Skip installing --with requirements if present in base environment (#4879)

## Summary

Closes #4547.

crates/uv-installer/src/site_packages.rs

@@ -13,7 +13,7 @@ use distribution_types::{
 use pep440_rs::{Version, VersionSpecifiers};
 use pypi_types::{Requirement, VerbatimParsedUrl};
 use uv_normalize::PackageName;
-use uv_python::PythonEnvironment;
+use uv_python::{Interpreter, PythonEnvironment};
 use uv_types::InstalledPackagesProvider;
 
 use crate::satisfies::RequirementSatisfaction;
@@ -23,7 +23,7 @@ use crate::satisfies::RequirementSatisfaction;
 /// Packages are indexed by both name and (for editable installs) URL.
 #[derive(Debug, Clone)]
 pub struct SitePackages {
-    venv: PythonEnvironment,
+    interpreter: Interpreter,
     /// The vector of all installed distributions. The `by_name` and `by_url` indices index into
     /// this vector. The vector may contain `None` values, which represent distributions that were
     /// removed from the virtual environment.
@@ -37,13 +37,18 @@ pub struct SitePackages {
 }
 
 impl SitePackages {
+    /// Build an index of installed packages from the given Python environment.
+    pub fn from_environment(environment: &PythonEnvironment) -> Result<Self> {
+        Self::from_interpreter(environment.interpreter())
+    }
+
     /// Build an index of installed packages from the given Python executable.
-    pub fn from_environment(venv: &PythonEnvironment) -> Result<SitePackages> {
+    pub fn from_interpreter(interpreter: &Interpreter) -> Result<Self> {
         let mut distributions: Vec<Option<InstalledDist>> = Vec::new();
         let mut by_name = FxHashMap::default();
         let mut by_url = FxHashMap::default();
 
-        for site_packages in venv.site_packages() {
+        for site_packages in interpreter.site_packages() {
             // Read the site-packages directory.
             let site_packages = match fs::read_dir(site_packages) {
                 Ok(site_packages) => {
@@ -66,7 +71,7 @@ impl SitePackages {
                 }
                 Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
                     return Ok(Self {
-                        venv: venv.clone(),
+                        interpreter: interpreter.clone(),
                         distributions,
                         by_name,
                         by_url,
@@ -102,7 +107,7 @@ impl SitePackages {
         }
 
         Ok(Self {
-            venv: venv.clone(),
+            interpreter: interpreter.clone(),
             distributions,
             by_name,
             by_url,
@@ -199,10 +204,10 @@ impl SitePackages {
 
                 // Verify that the package is compatible with the current Python version.
                 if let Some(requires_python) = metadata.requires_python.as_ref() {
-                    if !requires_python.contains(self.venv.interpreter().python_version()) {
+                    if !requires_python.contains(self.interpreter.python_version()) {
                         diagnostics.push(SitePackagesDiagnostic::IncompatiblePythonVersion {
                             package: package.clone(),
-                            version: self.venv.interpreter().python_version().clone(),
+                            version: self.interpreter.python_version().clone(),
                             requires_python: requires_python.clone(),
                         });
                     }
@@ -210,7 +215,7 @@ impl SitePackages {
 
                 // Verify that the dependencies are installed.
                 for dependency in &metadata.requires_dist {
-                    if !dependency.evaluate_markers(self.venv.interpreter().markers(), &[]) {
+                    if !dependency.evaluate_markers(self.interpreter.markers(), &[]) {
                         continue;
                     }
 
@@ -268,7 +273,7 @@ impl SitePackages {
         for entry in requirements {
             if entry
                 .requirement
-                .evaluate_markers(Some(self.venv.interpreter().markers()), &[])
+                .evaluate_markers(Some(self.interpreter.markers()), &[])
             {
                 if seen.insert(entry.clone()) {
                     stack.push(entry.clone());
@@ -323,7 +328,7 @@ impl SitePackages {
                     // Add the dependencies to the queue.
                     for dependency in metadata.requires_dist {
                         if dependency.evaluate_markers(
-                            self.venv.interpreter().markers(),
+                            self.interpreter.markers(),
                             entry.requirement.extras(),
                         ) {
                             let dependency = UnresolvedRequirementSpecification {

