[utils] Add convenience urljoin

test/test_utils.py

@@ -70,6 +70,7 @@ from youtube_dl.utils import (
     lowercase_escape,
     url_basename,
     base_url,
+    urljoin,
     urlencode_postdata,
     urshift,
     update_url_query,
@@ -445,6 +446,19 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(base_url('http://foo.de/bar/baz'), 'http://foo.de/bar/')
         self.assertEqual(base_url('http://foo.de/bar/baz?x=z/x/c'), 'http://foo.de/bar/')
 
+    def test_urljoin(self):
+        self.assertEqual(urljoin('http://foo.de/', '/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('http://foo.de/', 'a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('http://foo.de', '/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('http://foo.de', 'a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('http://foo.de/', 'http://foo.de/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin(None, 'http://foo.de/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('', 'http://foo.de/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin(['foobar'], 'http://foo.de/a/b/c.txt'), 'http://foo.de/a/b/c.txt')
+        self.assertEqual(urljoin('http://foo.de/', None), None)
+        self.assertEqual(urljoin('http://foo.de/', ''), None)
+        self.assertEqual(urljoin('http://foo.de/', ['foobar']), None)
+
     def test_parse_age_limit(self):
         self.assertEqual(parse_age_limit(None), None)
         self.assertEqual(parse_age_limit(False), None)

youtube_dl/utils.py

@@ -1700,6 +1700,16 @@ def base_url(url):
     return re.match(r'https?://[^?#&]+/', url).group()
 
 
+def urljoin(base, path):
+    if not isinstance(path, compat_str) or not path:
+        return None
+    if re.match(r'https?://', path):
+        return path
+    if not isinstance(base, compat_str) or not re.match(r'https?://', base):
+        return None
+    return compat_urlparse.urljoin(base, path)
+
+
 class HEADRequest(compat_urllib_request.Request):
     def get_method(self):
         return 'HEAD'