Use cached environments in PEP 723 execution (#4789)

## Summary

This seems like another good candidate for environment caching. If you
run a script repeatedly, we can just use the existing cached
environment.

crates/uv/src/commands/project/environment.rs

@@ -126,4 +126,9 @@ impl CachedEnvironment {
 
         Ok(Self(venv))
     }
+
+    /// Convert the [`EphemeralEnvironment`] into an [`Interpreter`].
+    pub(crate) fn into_interpreter(self) -> Interpreter {
+        self.0.into_interpreter()
+    }
 }

crates/uv/src/commands/project/run.rs

@@ -21,6 +21,7 @@ use uv_requirements::{RequirementsSource, RequirementsSpecification};
 use uv_warnings::warn_user_once;
 
 use crate::commands::pip::operations::Modifications;
+use crate::commands::project::environment::CachedEnvironment;
 use crate::commands::{project, ExitStatus, SharedState};
 use crate::printer::Printer;
 use crate::settings::ResolverInstallerSettings;
@@ -55,19 +56,10 @@ pub(crate) async fn run(
     let state = SharedState::default();
 
     // Determine whether the command to execute is a PEP 723 script.
-    let temp_dir;
     let script_interpreter = if let RunCommand::Python(target, _) = &command {
         if let Some(metadata) = uv_scripts::read_pep723_metadata(&target).await? {
             debug!("Found PEP 723 script at: {}", target.display());
 
-            let spec = RequirementsSpecification::from_requirements(
-                metadata
-                    .dependencies
-                    .into_iter()
-                    .map(Requirement::from)
-                    .collect(),
-            );
-
             // (1) Explicit request from user
             let python_request = if let Some(request) = python.as_deref() {
                 Some(PythonRequest::parse(request))
@@ -96,20 +88,15 @@ pub(crate) async fn run(
             .await?
             .into_interpreter();
 
-            // Create a virtual environment
-            temp_dir = cache.environment()?;
-            let venv = uv_virtualenv::create_venv(
-                temp_dir.path(),
-                interpreter,
-                uv_virtualenv::Prompt::None,
-                false,
-                false,
-            )?;
-
             // Install the script requirements.
-            let environment = project::update_environment(
-                venv,
-                spec,
+            let requirements = metadata
+                .dependencies
+                .into_iter()
+                .map(Requirement::from)
+                .collect();
+            let environment = CachedEnvironment::get_or_create(
+                requirements,
+                interpreter,
                 &settings,
                 &state,
                 preview,

crates/uv/tests/run.rs

@@ -223,6 +223,7 @@ fn run_script() -> Result<()> {
        "#
     })?;
 
+    // Running the script should install the requirements.
     uv_snapshot!(context.filters(), context.run().arg("--preview").arg("main.py"), @r###"
         success: true
         exit_code: 0
@@ -235,6 +236,16 @@ fn run_script() -> Result<()> {
          + iniconfig==2.0.0
         "###);
 
+    // Running again should use the existing environment.
+    uv_snapshot!(context.filters(), context.run().arg("--preview").arg("main.py"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###);
+
     // Otherwise, the script requirements should _not_ be available, but the project requirements
     // should.
     let test_non_script = context.temp_dir.child("main.py");