Add source set handling.

macli.py

@@ -25,6 +25,13 @@ OBJECT_TYPE_DESCRIPTORS = (
         'styles',
         'href',
     ),
+    (
+        {
+            'name': 'source'
+        },
+        'sets',
+        'srcset',
+    ),
     (
         {
             'name': 'img'
@@ -94,8 +101,21 @@ def archive(content, base_url, selector, directory, attribute, progbar):
         if part[attribute].startswith('data:'):
             continue
 
-        href = urllib.parse.urljoin(base_url, part[attribute],
-                                    allow_fragments=False)
+        selectors = []
+        if attribute == "srcset":
+            # Dirty hack to support srcset syntax
+            hrefs = []
+            for option in part[attribute].split(','):
+                val, selector = option.split()
+                hrefs.append(urllib.parse.urljoin(base_url, val,
+                                                  allow_fragments=False))
+                selectors.append(selector)
+        else:
+            hrefs = [urllib.parse.urljoin(base_url, part[attribute],
+                                          allow_fragments=False)]
+
+        resolveds = []
+        for i, href in enumerate(hrefs):
             progbar.next_iter(href)
 
             name = (hashlib.sha1(href.encode()).hexdigest()
@@ -114,7 +134,11 @@ def archive(content, base_url, selector, directory, attribute, progbar):
                 with open(path, 'wb') as f:
                     f.write(content)
 
-        part[attribute] = path
+            resolveds.append(path)
+            if i < len(selectors):
+                resolveds[-1] += ' ' + selectors[i]
+
+        part[attribute] = ', '.join(resolveds)
 
 
 def relink_links(content, base_url):