From 1e969abb9cef055c5d4350d60532ee63775a1708 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 9 Sep 2024 13:29:01 -0500
Subject: [PATCH] Small speed up to normalizing the path (#1137)

---
 CHANGES/1137.misc.rst        |  1 +
 tests/test_normalize_path.py |  2 ++
 tests/test_url.py            | 29 +++++++++++++++++++++++++++++
 yarl/_url.py                 |  5 ++++-
 4 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 CHANGES/1137.misc.rst

diff --git a/CHANGES/1137.misc.rst b/CHANGES/1137.misc.rst
new file mode 100644
index 000000000..a5abe16e4
--- /dev/null
+++ b/CHANGES/1137.misc.rst
@@ -0,0 +1 @@
+Improved performance of normalizing paths -- by :user:`bdraco`.
diff --git a/tests/test_normalize_path.py b/tests/test_normalize_path.py
index defc4d8dd..20d89818c 100644
--- a/tests/test_normalize_path.py
+++ b/tests/test_normalize_path.py
@@ -8,6 +8,7 @@
     ("/", "/"),
     ("//", "//"),
     ("///", "///"),
+    ("path", "path"),
     # Single-dot
     ("path/to", "path/to"),
     ("././path/to", "path/to"),
@@ -15,6 +16,7 @@
     ("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"),
diff --git a/tests/test_url.py b/tests/test_url.py
index 5f6e033cb..085cf78d8 100644
--- a/tests/test_url.py
+++ b/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
 
 
diff --git a/yarl/_url.py b/yarl/_url.py
index b73562259..effe524e9 100644
--- a/yarl/_url.py
+++ b/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 = "/"