Require tests to opt-in to managed Python installation (#10912)

First of all, I want to test automatic managed installs (see #10913) and
need to set that up. Second of all, some tests were _implicitly_
downloading interpreters instead of using the one from their context —
which is unexpected and naughty and very slow.

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

@@ -102,6 +102,9 @@ pub struct TestContext {
     /// Standard filters for this test context.
     filters: Vec<(String, String)>,
 
+    /// Extra environment variables to apply to all commands.
+    extra_env: Vec<(OsString, OsString)>,
+
     #[allow(dead_code)]
     _root: tempfile::TempDir,
 }
@@ -233,6 +236,29 @@ impl TestContext {
         self
     }
 
+    /// Add extra directories and configuration for managed Python installations.
+    #[must_use]
+    pub fn with_managed_python_dirs(mut self) -> Self {
+        let managed = self.temp_dir.join("managed");
+        let bin = self.temp_dir.join("bin");
+
+        self.extra_env.push((
+            EnvVars::PATH.into(),
+            env::join_paths(std::iter::once(bin.clone()).chain(env::split_paths(
+                &env::var(EnvVars::PATH).unwrap_or_default(),
+            )))
+            .unwrap(),
+        ));
+        self.extra_env
+            .push((EnvVars::UV_PYTHON_BIN_DIR.into(), bin.into()));
+        self.extra_env
+            .push((EnvVars::UV_PYTHON_INSTALL_DIR.into(), managed.into()));
+        self.extra_env
+            .push((EnvVars::UV_PYTHON_DOWNLOADS.into(), "automatic".into()));
+
+        self
+    }
+
     /// Discover the path to the XDG state directory. We use this, rather than the OS-specific
     /// temporary directory, because on macOS (and Windows on GitHub Actions), they involve
     /// symlinks. (On macOS, the temporary directory is, like `/var/...`, which resolves to
@@ -456,6 +482,7 @@ impl TestContext {
             python_version,
             python_versions,
             filters,
+            extra_env: vec![],
             _root: root,
         }
     }
@@ -510,12 +537,18 @@ impl TestContext {
             .env(EnvVars::PATH, path)
             .env(EnvVars::HOME, self.home_dir.as_os_str())
             .env(EnvVars::UV_PYTHON_INSTALL_DIR, "")
+            // Installations are not allowed by default; see `Self::with_managed_python_dirs`
+            .env(EnvVars::UV_PYTHON_DOWNLOADS, "never")
             .env(EnvVars::UV_TEST_PYTHON_PATH, self.python_path())
             .env(EnvVars::UV_EXCLUDE_NEWER, EXCLUDE_NEWER)
             .env_remove(EnvVars::UV_CACHE_DIR)
             .env_remove(EnvVars::UV_TOOL_BIN_DIR)
             .current_dir(self.temp_dir.path());
 
+        for (key, value) in &self.extra_env {
+            command.env(key, value);
+        }
+
         if activate_venv {
             command.env(EnvVars::VIRTUAL_ENV, self.venv.as_os_str());
         }
@@ -677,21 +710,10 @@ impl TestContext {
     /// Create a `uv python install` command with options shared across scenarios.
     pub fn python_install(&self) -> Command {
         let mut command = self.new_command();
-        let managed = self.temp_dir.join("managed");
-        let bin = self.temp_dir.join("bin");
         self.add_shared_args(&mut command, true);
         command
             .arg("python")
             .arg("install")
-            .env(EnvVars::UV_PYTHON_INSTALL_DIR, managed)
-            .env(EnvVars::UV_PYTHON_BIN_DIR, bin.as_os_str())
-            .env(
-                EnvVars::PATH,
-                env::join_paths(std::iter::once(bin).chain(env::split_paths(
-                    &env::var(EnvVars::PATH).unwrap_or_default(),
-                )))
-                .unwrap(),
-            )
             .current_dir(&self.temp_dir);
         command
     }
@@ -699,14 +721,10 @@ impl TestContext {
     /// Create a `uv python uninstall` command with options shared across scenarios.
     pub fn python_uninstall(&self) -> Command {
         let mut command = self.new_command();
-        let managed = self.temp_dir.join("managed");
-        let bin = self.temp_dir.join("bin");
         self.add_shared_args(&mut command, true);
         command
             .arg("python")
             .arg("uninstall")
-            .env(EnvVars::UV_PYTHON_INSTALL_DIR, managed)
-            .env(EnvVars::UV_PYTHON_BIN_DIR, bin)
             .current_dir(&self.temp_dir);
         command
     }

