Support for async/defer

Now javascripts are compressed preserving async or defer.

compressor/js.py

@@ -12,14 +12,40 @@ class JsCompressor(Compressor):
     def split_contents(self):
         if self.split_content:
             return self.split_content
+        self.nodes = []
         for elem in self.parser.js_elems():
             attribs = self.parser.elem_attribs(elem)
             if 'src' in attribs:
                 basename = self.get_basename(attribs['src'])
                 filename = self.get_filename(basename)
                 content = (SOURCE_FILE, filename, basename, elem)
-                self.split_content.append(content)
             else:
-                content = self.parser.elem_content(elem)
-                self.split_content.append((SOURCE_HUNK, content, None, elem))
+                content = (SOURCE_HUNK, self.parser.elem_content(elem), None, elem)
+            self.split_content.append(content)
+            extra_attr = ''
+            if 'async' in attribs:
+                extra_attr = ' async'
+            elif 'defer' in attribs:
+                extra_attr = ' defer'
+            # Append to the previous node if it had the same attribute
+            append_to_previous = self.nodes and self.nodes[-1][0] == extra_attr
+            if append_to_previous and settings.COMPRESS_ENABLED:
+                self.nodes[-1][1].split_content.append(content)
+            else:
+                node = JsCompressor(content=self.parser.elem_str(elem),
+                                    context=self.context)
+                node.split_content.append(content)
+                self.nodes.append((extra_attr, node))
         return self.split_content
+
+    def output(self, *args, **kwargs):
+        if (settings.COMPRESS_ENABLED or settings.COMPRESS_PRECOMPILERS or
+                kwargs.get('forced', False)):
+            self.split_contents()
+            if hasattr(self, 'nodes'):
+                ret = []
+                for extra_attr, subnode in self.nodes:
+                    subnode.extra_context.update({'extra_attr': extra_attr})
+                    ret.append(subnode.output(*args, **kwargs))
+                return '\n'.join(ret)
+        return super(JsCompressor, self).output(*args, **kwargs)

compressor/templates/compressor/js_file.html

@@ -1 +1 @@
-<script type="text/javascript" src="{{ compressed.url }}"></script>
+<script type="text/javascript" src="{{ compressed.url }}"{{ compressed.extra_attr }}></script>

compressor/tests/static/js/three.js

@@ -0,0 +1 @@
+hermanos = {}

compressor/tests/static/js/two.js

@@ -0,0 +1 @@
+pollos = {}

compressor/tests/test_base.py

@@ -252,3 +252,31 @@ class CacheBackendTestCase(CompressorTestCase):
     def test_correct_backend(self):
         from compressor.cache import cache
         self.assertEqual(cache.__class__, locmem.CacheClass)
+
+
+class JsAsyncDeferTestCase(SimpleTestCase):
+    def setUp(self):
+        self.js = """\
+            <script src="/static/js/one.js" type="text/javascript"></script>
+            <script src="/static/js/two.js" type="text/javascript" async></script>
+            <script src="/static/js/three.js" type="text/javascript" defer></script>
+            <script type="text/javascript">obj.value = "value";</script>
+            <script src="/static/js/one.js" type="text/javascript" async></script>
+            <script src="/static/js/two.js" type="text/javascript" async></script>
+            <script src="/static/js/three.js" type="text/javascript"></script>"""
+
+    def test_js_output(self):
+        def extract_attr(tag):
+            if tag.has_attr('async'):
+                return 'async'
+            if tag.has_attr('defer'):
+                return 'defer'
+        js_node = JsCompressor(self.js)
+        output = [None, 'async', 'defer', None, 'async', None]
+        if six.PY3:
+            scripts = make_soup(js_node.output()).find_all('script')
+            attrs = [extract_attr(i) for i in scripts]
+        else:
+            scripts = make_soup(js_node.output()).findAll('script')
+            attrs = [s.get('async') or s.get('defer') for s in scripts]
+        self.assertEqual(output, attrs)

compressor/tests/test_jinja2ext.py

@@ -56,8 +56,7 @@ class TestJinja2CompressorExtension(TestCase):
         self.assertEqual(tag_body, template.render())
 
     def test_empty_tag(self):
-        template = self.env.from_string("""{% compress js %}{% block js %}
-        {% endblock %}{% endcompress %}""")
+        template = self.env.from_string("""{% compress js %}{% block js %}{% endblock %}{% endcompress %}""")
         context = {'STATIC_URL': settings.COMPRESS_URL}
         self.assertEqual('', template.render(context))