gh-76960: Fix urljoin() and urldefrag() for URIs with empty components (GH-123273)

* urljoin() with relative reference "?" sets empty query and removes fragment.
* Preserve empty components (authority, params, query, fragment) in urljoin().
* Preserve empty components (authority, params, query) in urldefrag().

Also refactor the code and get rid of double _coerce_args() and
_coerce_result() calls in urljoin(), urldefrag(), urlparse() and
urlunparse().

Lib/test/test_urlparse.py

@@ -349,7 +349,7 @@ class UrlParseTestCase(unittest.TestCase):
                     split = (scheme,) + split
                     self.checkRoundtrips(url, parsed, split)
 
-    def checkJoin(self, base, relurl, expected):
+    def checkJoin(self, base, relurl, expected, *, relroundtrip=True):
         with self.subTest(base=base, relurl=relurl):
             self.assertEqual(urllib.parse.urljoin(base, relurl), expected)
             baseb = base.encode('ascii')
@@ -357,10 +357,11 @@ class UrlParseTestCase(unittest.TestCase):
             expectedb = expected.encode('ascii')
             self.assertEqual(urllib.parse.urljoin(baseb, relurlb), expectedb)
 
-            relurl = urllib.parse.urlunsplit(urllib.parse.urlsplit(relurl))
+            if relroundtrip:
-            self.assertEqual(urllib.parse.urljoin(base, relurl), expected)
+                relurl = urllib.parse.urlunsplit(urllib.parse.urlsplit(relurl))
-            relurlb = urllib.parse.urlunsplit(urllib.parse.urlsplit(relurlb))
+                self.assertEqual(urllib.parse.urljoin(base, relurl), expected)
-            self.assertEqual(urllib.parse.urljoin(baseb, relurlb), expectedb)
+                relurlb = urllib.parse.urlunsplit(urllib.parse.urlsplit(relurlb))
+                self.assertEqual(urllib.parse.urljoin(baseb, relurlb), expectedb)
 
     def test_unparse_parse(self):
         str_cases = ['Python', './Python','x-newscheme://foo.com/stuff','x://y','x:/y','x:/','/',]
@@ -526,8 +527,6 @@ class UrlParseTestCase(unittest.TestCase):
 
     def test_urljoins(self):
         self.checkJoin(SIMPLE_BASE, 'g:h','g:h')
-        self.checkJoin(SIMPLE_BASE, 'http:g','http://a/b/c/g')
-        self.checkJoin(SIMPLE_BASE, 'http:','http://a/b/c/d')
         self.checkJoin(SIMPLE_BASE, 'g','http://a/b/c/g')
         self.checkJoin(SIMPLE_BASE, './g','http://a/b/c/g')
         self.checkJoin(SIMPLE_BASE, 'g/','http://a/b/c/g/')
@@ -548,8 +547,6 @@ class UrlParseTestCase(unittest.TestCase):
         self.checkJoin(SIMPLE_BASE, 'g/./h','http://a/b/c/g/h')
         self.checkJoin(SIMPLE_BASE, 'g/../h','http://a/b/c/h')
         self.checkJoin(SIMPLE_BASE, 'http:g','http://a/b/c/g')
-        self.checkJoin(SIMPLE_BASE, 'http:','http://a/b/c/d')
-        self.checkJoin(SIMPLE_BASE, 'http:?y','http://a/b/c/d?y')
         self.checkJoin(SIMPLE_BASE, 'http:g?y','http://a/b/c/g?y')
         self.checkJoin(SIMPLE_BASE, 'http:g?y/./x','http://a/b/c/g?y/./x')
         self.checkJoin('http:///', '..','http:///')
@@ -579,6 +576,53 @@ class UrlParseTestCase(unittest.TestCase):
         # issue 23703: don't duplicate filename
         self.checkJoin('a', 'b', 'b')
 
