Fix urlunparse() and urlunsplit() for URIs with path starting with mu…

…ltiple slashes and no authority.

Lib/test/test_urlparse.py

@@ -142,6 +142,30 @@ def test_qs(self):
 
     def test_roundtrips(self):
         str_cases = [
+            ('path/to/file',
+             ('', '', 'path/to/file', '', '', ''),
+             ('', '', 'path/to/file', '', '')),
+            ('/path/to/file',
+             ('', '', '/path/to/file', '', '', ''),
+             ('', '', '/path/to/file', '', '')),
+            ('//path/to/file',
+             ('', 'path', '/to/file', '', '', ''),
+             ('', 'path', '/to/file', '', '')),
+            ('////path/to/file',
+             ('', '', '//path/to/file', '', '', ''),
+             ('', '', '//path/to/file', '', '')),
+            ('scheme:path/to/file',
+             ('scheme', '', 'path/to/file', '', '', ''),
+             ('scheme', '', 'path/to/file', '', '')),
+            ('scheme:/path/to/file',
+             ('scheme', '', '/path/to/file', '', '', ''),
+             ('scheme', '', '/path/to/file', '', '')),
+            ('scheme://path/to/file',
+             ('scheme', 'path', '/to/file', '', '', ''),
+             ('scheme', 'path', '/to/file', '', '')),
+            ('scheme:////path/to/file',
+             ('scheme', '', '//path/to/file', '', '', ''),
+             ('scheme', '', '//path/to/file', '', '')),
             ('file:///tmp/junk.txt',
              ('file', '', '/tmp/junk.txt', '', '', ''),
              ('file', '', '/tmp/junk.txt', '', '')),

Lib/urllib/parse.py

@@ -525,7 +525,7 @@ def urlunsplit(components):
     empty query; the RFC states that these are equivalent)."""
     scheme, netloc, url, query, fragment, _coerce_result = (
                                           _coerce_args(*components))
-    if netloc or (scheme and scheme in uses_netloc):
+    if netloc or (scheme and scheme in uses_netloc) or url[:2] == '//':
         if url and url[:1] != '/': url = '/' + url
         url = '//' + (netloc or '') + url
     if scheme:

Misc/NEWS.d/next/Library/2019-08-27-01-16-50.bpo-34276.4NIAiy.rst

@@ -1 +1,2 @@
-Makes sure that file URIs with multiple leading slashes (file:////, etc.) are properly round-tripped by urllib.parse. Patch by Ashwin Ramaswami
+Fix :func:`urllib.parse.urlunparse` and :func:`urllib.parse.urlunsplit` for URIs with path starting with multiple slashes and no authority.
+Based on patch by Ashwin Ramaswami.