Add test

crates/uv-install-wheel/src/linker.rs

@@ -25,22 +25,28 @@ pub struct Locks {
 
 impl Locks {
     /// Warn when a module exists in multiple packages.
-    fn warn_module_conflict(&self, module: &OsStr, filename: &WheelFilename) {
-        if let Some(existing) = self
+    fn warn_module_conflict(&self, module: &OsStr, wheel_a: &WheelFilename) {
+        if let Some(wheel_b) = self
             .modules
             .lock()
             .unwrap()
-            .insert(module.to_os_string(), filename.clone())
+            .insert(module.to_os_string(), wheel_a.clone())
         {
+            // Sort for consistent output, at least with two packages
+            let (wheel_a, wheel_b) = if wheel_b.name > wheel_a.name {
+                (&wheel_b, wheel_a)
+            } else {
+                (wheel_a, &wheel_b)
+            };
             warn_user!(
                 "The module {} exists in two packages! \
                 This leads to a race condition and likely to a broken installation. \
                 Consider removing either {} ({}) or {} ({}).",
                 module.simplified_display(),
-                existing.name,
-                existing,
-                filename.name,
-                filename,
+                wheel_a.name,
+                wheel_a,
+                wheel_b.name,
+                wheel_b,
             );
         }
     }
@@ -548,7 +554,7 @@ fn synchronized_copy(from: &Path, to: &Path, locks: &Locks) -> std::io::Result<(
 /// Warn when a module exists in multiple packages.
 fn warn_module_conflict(locks: &Locks, filename: &WheelFilename, relative: &Path) {
     // Check for `__init__.py` to account for namespace packages.
-    // TODO(konsti): We need to handle namespace packages, too.
+    // TODO(konsti): We need to warn for overlapping namespace packages, too.
     if relative.components().count() == 2
         && relative.components().next_back().unwrap().as_os_str() == "__init__.py"
     {

crates/uv/tests/it/pip_install.rs

@@ -11350,3 +11350,89 @@ fn pep_751_dependency() -> Result<()> {
 
     Ok(())
 }
+
+/// Check that we warn for overlapping packages but not for correctly overlapping namespace
+/// packages.
+#[test]
+fn overlapping_packages_warning() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    context
+        .build()
+        .arg("--preview")
+        .arg(context.workspace_root.join("scripts/packages/built-by-uv"))
+        .arg("--out-dir")
+        .arg(context.temp_dir.path())
+        .assert()
+        .success();
+
+    // Overlaps with `built-by-uv`
+    let also_build_by_uv = context.temp_dir.child("also-built-by-uv");
+    also_build_by_uv.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "also-built-by-uv"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [tool.uv.build-backend]
+        module-name = "built_by_uv"
+
+        [build-system]
+        requires = ["uv_build>=0.7,<10000"]
+        build-backend = "uv_build"
+        "#,
+    )?;
+    also_build_by_uv
+        .child("src")
+        .child("built_by_uv")
+        .child("__init__.py")
+        .touch()?;
+    context
+        .build()
+        .arg("--preview")
+        .arg(also_build_by_uv.path())
+        .arg("--out-dir")
+        .arg(context.temp_dir.path())
+        .assert()
+        .success();
+
+    // Check that overlapping packages show a warning
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--no-deps")
+        .arg(context.temp_dir.join("built_by_uv-0.1.0-py3-none-any.whl"))
+        .arg(context.temp_dir.join("also_built_by_uv-0.1.0-py3-none-any.whl")), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 2 packages in [TIME]
+    warning: The module built_by_uv exists in two packages! This leads to a race condition and likely to a broken installation. Consider removing either built-by-uv (built_by_uv-0.1.0-py3-none-any.whl) or also-built-by-uv (also_built_by_uv-0.1.0-py3-none-any.whl).
+    Installed 2 packages in [TIME]
+     + also-built-by-uv==0.1.0 (from file://[TEMP_DIR]/also_built_by_uv-0.1.0-py3-none-any.whl)
+     + built-by-uv==0.1.0 (from file://[TEMP_DIR]/built_by_uv-0.1.0-py3-none-any.whl)
+    "
+    );
+
+    // Check that correctly overlapping namespace packages don't show a warning
+    uv_snapshot!(context.pip_install()
+        .arg("--no-deps")
+        .arg("poetry")
+        .arg("poetry-core"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 2 packages in [TIME]
+    Installed 2 packages in [TIME]
+     + poetry==1.8.2
+     + poetry-core==1.9.0
+    "
+    );
+
+    Ok(())
+}