axe-core/lib/core/utils/parse-stylesheet.js

Accessibility engine for automated Web UI testing

/**
 * Parse a given stylesheet
 *
 * @method parseStylesheet
 * @memberof axe.utils
 * @param {Object} sheet stylesheet to parse
 * @param {Object} options configuration options object from `axe.utils.parseStylesheets`
 * @param {Array<Number>} priority priority of stylesheet
 * @param {Array<String>} importedUrls list of resolved `@import` urls
 * @param {Boolean} isCrossOrigin boolean denoting if a stylesheet is `cross-origin`, passed for re-parsing `cross-origin` sheets
 * @returns {Promise}
 */
axe.utils.parseStylesheet = function parseStylesheet(
	sheet,
	options,
	priority,
	importedUrls,
	isCrossOrigin = false
) {
	const isSameOrigin = isSameOriginStylesheet(sheet);
	if (isSameOrigin) {
		/**
		 * resolve `same-origin` stylesheet
		 */
		return axe.utils.parseSameOriginStylesheet(
			sheet,
			options,
			priority,
			importedUrls,
			isCrossOrigin
		);
	}

	/**
	 * resolve `cross-origin` stylesheet
	 */
	return axe.utils.parseCrossOriginStylesheet(
		sheet.href,
		options,
		priority,
		importedUrls,
		true // -> isCrossOrigin
	);
};

/**
 * Check if a given stylesheet is from the `same-origin`
 * Note:
 * `sheet.cssRules` throws an error on `cross-origin` stylesheets
 *
 * @param {Object} sheet CSS stylesheet
 * @returns {Boolean}
 */
function isSameOriginStylesheet(sheet) {
	try {
		/*eslint no-unused-vars: 0*/
		const rules = sheet.cssRules;

		/**
		 * Safari, does not throw an error when accessing cssRules property,
		 */
		if (!rules && sheet.href) {
			return false;
		}

		return true;
	} catch (e) {
		return false;
	}
}