Update theme_has_theme_json to match core-patched version

src/ReaderThemeSupportFeatures.php

@@ -584,31 +584,32 @@ private function theme_has_theme_json() {
 		// return wp_theme_has_theme_json();
 		// }
 
-		static $theme_has_support = null;
+		static $theme_has_support         = null;
+		static $prev_stylesheet_directory = null;
+		static $prev_template_directory   = null;
+
+		$stylesheet_directory = get_stylesheet_directory();
+		$template_directory   = get_template_directory();
+
+		// Make sure that the cached $theme_has_support value is reset when the theme changes.
+		if ( null !== $theme_has_support && (
+				$stylesheet_directory !== $prev_stylesheet_directory ||
+				$template_directory !== $prev_template_directory
+			) ) {
+			$theme_has_support = null;
+		}
+		$prev_stylesheet_directory = $stylesheet_directory;
+		$prev_template_directory   = $template_directory;
 
 		if (
 			null !== $theme_has_support &&
-
-			/*
-			* Ignore static cache when `WP_DEBUG` is enabled. Why? To avoid interfering with
-			* the theme developer's workflow.
-			*
-			* @todo Replace `WP_DEBUG` once an "in development mode" check is available in Core.
-			*/
-			! ( defined( 'WP_DEBUG' ) && WP_DEBUG ) &&
-
-			/*
-			* Ignore cache when automated test suites are running. Why? To ensure
-			* the static cache is reset between each test.
-			*/
-			! ( defined( 'WP_RUN_CORE_TESTS' ) && WP_RUN_CORE_TESTS )
+			// Ignore static cache when the development mode is set to 'theme', to avoid interfering with
+			// the theme developer's workflow.
+			( function_exists( 'wp_get_development_mode' ) && wp_get_development_mode() !== 'theme' )
 		) {
 			return $theme_has_support;
 		}
 
-		$stylesheet_directory = get_stylesheet_directory();
-		$template_directory   = get_template_directory();
-
 		// This is the same as get_theme_file_path(), which isn't available in load-styles.php context.
 		if ( $stylesheet_directory !== $template_directory && file_exists( $stylesheet_directory . '/theme.json' ) ) {
 			$path = $stylesheet_directory . '/theme.json';