fix(meta-viewport): parse negative and string values for `maxim… (#2137)

lib/checks/mobile/meta-viewport-scale.js

@@ -1,22 +1,33 @@
-options = options || {};
-var params,
-	content = node.getAttribute('content') || '',
-	parsedParams = content.split(/[;,]/),
-	result = {},
-	minimum = options.scaleMinimum || 2,
-	lowerBound = options.lowerBound || false;
-
-for (var i = 0, l = parsedParams.length; i < l; i++) {
-	params = parsedParams[i].split('=');
-	var key = params.shift().toLowerCase();
-	if (key && params.length) {
-		result[key.trim()] = params
-			.shift()
-			.trim()
-			.toLowerCase();
-	}
+const { scaleMinimum = 2, lowerBound = false } = options || {};
+
+const content = node.getAttribute('content') || '';
+if (!content) {
+	return true;
 }
 
+const result = content.split(/[;,]/).reduce((out, item) => {
+	const contentValue = item.trim();
+	if (!contentValue) {
+		return out;
+	}
+
+	const [key, value] = contentValue.split('=');
+	const curatedKey = key.toLowerCase().trim();
+	let curatedValue = value.toLowerCase().trim();
+
+	// convert `yes` to `1`
+	if (curatedKey === 'maximum-scale' && curatedValue === 'yes') {
+		curatedValue = 1;
+	}
+	// when negative ignore key
+	if (curatedKey === 'maximum-scale' && parseFloat(curatedValue) < 0) {
+		return out;
+	}
+
+	out[curatedKey] = curatedValue;
+	return out;
+}, {});
+
 if (
 	lowerBound &&
 	result['maximum-scale'] &&
@@ -30,7 +41,10 @@ if (!lowerBound && result['user-scalable'] === 'no') {
 	return false;
 }
 
-if (result['maximum-scale'] && parseFloat(result['maximum-scale']) < minimum) {
+if (
+	result['maximum-scale'] &&
+	parseFloat(result['maximum-scale']) < scaleMinimum
+) {
 	this.data('maximum-scale');
 	return false;
 }

test/checks/mobile/meta-viewport-scale.js

@@ -34,6 +34,18 @@ describe('meta-viewport', function() {
 			assert.isTrue(checks['meta-viewport'].evaluate(node));
 		});
 
+		it('should return false on maximum-scale=yes (translates to 1)', function() {
+			fixture.innerHTML = '<meta name="viewport" content="maximum-scale=yes">';
+			var node = fixture.querySelector('meta');
+			assert.isFalse(checks['meta-viewport'].evaluate.call(checkContext, node));
+		});
+
+		it('should return true on negative maximum scale (should be ignored)', function() {
+			fixture.innerHTML = '<meta name="viewport" content="maximum-scale=-1">';
+			var node = fixture.querySelector('meta');
+			assert.isTrue(checks['meta-viewport'].evaluate.call(checkContext, node));
+		});
+
 		it('should return true if maximum-scale >= options.scaleMinimum', function() {
 			fixture.innerHTML =
 				'<meta name="viewport" content="foo=bar, maximum-scale=5, cats=dogs">';