Add a front end JQuery enqueue check

checks/class-jquery-check.php

@@ -0,0 +1,84 @@
+<?php
+/**
+ * Checks if jQuery is loaded by the theme.
+ *
+ * @package Theme Check
+ */
+
+/**
+ * Checks if jQuery is loaded by the theme.
+ *
+ * Themes load jQuery both by enqueueing it directly and by listing it as a dependency
+ * of one of their own scripts, so both cases are reported.
+ */
+class JQuery_Check implements themecheck {
+	/**
+	 * Error messages, warnings and info notices.
+	 *
+	 * @var array $error
+	 */
+	protected $error = array();
+
+	/**
+	 * Check that return true for good/okay/acceptable, false for bad/not-okay/unacceptable.
+	 *
+	 * @param array $php_files File paths and content for PHP files.
+	 * @param array $css_files File paths and content for CSS files.
+	 * @param array $other_files Folder names, file paths and content for other files.
+	 */
+	public function check( $php_files, $css_files, $other_files ) {
+		/*
+		 * The jQuery script handles registered by WordPress: `jquery` itself, the
+		 * `jquery-core` and `jquery-migrate` scripts it is built from, and the
+		 * `jquery-ui-*` family, every member of which depends on `jquery`. Enqueueing
+		 * any of them - or depending on any of them - results in jQuery being loaded.
+		 */
+		$handle = 'jquery(?:-core|-migrate|-ui-[a-z0-9_-]+)?';
+
+		// jQuery enqueued directly, for example wp_enqueue_script( 'jquery' ).
+		$direct_regex = '/\bwp_enqueue_script\s*\(\s*([\'"])' . $handle . '\1/i';
+
+		/*
+		 * jQuery pulled in as a dependency of another script, for example
+		 * wp_enqueue_script( 'theme-script', $src, array( 'jquery' ), $ver, true ) or the
+		 * short array syntax [ 'jquery' ]. `[^;]` keeps the match inside a single
+		 * statement, so the dependency list has to belong to the call that opened it.
+		 */
+		$dependency_regex = '/\bwp_(?:enqueue|register)_script\s*\([^;]{0,300}?(?:array\s*\(|\[)[^)\]]*?([\'"])' . $handle . '\1/i';
+
+		checkcount();
+
+		foreach ( $php_files as $file_path => $file_content ) {
+			if ( ! preg_match( $direct_regex, $file_content ) && ! preg_match( $dependency_regex, $file_content ) ) {
+				continue;
+			}
+
+			$grep = tc_preg( '/jquery/i', $file_path );
+
+			$this->error[] = sprintf(
+				'<span class="tc-lead tc-recommended">%s</span>: %s %s',
+				__( 'RECOMMENDED', 'theme-check' ),
+				sprintf(
+					/* translators: 1: file name, 2: URL of an article about the performance impact of jQuery. */
+					__( 'jQuery is loaded by %1$s, either enqueued directly or listed as a dependency of another script. You may not need it, see <a href="%2$s">this article</a> for tips on switching to vanilla JavaScript.', 'theme-check' ),
+					'<strong>' . tc_filename( $file_path ) . '</strong>',
+					'https://make.wordpress.org/themes/2021/10/04/the-performance-impact-of-using-jquery-in-wordpress-themes/'
+				),
+				$grep
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * Get error messages from the checks.
+	 *
+	 * @return array Error message.
+	 */
+	public function getError() {
+		return $this->error;
+	}
+}
+
+$themechecks[] = new JQuery_Check();