restore _clean_link method from collector.py to pass tests

tests/unit/test_collector.py

@@ -27,12 +27,27 @@
 from pip._internal.index.sources import _FlatDirectorySource, _IndexDirectorySource
 from pip._internal.models.candidate import InstallationCandidate
 from pip._internal.models.index import PyPI
-from pip._internal.models.link import Link, _clean_link, _clean_url_path
+from pip._internal.models.link import Link, _clean_url_path
 from pip._internal.network.session import PipSession
 from tests.lib import TestData, make_test_link_collector
 from tests.lib.path import Path
 
 
+def _clean_link(url: str) -> str:
+    """
+    Make sure a link is fully quoted.
+    For example, if ' ' occurs in the URL, it will be replaced with "%20",
+    and without double-quoting other characters.
+    """
+    # Split the URL into parts according to the general structure
+    # `scheme://netloc/path;parameters?query#fragment`.
+    result = urllib.parse.urlparse(url)
+    # If the netloc is empty, then the URL refers to a local filesystem path.
+    is_local_path = not result.netloc
+    path = _clean_url_path(result.path, is_local_path=is_local_path)
+    return urllib.parse.urlunparse(result._replace(path=path))
+
+
 @pytest.mark.parametrize(
     "url",
     [
@@ -414,7 +429,7 @@ def test_clean_url_path_with_local_path(path: str, expected: str) -> None:
     ],
 )
 def test_clean_link(url: str, clean_url: str) -> None:
-    assert _clean_link(Link(url)).parsed == urllib.parse.urlsplit(clean_url)
+    assert _clean_link(url) == clean_url
 
 
 def _test_parse_links_data_attribute(