Only drop build directories on program exit (#14304)

## Summary

This PR ensures that we avoid cleaning up build directories until the
end of a resolve-and-install cycle. It's not bulletproof (since we could
still run into issues with `uv lock` followed by `uv sync` whereby a
build directory gets cleaned up that's still referenced in the `build`
artifacts), but it at least gets PyTorch building without error with `uv
pip install .`, which is a case that's been reported several times.

Closes https://github.com/astral-sh/uv/issues/14269.

Cargo.lock

@@ -5937,7 +5937,9 @@ name = "uv-types"
 version = "0.0.1"
 dependencies = [
  "anyhow",
+ "boxcar",
  "rustc-hash",
+ "tempfile",
  "thiserror 2.0.12",
  "uv-cache",
  "uv-configuration",

crates/uv-build-frontend/src/lib.rs

@@ -862,6 +862,10 @@ impl SourceBuild {
 }
 
 impl SourceBuildTrait for SourceBuild {
+    fn into_build_dir(self) -> TempDir {
+        self.temp_dir
+    }
+
     async fn metadata(&mut self) -> Result<Option<PathBuf>, AnyErrorBuild> {
         Ok(self.get_metadata_without_build().await?)
     }

crates/uv-dispatch/src/lib.rs

@@ -2,15 +2,15 @@
 //! [installer][`uv_installer`] and [build][`uv_build`] through [`BuildDispatch`]
 //! implementing [`BuildContext`].
 
-use std::ffi::{OsStr, OsString};
-use std::path::Path;
-
 use anyhow::{Context, Result};
 use futures::FutureExt;
 use itertools::Itertools;
 use rustc_hash::FxHashMap;
+use std::ffi::{OsStr, OsString};
+use std::path::Path;
 use thiserror::Error;
 use tracing::{debug, instrument, trace};
+
 use uv_build_backend::check_direct_build;
 use uv_build_frontend::{SourceBuild, SourceBuildContext};
 use uv_cache::Cache;
@@ -35,8 +35,8 @@ use uv_resolver::{
     PythonRequirement, Resolver, ResolverEnvironment,
 };
 use uv_types::{
-    AnyErrorBuild, BuildContext, BuildIsolation, BuildStack, EmptyInstalledPackages, HashStrategy,
-    InFlight,
+    AnyErrorBuild, BuildArena, BuildContext, BuildIsolation, BuildStack, EmptyInstalledPackages,
+    HashStrategy, InFlight,
 };
 use uv_workspace::WorkspaceCache;
 
@@ -179,6 +179,10 @@ impl BuildContext for BuildDispatch<'_> {
         &self.shared_state.git
     }
 
+    fn build_arena(&self) -> &BuildArena {
+        &self.shared_state.build_arena
+    }
+
     fn capabilities(&self) -> &IndexCapabilities {
         &self.shared_state.capabilities
     }
@@ -521,6 +525,8 @@ pub struct SharedState {
     index: InMemoryIndex,
     /// The downloaded distributions.
     in_flight: InFlight,
+    /// Build directories for any PEP 517 builds executed during resolution or installation.
+    build_arena: BuildArena,
 }
 
 impl SharedState {
@@ -533,6 +539,7 @@ impl SharedState {
         Self {
             git: self.git.clone(),
             capabilities: self.capabilities.clone(),
+            build_arena: self.build_arena.clone(),
             ..Default::default()
         }
     }
@@ -556,4 +563,9 @@ impl SharedState {
     pub fn capabilities(&self) -> &IndexCapabilities {
         &self.capabilities
     }
+
+    /// Return the [`BuildArena`] used by the [`SharedState`].
+    pub fn build_arena(&self) -> &BuildArena {
+        &self.build_arena
+    }
 }