crates/uv-python/src/environment.rs

@@ -177,26 +177,7 @@ impl PythonEnvironment {
     /// Some distributions also create symbolic links from `purelib` to `platlib`; in such cases, we
     /// still deduplicate the entries, returning a single path.
     pub fn site_packages(&self) -> impl Iterator<Item = Cow<Path>> {
-        let target = self.0.interpreter.target().map(Target::site_packages);
-
-        let prefix = self
-            .0
-            .interpreter
-            .prefix()
-            .map(|prefix| prefix.site_packages(self.0.interpreter.virtualenv()));
-
-        let interpreter = if target.is_none() && prefix.is_none() {
-            Some(self.0.interpreter.site_packages())
-        } else {
-            None
-        };
-
-        target
-            .into_iter()
-            .flatten()
-            .map(Cow::Borrowed)
-            .chain(prefix.into_iter().flatten().map(Cow::Owned))
-            .chain(interpreter.into_iter().flatten().map(Cow::Borrowed))
+        self.0.interpreter.site_packages()
     }
 
     /// Returns the path to the `bin` directory inside this environment.

crates/uv-python/src/interpreter.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{Command, ExitStatus};
@@ -430,17 +431,40 @@ impl Interpreter {
         }
     }
 
-    /// Return an iterator over the `site-packages` directories inside the environment.
-    pub fn site_packages(&self) -> impl Iterator<Item = &Path> {
-        let purelib = self.purelib();
-        let platlib = self.platlib();
-        std::iter::once(purelib).chain(
-            if purelib == platlib || is_same_file(purelib, platlib).unwrap_or(false) {
-                None
-            } else {
-                Some(platlib)
-            },
-        )
+    /// Returns an iterator over the `site-packages` directories inside the environment.
+    ///
+    /// In most cases, `purelib` and `platlib` will be the same, and so the iterator will contain
+    /// a single element; however, in some distributions, they may be different.
+    ///
+    /// Some distributions also create symbolic links from `purelib` to `platlib`; in such cases, we
+    /// still deduplicate the entries, returning a single path.
+    pub fn site_packages(&self) -> impl Iterator<Item = Cow<Path>> {
+        let target = self.target().map(Target::site_packages);
+
+        let prefix = self
+            .prefix()
+            .map(|prefix| prefix.site_packages(self.virtualenv()));
+
+        let interpreter = if target.is_none() && prefix.is_none() {
+            let purelib = self.purelib();
+            let platlib = self.platlib();
+            Some(std::iter::once(purelib).chain(
+                if purelib == platlib || is_same_file(purelib, platlib).unwrap_or(false) {
+                    None
+                } else {
+                    Some(platlib)
+                },
+            ))
+        } else {
+            None
+        };
+
+        target
+            .into_iter()
+            .flatten()
+            .map(Cow::Borrowed)
+            .chain(prefix.into_iter().flatten().map(Cow::Owned))
+            .chain(interpreter.into_iter().flatten().map(Cow::Borrowed))
     }
 
     /// Check if the interpreter matches the given Python version.

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

@@ -3,6 +3,7 @@ use std::ffi::OsString;
 use std::path::PathBuf;
 
 use anyhow::{Context, Result};
+use itertools::Itertools;
 use tokio::process::Command;
 use tracing::debug;
 
@@ -12,6 +13,7 @@ use uv_cli::ExternalCommand;
 use uv_client::{BaseClientBuilder, Connectivity};
 use uv_configuration::{Concurrency, ExtrasSpecification, PreviewMode};
 use uv_distribution::{VirtualProject, Workspace, WorkspaceError};
+use uv_installer::{SatisfiesResult, SitePackages};
 use uv_normalize::PackageName;
 use uv_python::{
     request_from_version_file, EnvironmentPreference, Interpreter, PythonEnvironment, PythonFetch,
@@ -236,11 +238,65 @@ pub(crate) async fn run(
         );
     }
 
