feat: allow passing extra config k,v pairs for pyvenv.cfg when creati…

…ng venv

crates/gourgeist/src/bare.rs

@@ -35,7 +35,7 @@ const VIRTUALENV_PATCH: &str = include_str!("_virtualenv.py");
 /// Very basic `.cfg` file format writer.
 fn write_cfg(
     f: &mut impl Write,
-    data: &[(&str, String); 8],
+    data: &[(String, String)],
     prompt: Option<String>,
 ) -> io::Result<()> {
     for (key, value) in data {
@@ -73,6 +73,7 @@ pub fn create_bare_venv(
     location: &Utf8Path,
     interpreter: &Interpreter,
     prompt: Prompt,
+    extra_cfg: Vec<(String, String)>,
 ) -> io::Result<VenvPaths> {
     // We have to canonicalize the interpreter path, otherwise the home is set to the venv dir instead of the real root.
     // This would make python-build-standalone fail with the encodings module not being found because its home is wrong.
@@ -226,31 +227,68 @@ pub fn create_bare_venv(
     } else {
         unimplemented!("Only Windows and Unix are supported")
     };
-    let pyvenv_cfg_data = &[
-        ("home", python_home),
-        (
-            "implementation",
-            interpreter.markers().platform_python_implementation.clone(),
-        ),
-        (
-            "version_info",
-            interpreter.markers().python_version.string.clone(),
-        ),
-        ("gourgeist", env!("CARGO_PKG_VERSION").to_string()),
-        // I wouldn't allow this option anyway
-        ("include-system-site-packages", "false".to_string()),
-        (
-            "base-prefix",
-            interpreter.base_prefix().to_string_lossy().to_string(),
-        ),
-        (
-            "base-exec-prefix",
-            interpreter.base_exec_prefix().to_string_lossy().to_string(),
-        ),
-        ("base-executable", base_python.to_string()),
+
+    // Validate extra_cfg
+    let reserved_keys = [
+        "home",
+        "implementation",
+        "version_info",
+        "gourgeist",
+        "include-system-site-packages",
+        "base-prefix",
+        "base-exec-prefix",
+        "base-executable",
+        "prompt",
     ];
+    for (key, _) in &extra_cfg {
+        if reserved_keys.contains(&key.as_str()) {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                format!("Reserved key found in extra_cfg: {key}"),
+            ));
+        }
+    }
+
+    let pyvenv_cfg_data: Vec<(String, String)> = [
+        vec![
+            ("home".to_string(), python_home),
+            (
+                "implementation".to_string(),
+                interpreter.markers().platform_python_implementation.clone(),
+            ),
+            (
+                "version_info".to_string(),
+                interpreter.markers().python_version.string.clone(),
+            ),
+            (
+                "gourgeist".to_string(),
+                env!("CARGO_PKG_VERSION").to_string(),
+            ),
+        ],
+        // Put custom cfg pairs after "gourgeist"
+        extra_cfg,
+        vec![
+            (
+                "include-system-site-packages".to_string(),
+                "false".to_string(),
+            ),
+            (
+                "base-prefix".to_string(),
+                interpreter.base_prefix().to_string_lossy().to_string(),
+            ),
+            (
+                "base-exec-prefix".to_string(),
+                interpreter.base_exec_prefix().to_string_lossy().to_string(),
+            ),
+            ("base-executable".to_string(), base_python.to_string()),
+        ],
+    ]
+    .into_iter()
+    .flatten()
+    .collect();
+
     let mut pyvenv_cfg = BufWriter::new(File::create(location.join("pyvenv.cfg"))?);
-    write_cfg(&mut pyvenv_cfg, pyvenv_cfg_data, prompt)?;
+    write_cfg(&mut pyvenv_cfg, &pyvenv_cfg_data, prompt)?;
     drop(pyvenv_cfg);
 
     let site_packages = if cfg!(unix) {

crates/gourgeist/src/lib.rs

@@ -51,11 +51,12 @@ pub fn create_venv(
     location: &Path,
     interpreter: Interpreter,
     prompt: Prompt,
+    extra_cfg: Vec<(String, String)>,
 ) -> Result<Virtualenv, Error> {
     let location: &Utf8Path = location
         .try_into()
         .map_err(|err: FromPathError| err.into_io_error())?;
-    let paths = create_bare_venv(location, &interpreter, prompt)?;
+    let paths = create_bare_venv(location, &interpreter, prompt, extra_cfg)?;
     Ok(Virtualenv::from_interpreter(
         interpreter,
         paths.root.as_std_path(),

crates/gourgeist/src/main.rs

@@ -36,7 +36,7 @@ fn run() -> Result<(), gourgeist::Error> {
         Cache::from_path(".gourgeist_cache")?
     };
     let info = Interpreter::query(python.as_std_path(), &platform, &cache).unwrap();
-    create_bare_venv(&location, &info, Prompt::from_args(cli.prompt))?;
+    create_bare_venv(&location, &info, Prompt::from_args(cli.prompt), Vec::new())?;
     Ok(())
 }
 

crates/uv-build/src/lib.rs

@@ -325,10 +325,17 @@ impl SourceBuild {
         let pep517_backend = Self::get_pep517_backend(setup_py, &source_tree, &default_backend)
             .map_err(|err| *err)?;
 
+        // Extra cfg for pyvenv.cfg to specify build backend
+        let extra_cfg = vec![(
+            "uv-build".to_string(),
+            env!("CARGO_PKG_VERSION").to_string(),
+        )];
+
         let venv = gourgeist::create_venv(
             &temp_dir.path().join(".venv"),
             interpreter.clone(),
             gourgeist::Prompt::None,
+            extra_cfg,
         )?;
 
         // Setup the build environment.

crates/uv/src/commands/venv.rs

@@ -119,8 +119,12 @@ async fn venv_impl(
     )
     .into_diagnostic()?;
 
+    // Extra cfg for pyvenv.cfg to specify uv version
+    let extra_cfg = vec![("uv".to_string(), env!("CARGO_PKG_VERSION").to_string())];
+
     // Create the virtual environment.
-    let venv = gourgeist::create_venv(path, interpreter, prompt).map_err(VenvError::Creation)?;
+    let venv = gourgeist::create_venv(path, interpreter, prompt, extra_cfg)
+        .map_err(VenvError::Creation)?;
 
     // Install seed packages.
     if seed {

crates/uv/tests/venv.rs

@@ -7,7 +7,9 @@ use assert_fs::prelude::*;
 
 use uv_fs::Normalized;
 
-use crate::common::{create_bin_with_executables, get_bin, uv_snapshot, EXCLUDE_NEWER};
+use crate::common::{
+    create_bin_with_executables, get_bin, uv_snapshot, TestContext, EXCLUDE_NEWER,
+};
 
 mod common;
 
@@ -575,3 +577,20 @@ fn virtualenv_compatibility() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn verify_pyvenv_cfg() {
+    let context = TestContext::new("3.12");
+    let venv = context.temp_dir.child(".venv");
+    let pyvenv_cfg = venv.child("pyvenv.cfg");
+
+    venv.assert(predicates::path::is_dir());
+
+    // Check pyvenv.cfg exists
+    pyvenv_cfg.assert(predicates::path::is_file());
+
+    // Check if "uv = version" is present in the file
+    let version = env!("CARGO_PKG_VERSION").to_string();
+    let search_string = format!("uv = {version}");
+    pyvenv_cfg.assert(predicates::str::contains(search_string));
+}