Respect reinstalls in cached environments (#5499)

## Summary

Closes #5493.

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

@@ -74,8 +74,10 @@ impl CachedEnvironment {
         // Hash the resolution by hashing the generated lockfile.
         // TODO(charlie): If the resolution contains any mutable metadata (like a path or URL
         // dependency), skip this step.
+        let resolution_hash = {
             let distributions = resolution.distributions().collect::<Vec<_>>();
-        let resolution_hash = hash_digest(&distributions);
+            hash_digest(&distributions)
+        };
 
         // Hash the interpreter based on its path.
         // TODO(charlie): Come up with a robust hash for the interpreter.
@@ -84,18 +86,20 @@ impl CachedEnvironment {
         // Search in the content-addressed cache.
         let cache_entry = cache.entry(CacheBucket::Environments, interpreter_hash, resolution_hash);
 
-        // Lock the interpreter, to avoid concurrent modification across processes.
+        // Lock at the interpreter level, to avoid concurrent modification across processes.
         fs_err::tokio::create_dir_all(cache_entry.dir()).await?;
         let _lock = LockedFile::acquire(
             cache_entry.dir().join(".lock"),
             cache_entry.dir().user_display(),
         )?;
 
-        // If the receipt exists, return the environment.
         let ok = cache_entry.path().join(".ok");
+
+        if settings.reinstall.is_none() {
+            // If the receipt exists, return the environment.
             if ok.is_file() {
                 debug!(
-                "Found existing cached environment at: `{}`",
+                    "Reusing cached environment at: `{}`",
                     cache_entry.path().display()
                 );
                 return Ok(Self(PythonEnvironment::from_root(
@@ -103,6 +107,19 @@ impl CachedEnvironment {
                     cache,
                 )?));
             }
+        } else {
+            // If the receipt exists, remove it.
+            match fs_err::tokio::remove_file(&ok).await {
+                Ok(()) => {
+                    debug!(
+                        "Removed receipt for environment at: `{}`",
+                        cache_entry.path().display()
+                    );
+                }
+                Err(err) if err.kind() == std::io::ErrorKind::NotFound => {}
+                Err(err) => return Err(err.into()),
+            }
+        }
 
         debug!(
             "Creating cached environment at: `{}`",
@@ -117,8 +134,6 @@ impl CachedEnvironment {
             false,
         )?;
 
-        // TODO(charlie): Rather than passing all the arguments to `sync_environment`, return a
-        // struct that lets us "continue" from `resolve_environment`.
         let venv = sync_environment(
             venv,
             &resolution,

crates/uv/tests/tool_run.rs

@@ -508,6 +508,63 @@ fn tool_run_cache() {
     Resolved [N] packages in [TIME]
     "###);
 
+    // Verify that `--reinstall` reinstalls everything.
+    uv_snapshot!(context.filters(), context.tool_run()
+        .arg("-p")
+        .arg("3.12")
+        .arg("--reinstall")
+        .arg("black")
+        .arg("--version")
+        .env("UV_TOOL_DIR", tool_dir.as_os_str())
+        .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    black, 24.3.0 (compiled: yes)
+    Python (CPython) 3.12.[X]
+
+    ----- stderr -----
+    warning: `uv tool run` is experimental and may change without warning
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + black==24.3.0
+     + click==8.1.7
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+    "###);
+
+    // Verify that `--reinstall-package` reinstalls everything. We may want to change this.
+    uv_snapshot!(context.filters(), context.tool_run()
+        .arg("-p")
+        .arg("3.12")
+        .arg("--reinstall-package")
+        .arg("packaging")
+        .arg("black")
+        .arg("--version")
+        .env("UV_TOOL_DIR", tool_dir.as_os_str())
+        .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    black, 24.3.0 (compiled: yes)
+    Python (CPython) 3.12.[X]
+
+    ----- stderr -----
+    warning: `uv tool run` is experimental and may change without warning
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + black==24.3.0
+     + click==8.1.7
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+    "###);
+
     // Verify that varying the interpreter leads to a fresh environment.
     uv_snapshot!(context.filters(), context.tool_run()
         .arg("-p")