Add test cases

Author: zanieb

crates/uv-python/src/discovery.rs

@@ -446,7 +446,16 @@ fn python_executables_from_installed<'a>(
     .flatten();
 
     match preference {
-        PythonPreference::OnlyManaged => Box::new(from_managed_installations),
+        PythonPreference::OnlyManaged => {
+            // TODO(zanieb): Ideally, we'd create "fake" managed installation directories for tests,
+            // but for now... we'll just include the test interpreters which are always on the
+            // search path.
+            if std::env::var(uv_static::EnvVars::UV_INTERNAL__TEST_PYTHON_MANAGED).is_ok() {
+                Box::new(from_managed_installations.chain(from_search_path))
+            } else {
+                Box::new(from_managed_installations)
+            }
+        }
         PythonPreference::Managed => Box::new(
             from_managed_installations
                 .chain(from_search_path)

crates/uv-python/src/interpreter.rs

@@ -268,6 +268,23 @@ impl Interpreter {
     ///
     /// Returns `false` if we cannot determine the path of the uv managed Python interpreters.
     pub fn is_managed(&self) -> bool {
+        if let Ok(test_managed) =
+            std::env::var(uv_static::EnvVars::UV_INTERNAL__TEST_PYTHON_MANAGED)
+        {
+            // During testing, we collect interpreters into an artificial search path and need to
+            // be able to mock whether an interpreter is managed or not.
+            return test_managed.split_ascii_whitespace().any(|item| {
+                let version = <PythonVersion as std::str::FromStr>::from_str(item).expect(
+                    "`UV_INTERNAL__TEST_PYTHON_MANAGED` items should be valid Python versions",
+                );
+                if version.patch().is_some() {
+                    version.version() == self.python_version()
+                } else {
+                    (version.major(), version.minor()) == self.python_tuple()
+                }
+            });
+        }
+
         let Ok(installations) = ManagedPythonInstallations::from_settings(None) else {
             return false;
         };

crates/uv-static/src/env_vars.rs

@@ -359,6 +359,14 @@ impl EnvVars {
     #[attr_hidden]
     pub const UV_INTERNAL__SHOW_DERIVATION_TREE: &'static str = "UV_INTERNAL__SHOW_DERIVATION_TREE";
 
+    /// Used to set a temporary directory for some tests.
+    #[attr_hidden]
+    pub const UV_INTERNAL__TEST_DIR: &'static str = "UV_INTERNAL__TEST_DIR";
+
+    /// Used to force treating an interpreter as "managed" during tests.
+    #[attr_hidden]
+    pub const UV_INTERNAL__TEST_PYTHON_MANAGED: &'static str = "UV_INTERNAL__TEST_PYTHON_MANAGED";
+
     /// Path to system-level configuration directory on Unix systems.
     pub const XDG_CONFIG_DIRS: &'static str = "XDG_CONFIG_DIRS";
 

crates/uv/tests/it/common/mod.rs

@@ -187,6 +187,18 @@ impl TestContext {
             "virtual environments, managed installations, search path, or registry".to_string(),
             "[PYTHON SOURCES]".to_string(),
         ));
+        self.filters.push((
+            "virtual environments, search path, or registry".to_string(),
+            "[PYTHON SOURCES]".to_string(),
+        ));
+        self.filters.push((
+            "virtual environments, registry, or search path".to_string(),
+            "[PYTHON SOURCES]".to_string(),
+        ));
+        self.filters.push((
+            "virtual environments or search path".to_string(),
+            "[PYTHON SOURCES]".to_string(),
+        ));
         self.filters.push((
             "managed installations or search path".to_string(),
             "[PYTHON SOURCES]".to_string(),
@@ -406,6 +418,15 @@ impl TestContext {
         self
     }
 
