From f892b8564fc3dc2e9c6db4453d8d8860c4a8ba65 Mon Sep 17 00:00:00 2001
From: John Mumm <jtfmumm@gmail.com>
Date: Fri, 27 Jun 2025 19:54:52 +0200
Subject: [PATCH] Return `Cow` from `UrlString::with_` methods (#14319)

A minor performance improvement as a follow-up to #14245 (and an
accompanying test).
---
 crates/uv-distribution-types/src/file.rs | 53 ++++++++++++++----------
 crates/uv-resolver/src/lock/mod.rs       |  8 +++-
 2 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/crates/uv-distribution-types/src/file.rs b/crates/uv-distribution-types/src/file.rs
index 2d30eb0f2..948378c0c 100644
--- a/crates/uv-distribution-types/src/file.rs
+++ b/crates/uv-distribution-types/src/file.rs
@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::fmt::{self, Display, Formatter};
 use std::str::FromStr;
 
@@ -160,27 +161,22 @@ impl UrlString {
             .unwrap_or(self.as_ref())
     }
 
-    /// Return the [`UrlString`] with any fragments removed.
+    /// Return the [`UrlString`] (as a [`Cow`]) with any fragments removed.
     #[must_use]
-    pub fn without_fragment(&self) -> Self {
-        Self(
-            self.as_ref()
-                .split_once('#')
-                .map(|(path, _)| path)
-                .map(SmallString::from)
-                .unwrap_or_else(|| self.0.clone()),
-        )
+    pub fn without_fragment(&self) -> Cow<'_, Self> {
+        self.as_ref()
+            .split_once('#')
+            .map(|(path, _)| Cow::Owned(UrlString(SmallString::from(path))))
+            .unwrap_or(Cow::Borrowed(self))
     }
 
-    /// Return the [`UrlString`] with trailing slash removed.
+    /// Return the [`UrlString`] (as a [`Cow`]) with trailing slash removed.
     #[must_use]
-    pub fn without_trailing_slash(&self) -> Self {
-        Self(
-            self.as_ref()
-                .strip_suffix('/')
-                .map(SmallString::from)
-                .unwrap_or_else(|| self.0.clone()),
-        )
+    pub fn without_trailing_slash(&self) -> Cow<'_, Self> {
+        self.as_ref()
+            .strip_suffix('/')
+            .map(|path| Cow::Owned(UrlString(SmallString::from(path))))
+            .unwrap_or(Cow::Borrowed(self))
     }
 }
 
@@ -263,16 +259,29 @@ mod tests {
 
     #[test]
     fn without_fragment() {
+        // Borrows a URL without a fragment
+        let url = UrlString("https://example.com/path".into());
+        assert_eq!(url.without_fragment(), Cow::Borrowed(&url));
+
+        // Removes the fragment if present on the URL
         let url = UrlString("https://example.com/path?query#fragment".into());
         assert_eq!(
             url.without_fragment(),
-            UrlString("https://example.com/path?query".into())
+            Cow::Owned(UrlString("https://example.com/path?query".into()))
         );
+    }
 
-        let url = UrlString("https://example.com/path#fragment".into());
-        assert_eq!(url.base_str(), "https://example.com/path");
-
+    #[test]
+    fn without_trailing_slash() {
+        // Borrows a URL without a slash
         let url = UrlString("https://example.com/path".into());
-        assert_eq!(url.base_str(), "https://example.com/path");
+        assert_eq!(url.without_trailing_slash(), Cow::Borrowed(&url));
+
+        // Removes the trailing slash if present on the URL
+        let url = UrlString("https://example.com/path/".into());
+        assert_eq!(
+            url.without_trailing_slash(),
+            Cow::Owned(UrlString("https://example.com/path".into()))
+        );
     }
 }
diff --git a/crates/uv-resolver/src/lock/mod.rs b/crates/uv-resolver/src/lock/mod.rs
index 8ff3097de..beeadc912 100644
--- a/crates/uv-resolver/src/lock/mod.rs
+++ b/crates/uv-resolver/src/lock/mod.rs
@@ -1490,7 +1490,11 @@ impl Lock {
                                 .version
                                 .as_ref()
                                 .expect("version for registry source");
-                            return Ok(SatisfiesResult::MissingRemoteIndex(name, version, url));
+                            return Ok(SatisfiesResult::MissingRemoteIndex(
+                                name,
+                                version,
+                                url.into_owned(),
+                            ));
                         }
                     }
                     RegistrySource::Path(path) => {
@@ -4692,7 +4696,7 @@ impl From<Hash> for Hashes {
 /// Convert a [`FileLocation`] into a normalized [`UrlString`].
 fn normalize_file_location(location: &FileLocation) -> Result<UrlString, ToUrlError> {
     match location {
-        FileLocation::AbsoluteUrl(absolute) => Ok(absolute.without_fragment()),
+        FileLocation::AbsoluteUrl(absolute) => Ok(absolute.without_fragment().into_owned()),
         FileLocation::RelativeUrl(_, _) => Ok(normalize_url(location.to_url()?)),
     }
 }