+    // Read the `--with` requirements.
+    let spec = if requirements.is_empty() {
+        None
+    } else {
+        let client_builder = BaseClientBuilder::new()
+            .connectivity(connectivity)
+            .native_tls(native_tls);
+
+        let spec =
+            RequirementsSpecification::from_simple_sources(&requirements, &client_builder).await?;
+
+        Some(spec)
+    };
+
+    // Determine whether the base environment satisfies the ephemeral requirements. If we don't have
+    // any `--with` requirements, and we already have a base environment, then there's no need to
+    // create an additional environment.
+    let skip_ephemeral = base_interpreter.as_ref().is_some_and(|base_interpreter| {
+        let Some(spec) = spec.as_ref() else {
+            return true;
+        };
+
+        let Ok(site_packages) = SitePackages::from_interpreter(base_interpreter) else {
+            return false;
+        };
+
+        if !(settings.reinstall.is_none() && settings.reinstall.is_none()) {
+            return false;
+        }
+
+        match site_packages.satisfies(&spec.requirements, &spec.constraints) {
+            // If the requirements are already satisfied, we're done.
+            Ok(SatisfiesResult::Fresh {
+                recursive_requirements,
+            }) => {
+                debug!(
+                    "Base environment satisfies requirements: {}",
+                    recursive_requirements
+                        .iter()
+                        .map(|entry| entry.requirement.to_string())
+                        .sorted()
+                        .join(" | ")
+                );
+                true
+            }
+            Ok(SatisfiesResult::Unsatisfied(requirement)) => {
+                debug!("At least one requirement is not satisfied in the base environment: {requirement}");
+                false
+            }
+            Err(err) => {
+                debug!("Failed to check requirements against base environment: {err}");
+                false
+            }
+        }
+    });
+
     // If necessary, create an environment for the ephemeral requirements or command.
     let temp_dir;
-    let ephemeral_env = if requirements.is_empty() && base_interpreter.is_some() {
-        // If we don't have any `--with` requirements, and we already have a base environment, then
-        // there's no need to create an additional environment.
+    let ephemeral_env = if skip_ephemeral {
         None
     } else {
         debug!("Creating ephemeral environment");
@@ -351,8 +407,7 @@ pub(crate) async fn run(
                     .as_ref()
                     .map(Interpreter::site_packages)
                     .into_iter()
-                    .flatten()
-                    .map(Cow::Borrowed),
+                    .flatten(),
             )
             .map(PathBuf::from)
             .chain(

crates/uv/tests/run.rs

@@ -326,3 +326,75 @@ fn run_managed_false() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn run_with() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! { r#"
+        [project]
+        name = "foo"
+        version = "1.0.0"
+        requires-python = ">=3.8"
+        dependencies = ["anyio", "sniffio==1.3.1"]
+        "#
+    })?;
+
+    let test_script = context.temp_dir.child("main.py");
+    test_script.write_str(indoc! { r"
+        import sniffio
+       "
+    })?;
+
+    // Requesting an unsatisfied requirement should install it.
+    uv_snapshot!(context.filters(), context.run().arg("--with").arg("iniconfig").arg("main.py"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv run` is experimental and may change without warning.
+    Resolved 6 packages in [TIME]
+    Prepared 4 packages in [TIME]
+    Installed 4 packages in [TIME]
+     + anyio==4.3.0
+     + foo==1.0.0 (from file://[TEMP_DIR]/)
+     + idna==3.6
+     + sniffio==1.3.1
+    Resolved 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.0.0
+    "###);
+
+    // Requesting a satisfied requirement should use the base environment.
+    uv_snapshot!(context.filters(), context.run().arg("--with").arg("sniffio").arg("main.py"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv run` is experimental and may change without warning.
+    Resolved 6 packages in [TIME]
+    Audited 4 packages in [TIME]
+    "###);
+
+    // Unless the user requests a different version.
+    uv_snapshot!(context.filters(), context.run().arg("--with").arg("sniffio<1.3.1").arg("main.py"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv run` is experimental and may change without warning.
+    Resolved 6 packages in [TIME]
+    Audited 4 packages in [TIME]
+    Resolved 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + sniffio==1.3.0
+    "###);
+
+    Ok(())
+}