+    pub fn with_versions_as_managed(mut self, versions: &[&str]) -> Self {
+        self.extra_env.push((
+            EnvVars::UV_INTERNAL__TEST_PYTHON_MANAGED.into(),
+            versions.iter().join(" ").into(),
+        ));
+
+        self
+    }
+
     /// Clear filters on `TestContext`.
     pub fn clear_filters(mut self) -> Self {
         self.filters.clear();

crates/uv/tests/it/pip_install.rs

@@ -11659,3 +11659,58 @@ fn strip_shebang_arguments() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn install_python_preference() {
+    let context =
+        TestContext::new_with_versions(&["3.12", "3.11"]).with_versions_as_managed(&["3.12"]);
+
+    // Create a managed interpreter environment
+    uv_snapshot!(context.filters(), context.venv(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtual environment at: .venv
+    Activate with: source .venv/[BIN]/activate
+    ");
+
+    // Install a package, requesting managed Python
+    uv_snapshot!(context.filters(), context.pip_install().arg("anyio").arg("--managed-python"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    Prepared 3 packages in [TIME]
+    Installed 3 packages in [TIME]
+     + anyio==4.3.0
+     + idna==3.6
+     + sniffio==1.3.1
+    ");
+
+    // Install a package, requesting unmanaged Python
+    // This is allowed, because the virtual environment already exists
+    uv_snapshot!(context.filters(), context.pip_install().arg("anyio").arg("--no-managed-python"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Audited 1 package in [TIME]
+    ");
+
+    // This also works with `VIRTUAL_ENV` unset
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("anyio").arg("--no-managed-python").env_remove("VIRTUAL_ENV"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Audited 1 package in [TIME]
+    ");
+}

crates/uv/tests/it/python_find.rs

@@ -729,6 +729,57 @@ fn python_find_venv_invalid() {
     "###);
 }
 
+#[test]
+fn python_find_managed() {
+    let context: TestContext = TestContext::new_with_versions(&["3.11", "3.12"])
+        .with_filtered_python_sources()
+        .with_versions_as_managed(&["3.12"]);
+
+    // We find the managed interpreter
+    uv_snapshot!(context.filters(), context.python_find().arg("--managed-python"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [PYTHON-3.12]
+
+    ----- stderr -----
+    ");
+
+    // Request an interpreter that cannot be satisfied
+    uv_snapshot!(context.filters(), context.python_find().arg("--managed-python").arg("3.11"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: No interpreter found for Python 3.11 in virtual environments or managed installations
+    ");
+
+    let context: TestContext = TestContext::new_with_versions(&["3.11", "3.12"])
+        .with_filtered_python_sources()
+        .with_versions_as_managed(&["3.11"]);
+
+    // We find the unmanaged interpreter
+    uv_snapshot!(context.filters(), context.python_find().arg("--no-managed-python"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [PYTHON-3.12]
+
+    ----- stderr -----
+    ");
+
+    // Request an interpreter that cannot be satisfied
+    uv_snapshot!(context.filters(), context.python_find().arg("--no-managed-python").arg("3.11"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: No interpreter found for Python 3.11 in [PYTHON SOURCES]
+    ");
+}
+
 /// See: <https://github.com/astral-sh/uv/issues/11825>
 ///
 /// This test will not succeed on macOS if using a Homebrew provided interpreter. The interpreter

crates/uv/tests/it/run.rs

@@ -5500,3 +5500,49 @@ fn run_no_sync_incompatible_python() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn run_python_preference_no_project() {
+    let context =
+        TestContext::new_with_versions(&["3.12", "3.11"]).with_versions_as_managed(&["3.12"]);
+
+    context.venv().assert().success();
+
+    uv_snapshot!(context.filters(), context.run().arg("python").arg("--version"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.12.[X]
+
+    ----- stderr -----
+    ");
+
+    uv_snapshot!(context.filters(), context.run().arg("--managed-python").arg("python").arg("--version"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.12.[X]
+
+    ----- stderr -----
+    ");
+
+    // `VIRTUAL_ENV` is set here, so we'll ignore the flag
+    uv_snapshot!(context.filters(), context.run().arg("--no-managed-python").arg("python").arg("--version"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.12.[X]
+
+    ----- stderr -----
+    ");
+
+    // If we remove the `VIRTUAL_ENV` variable, we should get the unmanaged Python
+    uv_snapshot!(context.filters(), context.run().arg("--no-managed-python").arg("python").arg("--version").env_remove("VIRTUAL_ENV"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Python 3.11.[X]
+
+    ----- stderr -----
+    ");
+}