Script Loader: Don't check is_feed() before the main query is run in block asset functions.

src/wp-includes/script-loader.php

@@ -3013,6 +3013,32 @@ function wp_should_load_block_editor_scripts_and_styles() {
 	return apply_filters( 'should_load_block_editor_scripts_and_styles', $is_block_editor_screen );
 }
 
+/**
+ * Determines whether the current request is known not to be a front-end page load.
+ *
+ * This is used by {@see wp_should_load_separate_core_block_assets()} and
+ * {@see wp_should_load_block_assets_on_demand()}, which can be called very early (such as at `init` or
+ * `wp_default_styles`) before the main query has been run. Conditional query tags like {@see is_feed()} cannot return
+ * meaningful results until then, so the feed check is only performed once the main query is known.
+ *
+ * @since 7.2.0
+ * @access private
+ *
+ * @return bool Whether the request is for the admin, a feed, or a REST API endpoint.
+ */
+function _wp_is_non_frontend_request_for_block_assets() {
+	if ( is_admin() ) {
+		return true;
+	}
+
+	// The query is only parsed and run by the time the 'wp' action fires.
+	if ( did_action( 'wp' ) && is_feed() ) {
+		return true;
+	}
+
+	return wp_is_rest_endpoint();
+}
+
 /**
  * Checks whether separate styles should be loaded for core blocks.
  *
@@ -3032,7 +3058,7 @@ function wp_should_load_block_editor_scripts_and_styles() {
  * @return bool Whether separate core block assets will be loaded.
  */
 function wp_should_load_separate_core_block_assets() {
-	if ( is_admin() || is_feed() || wp_is_rest_endpoint() ) {
+	if ( _wp_is_non_frontend_request_for_block_assets() ) {
 		return false;
 	}
 
@@ -3067,7 +3093,7 @@ function wp_should_load_separate_core_block_assets() {
  * @return bool Whether to load block assets only when they are rendered.
  */
 function wp_should_load_block_assets_on_demand() {
-	if ( is_admin() || is_feed() || wp_is_rest_endpoint() ) {
+	if ( _wp_is_non_frontend_request_for_block_assets() ) {
 		return false;
 	}
 

tests/phpunit/tests/theme.php

@@ -443,7 +443,7 @@
 	 * @expectedDeprecated get_themes
 	 * @expectedDeprecated get_current_theme
 	 */
 	public function test_switch_theme() {
 		$themes = get_themes();
 
 		$this->assertNotEmpty( $themes );
@@ -1013,6 +1013,44 @@
 		$this->assertTrue( wp_should_load_block_assets_on_demand() );
 	}
 
+	/**
+	 * Tests that the feed check does not apply before the main query has been run.
+	 *
+	 * @ticket 63693
+	 *
+	 * @covers ::wp_should_load_separate_core_block_assets
+	 * @covers ::wp_should_load_block_assets_on_demand
+	 * @covers ::_wp_is_non_frontend_request_for_block_assets
+	 */
+	public function test_block_assets_functions_ignore_feed_before_query_is_run() {
+		add_filter( 'should_load_separate_core_block_assets', '__return_true' );
+		$GLOBALS['wp_query']->is_feed = true;
+
+		$this->assertTrue( wp_should_load_separate_core_block_assets(), 'Feed check should be skipped before the wp action.' );
+		$this->assertTrue( wp_should_load_block_assets_on_demand(), 'Feed check should be skipped before the wp action.' );
+
+		do_action( 'wp' );
+
+		$this->assertFalse( wp_should_load_separate_core_block_assets(), 'Feeds should not load separate assets.' );
+		$this->assertFalse( wp_should_load_block_assets_on_demand(), 'Feeds should not load assets on demand.' );
+	}
+
+	/**
+	 * Tests that a REST endpoint request disables loading block assets separately and on demand.
+	 *
+	 * @ticket 63693
+	 *
+	 * @covers ::wp_should_load_separate_core_block_assets
+	 * @covers ::wp_should_load_block_assets_on_demand
+	 */
+	public function test_block_assets_functions_return_false_for_rest_endpoint() {
+		add_filter( 'should_load_separate_core_block_assets', '__return_true' );
+		add_filter( 'wp_is_rest_endpoint', '__return_true' );
+
+		$this->assertFalse( wp_should_load_separate_core_block_assets() );
+		$this->assertFalse( wp_should_load_block_assets_on_demand() );
+	}
+
 	/**
 	 * Tests that a theme in the custom test data theme directory is recognized.
 	 *