Fix: Reads only the last sourceMappingURL in the file (#1360)

* Fix: Reads only the last sourceMappingURL in the file (which is the only valid)

* Refactor: Create getAnnotationURL() to get the url of the sourceMap match.

* Minor: Rename some variables for better clarity

* Improvement: Add unit test to catch regressions

Author: emzoumpo

lib/postcss.d.ts

@@ -538,6 +538,7 @@ declare namespace postcss {
     consumer(): mozilla.SourceMapConsumer;
     withContent(): boolean;
     startWith(string: string, start: string): boolean;
+    getAnnotationURL(sourceMapString: string): string;
     loadAnnotation(css: string): void;
     decodeInline(text: string): string;
     loadMap(

lib/previous-map.es6

@@ -71,9 +71,23 @@ class PreviousMap {
     return string.substr(0, start.length) === start
   }
 
+  getAnnotationURL (sourceMapString) {
+    return sourceMapString
+      .match(/\/\*\s*# sourceMappingURL=(.*)\s*\*\//)[1]
+      .trim()
+  }
+
   loadAnnotation (css) {
-    let match = css.match(/\/\*\s*# sourceMappingURL=(.*)\s*\*\//)
-    if (match) this.annotation = match[1].trim()
+    let annotations = css.match(/\/\*\s*# sourceMappingURL=(.*)\s*\*\//mg)
+
+    if (annotations && annotations.length > 0) {
+      // Locate the last sourceMappingURL to avoid picking up
+      // sourceMappingURLs from comments, strings, etc.
+      let lastAnnotation = annotations[annotations.length - 1]
+      if (lastAnnotation) {
+        this.annotation = this.getAnnotationURL(lastAnnotation)
+      }
+    }
   }
 
   decodeInline (text) {

test/previous-map.test.js

@@ -121,7 +121,20 @@ it('reads map from annotation', () => {
   expect(root.source.input.map.root).toEqual(dir)
 })
 
-it('sets uniq name for inline map', () => {
+it('reads only the last map from annotation', () => {
+  let file = path.join(dir, 'c.map')
+  fs.outputFileSync(file, map)
+  let root = parse('a{}' +
+    '\n/*# sourceMappingURL=a.map */' +
+    '\n/*# sourceMappingURL=b.map */' +
+    '\n/*# sourceMappingURL=c.map */',
+  { from: file })
+
+  expect(root.source.input.map.text).toEqual(map)
+  expect(root.source.input.map.root).toEqual(dir)
+})
+
+it('sets unique name for inline map', () => {
   let map2 = {
     version: 3,
     sources: ['a'],