found_rows'          => true,
+		);
+
+		add_filter( 'posts_fields_request', array( $this, 'filter_posts_fields_request' ) );
+
+		$before = get_num_queries();
+		$query1 = new WP_Query();
+		$posts1 = $query1->query( $args );
+		$after  = get_num_queries();
+
+		foreach ( $posts1 as $_post ) {
+			$this->assertNotSame( get_post( $_post->ID )->post_content, $_post->post_content );
+		}
+
+		$this->assertSame( 2, $after - $before, 'There should only be 2 queries run, one for request and one prime post objects.' );
+
+		$this->assertStringContainsString(
+			"SELECT $wpdb->posts.*",
+			$wpdb->last_query,
+			'Check that _prime_post_caches is called.'
+		);
+	}
+
+	public function filter_posts_fields_request( $fields ) {
+		global $wpdb;
+		return "{$wpdb->posts}.ID";
+	}
+
+	/**
+	 * @ticket 58599
+	 * @dataProvider data_query_filter_posts_results
+	 */
+	public function test_query_filter_posts_results( $filter ) {
+		global $wpdb;
+
+		$args = array(
+			'update_post_meta_cache' => false,
+			'update_post_term_cache' => false,
+			'no_found_rows'          => true,
+		);
+
+		add_filter( $filter, array( $this, 'filter_posts_results' ) );
+
+		$before = get_num_queries();
+		$query1 = new WP_Query();
+		$posts1 = $query1->query( $args );
+		$after  = get_num_queries();
+
+		$this->assertCount( 1, $posts1 );
+
+		$this->assertSame( 2, $after - $before, 'There should only be 2 queries run, one for request and one prime post objects.' );
+
+		$this->assertStringContainsString(
+			"SELECT $wpdb->posts.*",
+			$wpdb->last_query,
+			'Check that _prime_post_caches is called.'
+		);
+	}
+
+	public function filter_posts_results() {
+		return array( get_post( self::$posts[0] ) );
+	}
+
+	public function data_query_filter_posts_results() {
+		return array(
+			array( 'posts_results' ),
+			array( 'the_posts' ),
+		);
+	}
+
 	/**
 	 * @ticket 22176
 	 */