Use files instead of junctions on Windows (#11269)

Instead of using junctions, we can just write files that contain (as the
file contents) the target path. This requires a little more finesse in
that, as readers, we need to know where to expect these. But it also
means we get to avoid junctions, which have led to a variety of
confusing behaviors. Further, `replace_symlink` should now be on atomic
on Windows.

Closes #11263.

crates/uv-distribution/src/archive.rs

@@ -1,12 +1,7 @@
-use uv_cache::{ArchiveId, Cache};
+use uv_cache::{ArchiveId, Cache, ARCHIVE_VERSION};
 use uv_distribution_types::Hashed;
 use uv_pypi_types::HashDigest;
 
-/// The version of the archive bucket.
-///
-/// Must be kept in-sync with the version in [`uv_cache::CacheBucket::to_str`].
-const ARCHIVE_VERSION: u8 = 0;
-
 /// An archive (unzipped wheel) that exists in the local cache.
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
 pub struct Archive {

crates/uv-distribution/src/distribution_database.rs

@@ -371,7 +371,7 @@ impl<'a, Context: BuildContext> DistributionDatabase<'a, Context> {
 
         // If the wheel was unzipped previously, respect it. Source distributions are
         // cached under a unique revision ID, so unzipped directories are never stale.
-        match built_wheel.target.canonicalize() {
+        match self.build_context.cache().resolve_link(&built_wheel.target) {
             Ok(archive) => {
                 return Ok(LocalWheel {
                     dist: Dist::Source(dist.clone()),

crates/uv-distribution/src/index/built_wheel_index.rs

@@ -1,6 +1,3 @@
-use crate::index::cached_wheel::CachedWheel;
-use crate::source::{HttpRevisionPointer, LocalRevisionPointer, HTTP_REVISION, LOCAL_REVISION};
-use crate::Error;
 use uv_cache::{Cache, CacheBucket, CacheShard, WheelCache};
 use uv_cache_info::CacheInfo;
 use uv_cache_key::cache_digest;
@@ -8,10 +5,13 @@ use uv_configuration::ConfigSettings;
 use uv_distribution_types::{
     DirectUrlSourceDist, DirectorySourceDist, GitSourceDist, Hashed, PathSourceDist,
 };
-use uv_fs::symlinks;
 use uv_platform_tags::Tags;
 use uv_types::HashStrategy;
 
+use crate::index::cached_wheel::CachedWheel;
+use crate::source::{HttpRevisionPointer, LocalRevisionPointer, HTTP_REVISION, LOCAL_REVISION};
+use crate::Error;
+
 /// A local index of built distributions for a specific source distribution.
 #[derive(Debug)]
 pub struct BuiltWheelIndex<'a> {
@@ -203,8 +203,16 @@ impl<'a> BuiltWheelIndex<'a> {
         let mut candidate: Option<CachedWheel> = None;
 
         // Unzipped wheels are stored as symlinks into the archive directory.
-        for subdir in symlinks(shard) {
-            match CachedWheel::from_built_source(&subdir) {
+        for wheel_dir in uv_fs::entries(shard) {
+            // Ignore any `.lock` files.
+            if wheel_dir
+                .extension()
+                .is_some_and(|ext| ext.eq_ignore_ascii_case("lock"))
+            {
+                continue;
+            }
+
+            match CachedWheel::from_built_source(&wheel_dir, self.cache) {
                 None => {}
                 Some(dist_info) => {
                     // Pick the wheel with the highest priority

crates/uv-distribution/src/index/cached_wheel.rs

@@ -26,7 +26,7 @@ pub struct CachedWheel {
 
 impl CachedWheel {
     /// Try to parse a distribution from a cached directory name (like `typing-extensions-4.8.0-py3-none-any`).
-    pub fn from_built_source(path: impl AsRef<Path>) -> Option<Self> {
+    pub fn from_built_source(path: impl AsRef<Path>, cache: &Cache) -> Option<Self> {
         let path = path.as_ref();
 
         // Determine the wheel filename.
@@ -34,7 +34,7 @@ impl CachedWheel {
         let filename = WheelFilename::from_stem(filename).ok()?;
 
         // Convert to a cached wheel.
-        let archive = path.canonicalize().ok()?;
+        let archive = cache.resolve_link(path).ok()?;
         let entry = CacheEntry::from_path(archive);
         let hashes = Vec::new();
         let cache_info = CacheInfo::default();

crates/uv-distribution/src/index/registry_wheel_index.rs

@@ -6,7 +6,7 @@ use uv_cache::{Cache, CacheBucket, WheelCache};
 use uv_cache_key::cache_digest;
 use uv_configuration::ConfigSettings;
 use uv_distribution_types::{CachedRegistryDist, Hashed, Index, IndexLocations, IndexUrl};
-use uv_fs::{directories, files, symlinks};
+use uv_fs::{directories, files};
 use uv_normalize::PackageName;
 use uv_platform_tags::Tags;
 use uv_types::HashStrategy;
@@ -205,8 +205,16 @@ impl<'a> RegistryWheelIndex<'a> {
                         cache_shard.shard(cache_digest(build_configuration))
                     };
 
-                    for wheel_dir in symlinks(cache_shard) {
-                        if let Some(wheel) = CachedWheel::from_built_source(wheel_dir) {
+                    for wheel_dir in uv_fs::entries(cache_shard) {
+                        // Ignore any `.lock` files.
+                        if wheel_dir
+                            .extension()
+                            .is_some_and(|ext| ext.eq_ignore_ascii_case("lock"))
+                        {
+                            continue;
+                        }
+
+                        if let Some(wheel) = CachedWheel::from_built_source(wheel_dir, cache) {
                             if wheel.filename.compatibility(tags).is_compatible() {
                                 // Enforce hash-checking based on the source distribution.
                                 if revision.satisfies(