gh-88500: Reduce memory use of urllib.unquote

Lib/test/test_urllib.py

@@ -1104,6 +1104,8 @@ def test_unquoting(self):
         self.assertEqual(result.count('%'), 1,
                          "using unquote(): not all characters escaped: "
                          "%s" % result)
+
+    def test_unquote_rejects_none_and_tuple(self):
         self.assertRaises((TypeError, AttributeError), urllib.parse.unquote, None)
         self.assertRaises((TypeError, AttributeError), urllib.parse.unquote, ())
 

Lib/urllib/parse.py

@@ -600,6 +600,9 @@ def urldefrag(url):
 
 def unquote_to_bytes(string):
     """unquote_to_bytes('abc%20def') -> b'abc def'."""
+    return bytes(_unquote_impl(string))
+
+def _unquote_impl(string: bytes | bytearray | str) -> bytes | bytearray:
     # Note: strings are encoded as UTF-8. This is only an issue if it contains
     # unescaped non-ASCII characters, which URIs should not.
     if not string:
@@ -611,8 +614,8 @@ def unquote_to_bytes(string):
     bits = string.split(b'%')
     if len(bits) == 1:
         return string
-    res = [bits[0]]
-    append = res.append
+    res = bytearray(bits[0])
+    append = res.extend
     # Delay the initialization of the table to not waste memory
     # if the function is never called
     global _hextobyte
@@ -626,10 +629,20 @@ def unquote_to_bytes(string):
         except KeyError:
             append(b'%')
             append(item)
-    return b''.join(res)
+    return res
 
 _asciire = re.compile('([\x00-\x7f]+)')
 
+def _generate_unquoted_parts(string, encoding, errors):
+    previous_match_end = 0
+    for ascii_match in _asciire.finditer(string):
+        start, end = ascii_match.span()
+        yield string[previous_match_end:start]  # Non-ASCII
+        # The ascii_match[1] group == string[start:end].
+        yield _unquote_impl(ascii_match[1]).decode(encoding, errors)
+        previous_match_end = end
+    yield string[previous_match_end:]  # Non-ASCII tail
+
 def unquote(string, encoding='utf-8', errors='replace'):
     """Replace %xx escapes by their single-character equivalent. The optional
     encoding and errors parameters specify how to decode percent-encoded
@@ -641,21 +654,16 @@ def unquote(string, encoding='utf-8', errors='replace'):
     unquote('abc%20def') -> 'abc def'.
     """
     if isinstance(string, bytes):
-        return unquote_to_bytes(string).decode(encoding, errors)
+        return _unquote_impl(string).decode(encoding, errors)
     if '%' not in string:
+        # Is it a string-like object?
         string.split
         return string
     if encoding is None:
         encoding = 'utf-8'
     if errors is None:
         errors = 'replace'
-    bits = _asciire.split(string)
-    res = [bits[0]]
-    append = res.append
-    for i in range(1, len(bits), 2):
-        append(unquote_to_bytes(bits[i]).decode(encoding, errors))
-        append(bits[i + 1])
-    return ''.join(res)
+    return ''.join(_generate_unquoted_parts(string, encoding, errors))
 
 
 def parse_qs(qs, keep_blank_values=False, strict_parsing=False,

Misc/NEWS.d/next/Library/2022-09-16-08-21-46.gh-issue-88500.jQ0pCc.rst

@@ -0,0 +1,2 @@
+Reduced the memory usage of :func:`urllib.parse.unquote` and
+:func:`urllib.parse.unquote_to_bytes` on large values.