+        # Test with empty (but defined) components.
+        self.checkJoin(RFC1808_BASE, '', 'http://a/b/c/d;p?q#f')
+        self.checkJoin(RFC1808_BASE, '#', 'http://a/b/c/d;p?q#', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, '#z', 'http://a/b/c/d;p?q#z')
+        self.checkJoin(RFC1808_BASE, '?', 'http://a/b/c/d;p?', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, '?#z', 'http://a/b/c/d;p?#z', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, '?y', 'http://a/b/c/d;p?y')
+        self.checkJoin(RFC1808_BASE, ';', 'http://a/b/c/;')
+        self.checkJoin(RFC1808_BASE, ';?y', 'http://a/b/c/;?y')
+        self.checkJoin(RFC1808_BASE, ';#z', 'http://a/b/c/;#z')
+        self.checkJoin(RFC1808_BASE, ';x', 'http://a/b/c/;x')
+        self.checkJoin(RFC1808_BASE, '/w', 'http://a/w')
+        self.checkJoin(RFC1808_BASE, '//', 'http://a/b/c/d;p?q#f')
+        self.checkJoin(RFC1808_BASE, '//#z', 'http://a/b/c/d;p?q#z')
+        self.checkJoin(RFC1808_BASE, '//?y', 'http://a/b/c/d;p?y')
+        self.checkJoin(RFC1808_BASE, '//;x', 'http://;x')
+        self.checkJoin(RFC1808_BASE, '///w', 'http://a/w')
+        self.checkJoin(RFC1808_BASE, '//v', 'http://v')
+        # For backward compatibility with RFC1630, the scheme name is allowed
+        # to be present in a relative reference if it is the same as the base
+        # URI scheme.
+        self.checkJoin(RFC1808_BASE, 'http:', 'http://a/b/c/d;p?q#f')
+        self.checkJoin(RFC1808_BASE, 'http:#', 'http://a/b/c/d;p?q#', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'http:#z', 'http://a/b/c/d;p?q#z')
+        self.checkJoin(RFC1808_BASE, 'http:?', 'http://a/b/c/d;p?', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'http:?#z', 'http://a/b/c/d;p?#z', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'http:?y', 'http://a/b/c/d;p?y')
+        self.checkJoin(RFC1808_BASE, 'http:;', 'http://a/b/c/;')
+        self.checkJoin(RFC1808_BASE, 'http:;?y', 'http://a/b/c/;?y')
+        self.checkJoin(RFC1808_BASE, 'http:;#z', 'http://a/b/c/;#z')
+        self.checkJoin(RFC1808_BASE, 'http:;x', 'http://a/b/c/;x')
+        self.checkJoin(RFC1808_BASE, 'http:/w', 'http://a/w')
+        self.checkJoin(RFC1808_BASE, 'http://', 'http://a/b/c/d;p?q#f')
+        self.checkJoin(RFC1808_BASE, 'http://#z', 'http://a/b/c/d;p?q#z')
+        self.checkJoin(RFC1808_BASE, 'http://?y', 'http://a/b/c/d;p?y')
+        self.checkJoin(RFC1808_BASE, 'http://;x', 'http://;x')
+        self.checkJoin(RFC1808_BASE, 'http:///w', 'http://a/w')
+        self.checkJoin(RFC1808_BASE, 'http://v', 'http://v')
+        # Different scheme is not ignored.
+        self.checkJoin(RFC1808_BASE, 'https:', 'https:', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'https:#', 'https:#', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'https:#z', 'https:#z', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'https:?', 'https:?', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'https:?y', 'https:?y', relroundtrip=False)
+        self.checkJoin(RFC1808_BASE, 'https:;', 'https:;')
+        self.checkJoin(RFC1808_BASE, 'https:;x', 'https:;x')
+
     def test_RFC2732(self):
         str_cases = [
             ('http://Test.python.org:5432/foo/', 'test.python.org', 5432),
@@ -641,16 +685,31 @@ class UrlParseTestCase(unittest.TestCase):
             ('http://python.org/p?q', 'http://python.org/p?q', ''),
             (RFC1808_BASE, 'http://a/b/c/d;p?q', 'f'),
             (RFC2396_BASE, 'http://a/b/c/d;p?q', ''),
+            ('http://a/b/c;p?q#f', 'http://a/b/c;p?q', 'f'),
+            ('http://a/b/c;p?q#', 'http://a/b/c;p?q', ''),
+            ('http://a/b/c;p?q', 'http://a/b/c;p?q', ''),
+            ('http://a/b/c;p?#f', 'http://a/b/c;p?', 'f'),
+            ('http://a/b/c;p#f', 'http://a/b/c;p', 'f'),
+            ('http://a/b/c;?q#f', 'http://a/b/c;?q', 'f'),
+            ('http://a/b/c?q#f', 'http://a/b/c?q', 'f'),
+            ('http:///b/c;p?q#f', 'http:///b/c;p?q', 'f'),
+            ('http:b/c;p?q#f', 'http:b/c;p?q', 'f'),
+            ('http:;?q#f', 'http:;?q', 'f'),
+            ('http:?q#f', 'http:?q', 'f'),
+            ('//a/b/c;p?q#f', '//a/b/c;p?q', 'f'),
+            ('://a/b/c;p?q#f', '://a/b/c;p?q', 'f'),
         ]
         def _encode(t):
             return type(t)(x.encode('ascii') for x in t)
         bytes_cases = [_encode(x) for x in str_cases]
         for url, defrag, frag in str_cases + bytes_cases:
-            result = urllib.parse.urldefrag(url)
+            with self.subTest(url):
-            self.assertEqual(result.geturl(), url)
+                result = urllib.parse.urldefrag(url)
-            self.assertEqual(result, (defrag, frag))
+                hash = '#' if isinstance(url, str) else b'#'
-            self.assertEqual(result.url, defrag)
+                self.assertEqual(result.geturl(), url.rstrip(hash))
-            self.assertEqual(result.fragment, frag)
+                self.assertEqual(result, (defrag, frag))
+                self.assertEqual(result.url, defrag)
+                self.assertEqual(result.fragment, frag)
 