crates/uv-distribution/src/source/mod.rs

@@ -2276,6 +2276,7 @@ impl<'a, T: BuildContext> SourceDistributionBuilder<'a, T> {
         fs::create_dir_all(&cache_shard)
             .await
             .map_err(Error::CacheWrite)?;
+
         // Try a direct build if that isn't disabled and the uv build backend is used.
         let disk_filename = if let Some(name) = self
             .build_context
@@ -2296,7 +2297,8 @@ impl<'a, T: BuildContext> SourceDistributionBuilder<'a, T> {
             // In the uv build backend, the normalized filename and the disk filename are the same.
             name.to_string()
         } else {
-            self.build_context
+            let builder = self
+                .build_context
                 .setup_build(
                     source_root,
                     subdirectory,
@@ -2313,10 +2315,17 @@ impl<'a, T: BuildContext> SourceDistributionBuilder<'a, T> {
                     self.build_stack.cloned().unwrap_or_default(),
                 )
                 .await
-                .map_err(|err| Error::Build(err.into()))?
-                .wheel(temp_dir.path())
-                .await
-                .map_err(Error::Build)?
+                .map_err(|err| Error::Build(err.into()))?;
+
+            // Build the wheel.
+            let wheel = builder.wheel(temp_dir.path()).await.map_err(Error::Build)?;
+
+            // Store a reference to the build context.
+            self.build_context
+                .build_arena()
+                .push(builder.into_build_dir());
+
+            wheel
         };
 
         // Read the metadata from the wheel.
@@ -2398,6 +2407,11 @@ impl<'a, T: BuildContext> SourceDistributionBuilder<'a, T> {
             return Ok(None);
         };
 
+        // Store a reference to the build context.
+        self.build_context
+            .build_arena()
+            .push(builder.into_build_dir());
+
         // Read the metadata from disk.
         debug!("Prepared metadata for: {source}");
         let content = fs::read(dist_info.join("METADATA"))

crates/uv-types/Cargo.toml

@@ -31,7 +31,9 @@ uv-redacted = { workspace = true }
 uv-workspace = { workspace = true }
 
 anyhow = { workspace = true }
+boxcar = { workspace = true }
 rustc-hash = { workspace = true }
+tempfile = { workspace = true }
 thiserror = { workspace = true }
 
 [features]

crates/uv-types/src/builds.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+use tempfile::TempDir;
 use uv_pep508::PackageName;
 use uv_python::PythonEnvironment;
 
@@ -37,3 +39,14 @@ impl BuildIsolation<'_> {
         }
     }
 }
+
+/// An arena of temporary directories used for builds.
+#[derive(Default, Debug, Clone)]
+pub struct BuildArena(Arc<boxcar::Vec<TempDir>>);
+
+impl BuildArena {
+    /// Push a new temporary directory into the arena.
+    pub fn push(&self, temp_dir: TempDir) {
+        self.0.push(temp_dir);
+    }
+}

crates/uv-types/src/traits.rs

@@ -5,7 +5,9 @@ use std::path::{Path, PathBuf};
 
 use anyhow::Result;
 use rustc_hash::FxHashSet;
+use tempfile::TempDir;
 
+use crate::BuildArena;
 use uv_cache::Cache;
 use uv_configuration::{BuildKind, BuildOptions, BuildOutput, ConfigSettings, SourceStrategy};
 use uv_distribution_filename::DistFilename;
@@ -67,6 +69,9 @@ pub trait BuildContext {
     /// Return a reference to the Git resolver.
     fn git(&self) -> &GitResolver;
 
+    /// Return a reference to the build arena.
+    fn build_arena(&self) -> &BuildArena;
+
     /// Return a reference to the discovered registry capabilities.
     fn capabilities(&self) -> &IndexCapabilities;
 
@@ -148,6 +153,9 @@ pub trait BuildContext {
 /// You can either call only `wheel()` to build the wheel directly, call only `metadata()` to get
 /// the metadata without performing the actual or first call `metadata()` and then `wheel()`.
 pub trait SourceBuildTrait {
+    /// Return the temporary build directory.
+    fn into_build_dir(self) -> TempDir;
+
     /// A wrapper for `uv_build::SourceBuild::get_metadata_without_build`.
     ///
     /// For PEP 517 builds, this calls `prepare_metadata_for_build_wheel`