crates/uv/tests/it/lock_conflict.rs

@@ -3394,7 +3394,7 @@ fn shared_optional_dependency_mixed1() -> Result<()> {
 /// Regression test for: <https://github.com/astral-sh/uv/issues/9640>
 #[test]
 fn shared_optional_dependency_extra2() -> Result<()> {
-    let context = TestContext::new("3.12");
+    let context = TestContext::new("3.11");
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(
@@ -3432,9 +3432,6 @@ fn shared_optional_dependency_extra2() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    Using CPython 3.11.11
-    Removed virtual environment at: .venv
-    Creating virtual environment at: .venv
     Resolved 5 packages in [TIME]
     Prepared 3 packages in [TIME]
     Installed 3 packages in [TIME]
@@ -3536,7 +3533,7 @@ fn shared_optional_dependency_extra2() -> Result<()> {
 /// Regression test for: <https://github.com/astral-sh/uv/issues/9640>
 #[test]
 fn shared_optional_dependency_group2() -> Result<()> {
-    let context = TestContext::new("3.12");
+    let context = TestContext::new("3.11");
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(
@@ -3574,9 +3571,6 @@ fn shared_optional_dependency_group2() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    Using CPython 3.11.11
-    Removed virtual environment at: .venv
-    Creating virtual environment at: .venv
     Resolved 5 packages in [TIME]
     Prepared 3 packages in [TIME]
     Installed 3 packages in [TIME]
@@ -3682,7 +3676,7 @@ fn shared_optional_dependency_group2() -> Result<()> {
 /// Regression test for: <https://github.com/astral-sh/uv/issues/9640>
 #[test]
 fn shared_optional_dependency_mixed2() -> Result<()> {
-    let context = TestContext::new("3.12");
+    let context = TestContext::new("3.11");
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(
@@ -3722,9 +3716,6 @@ fn shared_optional_dependency_mixed2() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    Using CPython 3.11.11
-    Removed virtual environment at: .venv
-    Creating virtual environment at: .venv
     Resolved 5 packages in [TIME]
     Prepared 3 packages in [TIME]
     Installed 3 packages in [TIME]
@@ -4364,7 +4355,7 @@ fn shared_dependency_mixed() -> Result<()> {
 /// Ref <https://github.com/astral-sh/uv/issues/9289>
 #[test]
 fn extras_are_namespaced() -> Result<()> {
-    let context = TestContext::new("3.12");
+    let context = TestContext::new("3.11");
 
     let root_pyproject_toml = context.temp_dir.child("pyproject.toml");
     root_pyproject_toml.write_str(
@@ -4423,9 +4414,6 @@ conflicts = [
     ----- stdout -----
 
     ----- stderr -----
-    Using CPython 3.11.11
-    Removed virtual environment at: .venv
-    Creating virtual environment at: .venv
     Resolved 7 packages in [TIME]
     Prepared 3 packages in [TIME]
     Installed 3 packages in [TIME]
@@ -7297,7 +7285,7 @@ fn deduplicate_resolution_markers() -> Result<()> {
 
 #[test]
 fn overlapping_resolution_markers() -> Result<()> {
-    let context = TestContext::new("3.12");
+    let context = TestContext::new("3.10");
 
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(
@@ -7305,7 +7293,7 @@ fn overlapping_resolution_markers() -> Result<()> {
         [project]
         name = "ads-mega-model"
         version = "0.1.0"
-        requires-python = "==3.10.12"
+        requires-python = "==3.10.*"
         dependencies = [
             "wandb==0.17.6",
         ]
@@ -7344,7 +7332,6 @@ fn overlapping_resolution_markers() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    Using CPython 3.10.12
     Resolved 45 packages in [TIME]
     "###);
 
@@ -7356,7 +7343,7 @@ fn overlapping_resolution_markers() -> Result<()> {
             lock,
             @r###"
         version = 1
-        requires-python = "==3.10.12"
+        requires-python = "==3.10.*"
         resolution-markers = [
             "sys_platform == 'linux' and extra != 'extra-14-ads-mega-model-cpu' and extra == 'extra-14-ads-mega-model-cu118'",
             "sys_platform != 'linux' and extra != 'extra-14-ads-mega-model-cpu' and extra == 'extra-14-ads-mega-model-cu118'",

crates/uv/tests/it/python_install.rs

@@ -13,7 +13,8 @@ use crate::common::{uv_snapshot, TestContext};
 fn python_install() {
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     // Install the latest version
     uv_snapshot!(context.filters(), context.python_install(), @r###"
@@ -95,7 +96,8 @@ fn python_install() {
 fn python_install_preview() {
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     // Install the latest version
     uv_snapshot!(context.filters(), context.python_install().arg("--preview"), @r###"
@@ -269,7 +271,8 @@ fn python_install_preview() {
 fn python_install_preview_upgrade() {
     let context = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     let bin_python = context
         .temp_dir
@@ -408,7 +411,8 @@ fn python_install_preview_upgrade() {
 fn python_install_freethreaded() {
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     // Install the latest version
     uv_snapshot!(context.filters(), context.python_install().arg("--preview").arg("3.13t"), @r###"
@@ -482,7 +486,8 @@ fn python_install_freethreaded() {
 fn python_install_invalid_request() {
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     // Request something that is not a Python version
     uv_snapshot!(context.filters(), context.python_install().arg("foobar"), @r###"
@@ -519,7 +524,8 @@ fn python_install_invalid_request() {
 fn python_install_default() {
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     let bin_python_minor_13 = context
         .temp_dir
@@ -815,7 +821,7 @@ fn read_link_path(path: &Path) -> String {
 
 #[test]
 fn python_install_unknown() {
-    let context: TestContext = TestContext::new_with_versions(&[]);
+    let context: TestContext = TestContext::new_with_versions(&[]).with_managed_python_dirs();
 
     // An unknown request
     uv_snapshot!(context.filters(), context.python_install().arg("foobar"), @r###"
@@ -848,7 +854,8 @@ fn python_install_preview_broken_link() {
 
     let context: TestContext = TestContext::new_with_versions(&[])
         .with_filtered_python_keys()
-        .with_filtered_exe_suffix();
+        .with_filtered_exe_suffix()
+        .with_managed_python_dirs();
 
     let bin_python = context.temp_dir.child("bin").child("python3.13");
 
@@ -883,7 +890,9 @@ fn python_dylib_install_name_is_patched_on_install() {
     use assert_cmd::assert::OutputAssertExt;
     use uv_python::managed::platform_key_from_env;
 
-    let context: TestContext = TestContext::new_with_versions(&[]).with_filtered_python_keys();
+    let context: TestContext = TestContext::new_with_versions(&[])
+        .with_filtered_python_keys()
+        .with_managed_python_dirs();
 
     // Install the latest version
     context

scripts/packages/anyio_local/.python-version

@@ -0,0 +1 @@
+3.12

scripts/packages/built-by-uv/.python-version

@@ -0,0 +1 @@
+3.12