astral-sh/ruff · error

Failed to create virtual environment: {}

Error message

Failed to create virtual environment: {}

What it means

The benchmark harness creates the cached virtual environment with `uv venv --python <version> --allow-existing` under target/benchmark_cache/<name>/.venv; a nonzero exit raises this error including uv's stderr.

Source

Thrown at crates/ruff_benchmark/src/real_world_projects.rs:287

        .arg("--version")
        .output()
        .context("Failed to execute uv version check.")?;

    if !uv_check.status.success() {
        anyhow::bail!(
            "uv is not installed or not found in PATH. If you need to install it, follow the instructions at https://docs.astral.sh/uv/getting-started/installation/"
        );
    }

    let python_version_str = python_version.to_string();

    let output = Command::new("uv")
        .args(["venv", "--python", &python_version_str, "--allow-existing"])
        .arg(venv_path)
        .output()
        .context("Failed to execute uv venv command")?;

    anyhow::ensure!(
        output.status.success(),
        "Failed to create virtual environment: {}",
        String::from_utf8_lossy(&output.stderr)
    );

    if dependencies.is_empty() {
        tracing::debug!("No dependencies to install for project '{}'", name);
        return Ok(());
    }

    // Install dependencies with date constraint in the isolated environment
    let mut cmd = Command::new("uv");
    cmd.args([
        "pip",
        "install",
        "--python",
        venv_path.to_str().unwrap(),
        "--exclude-newer",

View on GitHub (pinned to 672bb4edf0)

Solutions

1. Read the embedded stderr — it names the missing interpreter or underlying error
2. Pre-install the required Python version (`uv python install <version>`) or allow network access so uv can download it
3. Remove a stale or broken environment: delete target/benchmark_cache/<name>/.venv and rerun

Example fix

# before
 bench run fails: Failed to create virtual environment: error: no interpreter found ...

# after
uv python install 3.12 && cargo bench --bench <real-world-bench>

uv python list 2>/dev/null | grep -q "$python_version" || uv python install "$python_version"
cargo bench --bench "$bench"

for i in 1 2; do
  cargo bench --bench "$bench" && break
  echo "venv setup attempt $i failed; clearing venv" >&2
  rm -rf "target/benchmark_cache/$project/.venv"
done

When it happens

Trigger: The pinned Python version is neither installed locally nor downloadable (offline machine, blocked python-build-standalone download), or the venv path has permission/stale-state problems.

Common situations: Air-gapped CI where uv cannot fetch interpreters; system lacking the pinned Python major.minor; leftover root-owned .venv from an earlier privileged run.

Related errors

• Could not determine source kind for file: {}
• Could not determine source kind for file: {}
• Git fetch of commit {} failed: {}
• Git checkout of commit {} failed: {}
• Git clone failed: {}

AI-assisted analysis of astral-sh/ruff@672bb4edf0 (2026-08-16). Data as JSON: /api/errors/589570dfb29342eb. Report an issue: GitHub.