Revert "Includes sys.prefix in cached environment keys to avoid --with collisions across projects (#14403)"

This reverts commit ec54dce919.

crates/uv-python/src/environment.rs

@@ -174,7 +174,7 @@ impl PythonEnvironment {
     /// N.B. This function also works for system Python environments and users depend on this.
     pub fn from_root(root: impl AsRef<Path>, cache: &Cache) -> Result<Self, Error> {
         debug!(
-            "Checking for Python environment at: {}",
+            "Checking for Python environment at: `{}`",
             root.as_ref().user_display()
         );
         match root.as_ref().try_exists() {

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

@@ -107,15 +107,13 @@ impl CachedEnvironment {
         printer: Printer,
         preview: PreviewMode,
     ) -> Result<Self, ProjectError> {
-        // Resolve the "base" interpreter, which resolves to an underlying parent interpreter if the
-        // given interpreter is a virtual environment.
-        let base_interpreter = Self::base_interpreter(interpreter, cache)?;
+        let interpreter = Self::base_interpreter(interpreter, cache)?;
 
         // Resolve the requirements with the interpreter.
         let resolution = Resolution::from(
             resolve_environment(
                 spec,
-                &base_interpreter,
+                &interpreter,
                 build_constraints.clone(),
                 &settings.resolver,
                 network_settings,
@@ -143,29 +141,20 @@ impl CachedEnvironment {
         // Use the canonicalized base interpreter path since that's the interpreter we performed the
         // resolution with and the interpreter the environment will be created with.
         //
-        // We also include the canonicalized `sys.prefix` of the non-base interpreter, that is, the
-        // virtual environment's path. Originally, we shared cached environments independent of the
-        // environment they'd be layered on top of. However, this causes collisions as the overlay
-        // `.pth` file can be overridden by another instance of uv. Including this element in the key
-        // avoids this problem at the cost of creating separate cached environments for identical
-        // `--with` invocations across projects. We use `sys.prefix` rather than `sys.executable` so
-        // we can canonicalize it without invalidating the purpose of the element — it'd probably be
-        // safe to just use the absolute `sys.executable` as well.
-        //
-        // TODO(zanieb): Since we're not sharing these environmments across projects, we should move
-        // [`CachedEvnvironment::set_overlay`] etc. here since the values there should be constant
-        // now.
+        // We cache environments independent of the environment they'd be layered on top of. The
+        // assumption is such that the environment will _not_ be modified by the user or uv;
+        // otherwise, we risk cache poisoning. For example, if we were to write a `.pth` file to
+        // the cached environment, it would be shared across all projects that use the same
+        // interpreter and the same cached dependencies.
         //
         // TODO(zanieb): We should include the version of the base interpreter in the hash, so if
         // the interpreter at the canonicalized path changes versions we construct a new
         // environment.
-        let environment_hash = cache_digest(&(
-            &canonicalize_executable(base_interpreter.sys_executable())?,
-            &interpreter.sys_prefix().canonicalize()?,
-        ));
+        let interpreter_hash =
+            cache_digest(&canonicalize_executable(interpreter.sys_executable())?);
 
         // Search in the content-addressed cache.
-        let cache_entry = cache.entry(CacheBucket::Environments, environment_hash, resolution_hash);
+        let cache_entry = cache.entry(CacheBucket::Environments, interpreter_hash, resolution_hash);
 
         if cache.refresh().is_none() {
             if let Ok(root) = cache.resolve_link(cache_entry.path()) {
@@ -179,7 +168,7 @@ impl CachedEnvironment {
         let temp_dir = cache.venv_dir()?;
         let venv = uv_virtualenv::create_venv(
             temp_dir.path(),
-            base_interpreter,
+            interpreter,
             uv_virtualenv::Prompt::None,
             false,
             false,

crates/uv/tests/it/run.rs

@@ -1302,7 +1302,6 @@ fn run_with_pyvenv_cfg_file() -> Result<()> {
     uv = [UV_VERSION]
     version_info = 3.12.[X]
     include-system-site-packages = false
-    relocatable = true
     extends-environment = [PARENT_VENV]
 
 
@@ -4778,7 +4777,6 @@ fn run_groups_include_requires_python() -> Result<()> {
         baz = ["iniconfig"]
         dev = ["sniffio", {include-group = "foo"}, {include-group = "baz"}]
 
-
         [tool.uv.dependency-groups]
         foo = {requires-python="<3.13"}
         bar = {requires-python=">=3.13"}
@@ -4923,8 +4921,8 @@ fn run_repeated() -> Result<()> {
     Resolved 1 package in [TIME]
     "###);
 
-    // Re-running as a tool does require reinstalling `typing-extensions`, since the base venv is
-    // different.
+    // Re-running as a tool doesn't require reinstalling `typing-extensions`, since the environment
+    // is cached.
     uv_snapshot!(
         context.filters(),
         context.tool_run().arg("--with").arg("typing-extensions").arg("python").arg("-c").arg("import typing_extensions; import iniconfig"), @r#"
@@ -4934,8 +4932,6 @@ fn run_repeated() -> Result<()> {
 
     ----- stderr -----
     Resolved 1 package in [TIME]
-    Installed 1 package in [TIME]
-     + typing-extensions==4.10.0
     Traceback (most recent call last):
       File "<string>", line 1, in <module>
         import typing_extensions; import iniconfig
@@ -4982,8 +4978,7 @@ fn run_without_overlay() -> Result<()> {
      + typing-extensions==4.10.0
     "###);
 
-    // Import `iniconfig` in the context of a `tool run` command, which should fail. Note that
-    // typing-extensions gets installed again, because the venv is not shared.
+    // Import `iniconfig` in the context of a `tool run` command, which should fail.
     uv_snapshot!(
         context.filters(),
         context.tool_run().arg("--with").arg("typing-extensions").arg("python").arg("-c").arg("import typing_extensions; import iniconfig"), @r#"
@@ -4993,8 +4988,6 @@ fn run_without_overlay() -> Result<()> {
 
     ----- stderr -----
     Resolved 1 package in [TIME]
-    Installed 1 package in [TIME]
-     + typing-extensions==4.10.0
     Traceback (most recent call last):
       File "<string>", line 1, in <module>
         import typing_extensions; import iniconfig