Update activation scripts from virtualenv (#3376)

## Summary

Refreshes some of the activation scripts, and fixes some bugs in
`activate_this.py` that were likely the rest of some erroneous
copy-pasting.

Closes https://github.com/astral-sh/uv/issues/3346.

## Test Plan

```
❯ python
Python 3.12.0 (main, Feb 28 2024, 09:44:16) [Clang 15.0.0 (clang-1500.1.0.2.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import httpx
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'httpx'
>>> activator = '.venv/bin/activate_this.py'
>>> with open(activator) as f:
...     exec(f.read(), {'__file__': activator})
...
>>> import httpx
```

Cargo.lock

@@ -5067,6 +5067,7 @@ dependencies = [
  "clap",
  "directories",
  "fs-err",
+ "itertools 0.12.1",
  "pathdiff",
  "platform-tags",
  "pypi-types",

crates/uv-virtualenv/Cargo.toml

@@ -32,6 +32,7 @@ anstream = { workspace = true }
 clap = { workspace = true, features = ["derive"], optional = true }
 directories = { workspace = true }
 fs-err = { workspace = true }
+itertools = { workspace = true }
 pathdiff = { workspace = true }
 thiserror = { workspace = true }
 tracing = { workspace = true }

crates/uv-virtualenv/src/activator/activate.fish

@@ -83,7 +83,7 @@ set -gx VIRTUAL_ENV '{{ VIRTUAL_ENV_DIR }}'
 
 # https://github.com/fish-shell/fish-shell/issues/436 altered PATH handling
 if test (echo $FISH_VERSION | head -c 1) -lt 3
-   set -gx _OLD_VIRTUAL_PATH (_bashify_path $PATH)
+    set -gx _OLD_VIRTUAL_PATH (_bashify_path $PATH)
 else
     set -gx _OLD_VIRTUAL_PATH $PATH
 end

crates/uv-virtualenv/src/activator/activate.ps1

@@ -67,7 +67,7 @@ else {
 
 New-Variable -Scope global -Name _OLD_VIRTUAL_PATH -Value $env:PATH
 
-$env:PATH = "$env:VIRTUAL_ENV/{{ BIN_NAME }};" + $env:PATH
+$env:PATH = "$env:VIRTUAL_ENV/{{ BIN_NAME }}{{ PATH_SEP }}" + $env:PATH
 if (!$env:VIRTUAL_ENV_DISABLE_PROMPT) {
     function global:_old_virtual_prompt {
         ""

crates/uv-virtualenv/src/activator/activate_this.py

@@ -26,6 +26,7 @@ Use exec(open(this_file).read(), {'__file__': this_file}).
 
 This can be used when you must use an existing Python interpreter, not the virtualenv bin/python.
 """  # noqa: D415
+
 from __future__ import annotations
 
 import os
@@ -35,7 +36,7 @@ import sys
 try:
     abs_file = os.path.abspath(__file__)
 except NameError as exc:
-    msg = "You must use exec(open(this_file).read(), {'__file__': this_file}))"
+    msg = "You must use exec(open(this_file).read(), {'__file__': this_file})"
     raise AssertionError(msg) from exc
 
 bin_dir = os.path.dirname(abs_file)
@@ -44,13 +45,13 @@ base = bin_dir[: -len("{{ BIN_NAME }}") - 1]  # strip away the bin part from the
 # prepend bin to PATH (this file is inside the bin directory)
 os.environ["PATH"] = os.pathsep.join([bin_dir, *os.environ.get("PATH", "").split(os.pathsep)])
 os.environ["VIRTUAL_ENV"] = base  # virtual env is right above bin directory
-os.environ["VIRTUAL_ENV_PROMPT"] = "" or os.path.basename(base)  # noqa: SIM222
+os.environ["VIRTUAL_ENV_PROMPT"] = "{{ VIRTUAL_PROMPT }}" or os.path.basename(base)  # noqa: SIM222
 
 # add the virtual environments libraries to the host python import mechanism
 prev_length = len(sys.path)
 for lib in "{{ RELATIVE_SITE_PACKAGES }}".split(os.pathsep):
     path = os.path.realpath(os.path.join(bin_dir, lib))
-    site.addsitedir(path.decode("utf-8") if "" else path)
+    site.addsitedir(path)
 sys.path[:] = sys.path[prev_length:] + sys.path[0:prev_length]
 
 sys.real_prefix = sys.prefix

crates/uv-virtualenv/src/bare.rs

@@ -1,4 +1,4 @@
-//! Create a bare virtualenv without any packages install
+//! Create a bare virtualenv without any packages installed.
 
 use std::env;
 use std::env::consts::EXE_SUFFIX;
@@ -8,14 +8,16 @@ use std::path::Path;
 
 use fs_err as fs;
 use fs_err::File;
-use pypi_types::Scheme;
+use itertools::Itertools;
 use tracing::info;
 
-use crate::{Error, Prompt};
+use pypi_types::Scheme;
 use uv_fs::{cachedir, Simplified};
 use uv_interpreter::{Interpreter, VirtualEnvironment};
 use uv_version::version;
 
+use crate::{Error, Prompt};
+
 /// The bash activate scripts with the venv dependent paths patches out
 const ACTIVATE_TEMPLATES: &[(&str, &str)] = &[
     ("activate", include_str!("activator/activate")),
@@ -195,11 +197,21 @@ pub fn create_bare_venv(
 
     // Add all the activate scripts for different shells
     for (name, template) in ACTIVATE_TEMPLATES {
-        let relative_site_packages = pathdiff::diff_paths(
-            &interpreter.virtualenv().purelib,
-            &interpreter.virtualenv().scripts,
-        )
-        .expect("Failed to calculate relative path to site-packages");
+        let path_sep = if cfg!(windows) { ";" } else { ":" };
+
+        let relative_site_packages = [
+            interpreter.virtualenv().purelib.as_path(),
+            interpreter.virtualenv().platlib.as_path(),
+        ]
+        .iter()
+        .dedup()
+        .map(|path| {
+            pathdiff::diff_paths(path, &interpreter.virtualenv().scripts)
+                .expect("Failed to calculate relative path to site-packages")
+        })
+        .map(|path| path.simplified().to_str().unwrap().replace('\\', "\\\\"))
+        .join(path_sep);
+
         let activator = template
             .replace(
                 "{{ VIRTUAL_ENV_DIR }}",
@@ -211,10 +223,8 @@ pub fn create_bare_venv(
                 "{{ VIRTUAL_PROMPT }}",
                 prompt.as_deref().unwrap_or_default(),
             )
-            .replace(
-                "{{ RELATIVE_SITE_PACKAGES }}",
-                relative_site_packages.simplified().to_str().unwrap(),
-            );
+            .replace("{{ PATH_SEP }}", path_sep)
+            .replace("{{ RELATIVE_SITE_PACKAGES }}", &relative_site_packages);
         fs::write(scripts.join(name), activator)?;
     }