VIRTUAL_ENV takes precedence over CONDA_PREFIX (#2574)

It is a common pattern to have an active conda base env (that sets
`CONDA_PREFIX`) and then create a venv on top of that (setting
`VIRTUAL_ENV`).

Previously, we would error when both `VIRTUAL_ENV` and `CONDA_PREFIX`
were set, now `VIRTUAL_ENV` takes precedence over `CONDA_PREFIX`.

Fixes #2028

crates/uv-interpreter/src/lib.rs

@@ -33,8 +33,6 @@ mod virtualenv;
 pub enum Error {
     #[error("Expected `{0}` to be a virtualenv, but `pyvenv.cfg` is missing")]
     MissingPyVenvCfg(PathBuf),
-    #[error("Both VIRTUAL_ENV and CONDA_PREFIX are set. Please unset one of them.")]
-    Conflict,
     #[error("No versions of Python could be found. Is Python installed?")]
     PythonNotFound,
     #[error("Failed to locate a virtualenv or Conda environment (checked: `VIRTUAL_ENV`, `CONDA_PREFIX`, and `.venv`). Run `uv venv` to create a virtualenv.")]

crates/uv-interpreter/src/python_environment.rs

@@ -1,7 +1,7 @@
 use std::env;
 use std::path::{Path, PathBuf};
 
-use tracing::debug;
+use tracing::{debug, info};
 
 use uv_cache::Cache;
 use uv_fs::{LockedFile, Simplified};
@@ -124,32 +124,20 @@ impl PythonEnvironment {
 
 /// Locate the current virtual environment.
 pub(crate) fn detect_virtual_env() -> Result<Option<PathBuf>, Error> {
-    match (
-        env::var_os("VIRTUAL_ENV").filter(|value| !value.is_empty()),
-        env::var_os("CONDA_PREFIX").filter(|value| !value.is_empty()),
-    ) {
-        (Some(dir), None) => {
-            debug!(
-                "Found a virtualenv through VIRTUAL_ENV at: {}",
-                Path::new(&dir).display()
-            );
-            return Ok(Some(PathBuf::from(dir)));
-        }
-        (None, Some(dir)) => {
-            debug!(
-                "Found a virtualenv through CONDA_PREFIX at: {}",
-                Path::new(&dir).display()
-            );
-            return Ok(Some(PathBuf::from(dir)));
-        }
-        (Some(venv), Some(conda)) if venv == conda => return Ok(Some(PathBuf::from(venv))),
-        (Some(_), Some(_)) => {
-            return Err(Error::Conflict);
-        }
-        (None, None) => {
-            // No environment variables set. Try to find a virtualenv in the current directory.
-        }
-    };
+    if let Some(dir) = env::var_os("VIRTUAL_ENV").filter(|value| !value.is_empty()) {
+        info!(
+            "Found a virtualenv through VIRTUAL_ENV at: {}",
+            Path::new(&dir).display()
+        );
+        return Ok(Some(PathBuf::from(dir)));
+    }
+    if let Some(dir) = env::var_os("CONDA_PREFIX").filter(|value| !value.is_empty()) {
+        info!(
+            "Found a virtualenv through CONDA_PREFIX at: {}",
+            Path::new(&dir).display()
+        );
+        return Ok(Some(PathBuf::from(dir)));
+    }
 
     // Search for a `.venv` directory in the current or any parent directory.
     let current_dir = env::current_dir().expect("Failed to detect current directory");