Ignore --find-links entries for pinned indexes (#12396)

## Summary

In general, we merge `--find-links` entries into each index. If a
package is pinned to an index, though, it seems surprising (and wrong)
that we'd ever select a distribution from `--find-links`. This PR
modifies the provider to ignore `--find-links` for any explicitly pinned
packages.

crates/uv-resolver/src/resolver/provider.rs

@@ -160,6 +160,9 @@ impl<Context: BuildContext> ResolverProvider for DefaultResolverProvider<'_, Con
             })
             .await;
 
+        // If a package is pinned to an explicit index, ignore any `--find-links` entries.
+        let flat_index = index.is_none().then_some(&self.flat_index);
+
         match result {
             Ok(results) => Ok(VersionsResponse::Found(
                 results
@@ -174,7 +177,9 @@ impl<Context: BuildContext> ResolverProvider for DefaultResolverProvider<'_, Con
                             &self.allowed_yanks,
                             &self.hasher,
                             self.exclude_newer.as_ref(),
-                            self.flat_index.get(package_name).cloned(),
+                            flat_index
+                                .and_then(|flat_index| flat_index.get(package_name))
+                                .cloned(),
                             self.build_options,
                         )
                     })
@@ -182,23 +187,32 @@ impl<Context: BuildContext> ResolverProvider for DefaultResolverProvider<'_, Con
             )),
             Err(err) => match err.into_kind() {
                 uv_client::ErrorKind::PackageNotFound(_) => {
-                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
+                    if let Some(flat_index) = flat_index
+                        .and_then(|flat_index| flat_index.get(package_name))
+                        .cloned()
+                    {
                         Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
                     } else {
                         Ok(VersionsResponse::NotFound)
                     }
                 }
                 uv_client::ErrorKind::NoIndex(_) => {
-                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
+                    if let Some(flat_index) = flat_index
+                        .and_then(|flat_index| flat_index.get(package_name))
+                        .cloned()
+                    {
                         Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
-                    } else if self.flat_index.offline() {
+                    } else if flat_index.is_some_and(FlatIndex::offline) {
                         Ok(VersionsResponse::Offline)
                     } else {
                         Ok(VersionsResponse::NoIndex)
                     }
                 }
                 uv_client::ErrorKind::Offline(_) => {
-                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
+                    if let Some(flat_index) = flat_index
+                        .and_then(|flat_index| flat_index.get(package_name))
+                        .cloned()
+                    {
                         Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
                     } else {
                         Ok(VersionsResponse::Offline)

crates/uv/tests/it/lock.rs

@@ -9549,6 +9549,126 @@ fn lock_find_links_local_wheel() -> Result<()> {
     Ok(())
 }
 
+/// Prefer an explicit index over any `--find-links` entries.
+#[test]
+fn lock_find_links_explicit_index() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    // Populate the `--find-links` entries.
+    fs_err::create_dir_all(context.temp_dir.join("links"))?;
+
+    for entry in fs_err::read_dir(context.workspace_root.join("scripts/links"))? {
+        let entry = entry?;
+        let path = entry.path();
+        if path
+            .file_name()
+            .and_then(|file_name| file_name.to_str())
+            .is_some_and(|file_name| file_name.starts_with("tqdm-"))
+        {
+            let dest = context
+                .temp_dir
+                .join("links")
+                .join(path.file_name().unwrap());
+            fs_err::copy(&path, &dest)?;
+        }
+    }
+
+    let workspace = context.temp_dir.child("workspace");
+
+    let pyproject_toml = workspace.child("pyproject.toml");
+    pyproject_toml.write_str(&formatdoc! { r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["tqdm"]
+
+        [[tool.uv.index]]
+        name = "pypi"
+        url = "https://pypi.org/simple"
+
+        [tool.uv.sources]
+        tqdm = {{ index = "pypi" }}
+
+        [tool.uv]
+        find-links = ["{}"]
+        "#,
+        context.temp_dir.join("links/").portable_display(),
+    })?;
+
+    uv_snapshot!(context.filters(), context.lock().current_dir(&workspace), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.12.[X] interpreter at: [PYTHON-3.12]
+    Resolved 3 packages in [TIME]
+    ");
+
+    let lock = fs_err::read_to_string(workspace.join("uv.lock")).unwrap();
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r#"
+        version = 1
+        revision = 1
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [[package]]
+        name = "colorama"
+        version = "0.4.6"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/d8/53/6f443c9a4a8358a93a6792e2acffb9d9d5cb0a5cfd8802644b7b1c9a02e4/colorama-0.4.6.tar.gz", hash = "sha256:08695f5cb7ed6e0531a20572697297273c47b8cae5a63ffc6d6ed5c201be6e44", size = 27697 }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/d1/d6/3965ed04c63042e047cb6a3e6ed1a63a35087b6a609aa3a15ed8ac56c221/colorama-0.4.6-py2.py3-none-any.whl", hash = "sha256:4f1d9991f5acc0ca119f9d443620b77f9d6b33703e51011c16baf57afb285fc6", size = 25335 },
+        ]
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { virtual = "." }
+        dependencies = [
+            { name = "tqdm" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "tqdm", index = "https://pypi.org/simple" }]
+
+        [[package]]
+        name = "tqdm"
+        version = "4.66.2"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "colorama", marker = "sys_platform == 'win32'" },
+        ]
+        sdist = { url = "https://files.pythonhosted.org/packages/ea/85/3ce0f9f7d3f596e7ea57f4e5ce8c18cb44e4a9daa58ddb46ee0d13d6bff8/tqdm-4.66.2.tar.gz", hash = "sha256:6cd52cdf0fef0e0f543299cfc96fec90d7b8a7e88745f411ec33eb44d5ed3531", size = 169462 }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/2a/14/e75e52d521442e2fcc9f1df3c5e456aead034203d4797867980de558ab34/tqdm-4.66.2-py3-none-any.whl", hash = "sha256:1ee4f8a893eb9bef51c6e35730cebf234d5d0b6bd112b0271e10ed7c24a02bd9", size = 78296 },
+        ]
+        "#
+        );
+    });
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked").current_dir(&workspace), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.12.[X] interpreter at: [PYTHON-3.12]
+    Resolved 3 packages in [TIME]
+    ");
+
+    Ok(())
+}
+
 /// Lock a local source distribution via `--find-links`.
 #[test]
 fn lock_find_links_local_sdist() -> Result<()> {