     def test_urlsplit_scoped_IPv6(self):
         p = urllib.parse.urlsplit('http://[FE80::822a:a8ff:fe49:470c%tESt]:1234')

Lib/urllib/parse.py

@@ -392,20 +392,23 @@ def urlparse(url, scheme='', allow_fragments=True):
     Note that % escapes are not expanded.
     """
     url, scheme, _coerce_result = _coerce_args(url, scheme)
-    splitresult = urlsplit(url, scheme, allow_fragments)
+    scheme, netloc, url, params, query, fragment = _urlparse(url, scheme, allow_fragments)
-    scheme, netloc, url, query, fragment = splitresult
+    result = ParseResult(scheme or '', netloc or '', url, params or '', query or '', fragment or '')
-    if scheme in uses_params and ';' in url:
-        url, params = _splitparams(url)
-    else:
-        params = ''
-    result = ParseResult(scheme, netloc, url, params, query, fragment)
     return _coerce_result(result)
 
-def _splitparams(url):
+def _urlparse(url, scheme=None, allow_fragments=True):
+    scheme, netloc, url, query, fragment = _urlsplit(url, scheme, allow_fragments)
+    if (scheme or '') in uses_params and ';' in url:
+        url, params = _splitparams(url, allow_none=True)
+    else:
+        params = None
+    return (scheme, netloc, url, params, query, fragment)
+
+def _splitparams(url, allow_none=False):
     if '/'  in url:
         i = url.find(';', url.rfind('/'))
         if i < 0:
-            return url, ''
+            return url, None if allow_none else ''
     else:
         i = url.find(';')
     return url[:i], url[i+1:]
@@ -472,17 +475,23 @@ def urlsplit(url, scheme='', allow_fragments=True):
     """
 
     url, scheme, _coerce_result = _coerce_args(url, scheme)
+    scheme, netloc, url, query, fragment = _urlsplit(url, scheme, allow_fragments)
+    v = SplitResult(scheme or '', netloc or '', url, query or '', fragment or '')
+    return _coerce_result(v)
+
+def _urlsplit(url, scheme=None, allow_fragments=True):
     # Only lstrip url as some applications rely on preserving trailing space.
     # (https://url.spec.whatwg.org/#concept-basic-url-parser would strip both)
     url = url.lstrip(_WHATWG_C0_CONTROL_OR_SPACE)
-    scheme = scheme.strip(_WHATWG_C0_CONTROL_OR_SPACE)
-
     for b in _UNSAFE_URL_BYTES_TO_REMOVE:
         url = url.replace(b, "")
-        scheme = scheme.replace(b, "")
+    if scheme is not None:
+        scheme = scheme.strip(_WHATWG_C0_CONTROL_OR_SPACE)
+        for b in _UNSAFE_URL_BYTES_TO_REMOVE:
+            scheme = scheme.replace(b, "")
 
     allow_fragments = bool(allow_fragments)
-    netloc = query = fragment = ''
+    netloc = query = fragment = None
     i = url.find(':')
     if i > 0 and url[0].isascii() and url[0].isalpha():
         for c in url[:i]:
@@ -503,8 +512,7 @@ def urlsplit(url, scheme='', allow_fragments=True):
     if '?' in url:
         url, query = url.split('?', 1)
     _checknetloc(netloc)
-    v = SplitResult(scheme, netloc, url, query, fragment)
+    return (scheme, netloc, url, query, fragment)
-    return _coerce_result(v)
 
 def urlunparse(components):
     """Put a parsed URL back together again.  This may result in a
@@ -513,9 +521,15 @@ def urlunparse(components):
     (the draft states that these are equivalent)."""
     scheme, netloc, url, params, query, fragment, _coerce_result = (
                                                   _coerce_args(*components))
+    if not netloc:
+        if scheme and scheme in uses_netloc and (not url or url[:1] == '/'):
+            netloc = ''
+        else:
+            netloc = None
     if params:
         url = "%s;%s" % (url, params)
-    return _coerce_result(urlunsplit((scheme, netloc, url, query, fragment)))
+    return _coerce_result(_urlunsplit(scheme or None, netloc, url,
+                                      query or None, fragment or None))
 
