Small speed up to normalizing the path (#1137)

Author: bdraco

CHANGES/1137.misc.rst

@@ -0,0 +1 @@
+Improved performance of normalizing paths -- by :user:`bdraco`.

tests/test_normalize_path.py

@@ -8,13 +8,15 @@
     ("/", "/"),
     ("//", "//"),
     ("///", "///"),
+    ("path", "path"),
     # Single-dot
     ("path/to", "path/to"),
     ("././path/to", "path/to"),
     ("path/./to", "path/to"),
     ("path/././to", "path/to"),
     ("path/to/.", "path/to/"),
     ("path/to/./.", "path/to/"),
+    ("/path/to/.", "/path/to/"),
     # Double-dots
     ("../path/to", "path/to"),
     ("path/../to", "to"),

tests/test_url.py

@@ -993,6 +993,35 @@ def test_joinpath_path_starting_from_slash_is_forbidden():
         assert url.joinpath("/to/others")
 
 
+PATHS = [
+    # No dots
+    ("", ""),
+    ("path", "path"),
+    # Single-dot
+    ("path/to", "path/to"),
+    ("././path/to", "path/to"),
+    ("path/./to", "path/to"),
+    ("path/././to", "path/to"),
+    ("path/to/.", "path/to/"),
+    ("path/to/./.", "path/to/"),
+    # Double-dots
+    ("../path/to", "path/to"),
+    ("path/../to", "to"),
+    ("path/../../to", "to"),
+    # Non-ASCII characters
+    ("μονοπάτι/../../να/ᴜɴɪ/ᴄᴏᴅᴇ", "να/ᴜɴɪ/ᴄᴏᴅᴇ"),
+    ("μονοπάτι/../../να/𝕦𝕟𝕚/𝕔𝕠𝕕𝕖/.", "να/𝕦𝕟𝕚/𝕔𝕠𝕕𝕖/"),
+]
+
+
+@pytest.mark.parametrize("original,expected", PATHS)
+def test_join_path_normalized(original: str, expected: str) -> None:
+    """Test that joinpath normalizes paths."""
+    base_url = URL("http://example.com")
+    new_url = base_url.joinpath(original)
+    assert new_url.path == f"/{expected}"
+
+
 # with_path
 
 

yarl/_url.py

@@ -899,9 +899,12 @@ def _make_child(self, paths: "Sequence[str]", encoded: bool = False) -> "URL":
     @classmethod
     def _normalize_path(cls, path: str) -> str:
         # Drop '.' and '..' from str path
+        if "." not in path:
+            # No need to normalize if there are no '.' or '..' segments
+            return path
 
         prefix = ""
-        if path.startswith("/"):
+        if path and path[0] == "/":
             # preserve the "/" root element of absolute paths, copying it to the
             # normalised output as per sections 5.2.4 and 6.2.2.3 of rfc3986.
             prefix = "/"