Strip URLs out of values before testing them.

Prevents false positives on URL strings containing values we're testing
for.

Closes #17

src/detect-feature-use.js

@@ -6,6 +6,7 @@ var features = require('../data/features')
  * searchfor: string or pattern to search for.
  */
 function isFoundIn (str) {
+  str = stripUrls(str)
   return function find (searchfor) {
     if (searchfor instanceof RegExp) return searchfor.test(str)
     else if (_.isFunction(searchfor)) return searchfor(str)
@@ -14,7 +15,15 @@ function isFoundIn (str) {
 }
 
 /*
- * postcss the use of any of a given list of CSS features.
+ * Strip the contents of url literals so they aren't matched
+ * by our naive substring matching.
+ */
+function stripUrls (str) {
+  return str.replace(/url\([^\)]*\)/g, 'url()')
+}
+
+/**
+ * Detect the use of any of a given list of CSS features.
  * ```
  * var detector = new Detector(featureList)
  * detector.process(css, cb)
@@ -30,7 +39,6 @@ function isFoundIn (str) {
  * }
  * ```
  */
-
 module.exports = class Detector {
 constructor (featureList) {
   this.features = _.pick(features, featureList)

test/detect-feature-use.js

@@ -75,10 +75,13 @@ var runTest = function (tc, cssString, expected, only) {
     detector.process(postcss.parse(cssString), cb)
 
     var res = Object.keys(cb.results).sort()
-    t.deepEqual(res, features)
-
     for (var feature in expected) {
-      t.equal(cb.results[feature].length, expected[feature], 'count of ' + feature)
+      if (expected[feature] === 0) {
+        t.notOk(cb.results[feature])
+      } else {
+        t.deepEqual(res, features)
+        t.equal(cb.results[feature].length, expected[feature], 'count of ' + feature)
+      }
     }
 
     t.end()