 def urlunsplit(components):
     """Combine the elements of a tuple as returned by urlsplit() into a
@@ -525,20 +539,27 @@ def urlunsplit(components):
     empty query; the RFC states that these are equivalent)."""
     scheme, netloc, url, query, fragment, _coerce_result = (
                                           _coerce_args(*components))
-    if netloc:
+    if not netloc:
+        if scheme and scheme in uses_netloc and (not url or url[:1] == '/'):
+            netloc = ''
+        else:
+            netloc = None
+    return _coerce_result(_urlunsplit(scheme or None, netloc, url,
+                                      query or None, fragment or None))
+
+def _urlunsplit(scheme, netloc, url, query, fragment):
+    if netloc is not None:
         if url and url[:1] != '/': url = '/' + url
         url = '//' + netloc + url
     elif url[:2] == '//':
         url = '//' + url
-    elif scheme and scheme in uses_netloc and (not url or url[:1] == '/'):
-        url = '//' + url
     if scheme:
         url = scheme + ':' + url
-    if query:
+    if query is not None:
         url = url + '?' + query
-    if fragment:
+    if fragment is not None:
         url = url + '#' + fragment
-    return _coerce_result(url)
+    return url
 
 def urljoin(base, url, allow_fragments=True):
     """Join a base URL and a possibly relative URL to form an absolute
@@ -549,26 +570,29 @@ def urljoin(base, url, allow_fragments=True):
         return base
 
     base, url, _coerce_result = _coerce_args(base, url)
-    bscheme, bnetloc, bpath, bparams, bquery, bfragment = \
+    bscheme, bnetloc, bpath, bquery, bfragment = \
-            urlparse(base, '', allow_fragments)
+            _urlsplit(base, None, allow_fragments)
-    scheme, netloc, path, params, query, fragment = \
+    scheme, netloc, path, query, fragment = \
-            urlparse(url, bscheme, allow_fragments)
+            _urlsplit(url, None, allow_fragments)
 
+    if scheme is None:
+        scheme = bscheme
     if scheme != bscheme or scheme not in uses_relative:
         return _coerce_result(url)
     if scheme in uses_netloc:
         if netloc:
-            return _coerce_result(urlunparse((scheme, netloc, path,
+            return _coerce_result(_urlunsplit(scheme, netloc, path,
-                                              params, query, fragment)))
+                                              query, fragment))
         netloc = bnetloc
 
-    if not path and not params:
+    if not path:
         path = bpath
-        params = bparams
+        if query is None:
-        if not query:
             query = bquery
-        return _coerce_result(urlunparse((scheme, netloc, path,
+            if fragment is None:
-                                          params, query, fragment)))
+                fragment = bfragment
+        return _coerce_result(_urlunsplit(scheme, netloc, path,
+                                          query, fragment))
 
     base_parts = bpath.split('/')
     if base_parts[-1] != '':
@@ -605,8 +629,8 @@ def urljoin(base, url, allow_fragments=True):
         # then we need to append the trailing '/'
         resolved_path.append('')
 
-    return _coerce_result(urlunparse((scheme, netloc, '/'.join(
+    return _coerce_result(_urlunsplit(scheme, netloc, '/'.join(
-        resolved_path) or '/', params, query, fragment)))
+        resolved_path) or '/', query, fragment))
 
 
 def urldefrag(url):
@@ -618,12 +642,12 @@ def urldefrag(url):
     """
     url, _coerce_result = _coerce_args(url)
     if '#' in url:
-        s, n, p, a, q, frag = urlparse(url)
+        s, n, p, q, frag = _urlsplit(url)
-        defrag = urlunparse((s, n, p, a, q, ''))
+        defrag = _urlunsplit(s, n, p, q, None)
     else:
         frag = ''
         defrag = url
-    return _coerce_result(DefragResult(defrag, frag))
+    return _coerce_result(DefragResult(defrag, frag or ''))
 
 _hexdig = '0123456789ABCDEFabcdef'
 _hextobyte = None

Misc/NEWS.d/next/Library/2024-08-23-22-01-30.gh-issue-76960.vsANPu.rst

@@ -0,0 +1,5 @@
+Fix :func:`urllib.parse.urljoin` and :func:`urllib.parse.urldefrag` for URIs
+containing empty components. For example, :func:`!urljoin()` with relative
+reference "?" now sets empty query and removes fragment.
+Preserve empty components (authority, params, query, fragment) in :func:`!urljoin`.
+Preserve empty components (authority, params, query) in :func:`!urldefrag`.