What causes "resource command produced no output" in jdx/mise?

Run the command manually and confirm it prints non-empty output to stdout.

resource command produced no output

Error message

resource command produced no output

What it means

run_resource_command runs the tool's command in isolation (null stdin/stderr, timeout, 4MB read cap) and returns its stdout. If the captured output trims to empty, it bails, because consumers (like completion script derivation) require non-empty output. This treats silent commands as failures since there is nothing to use downstream.

Source

Thrown at src/packslip.rs:1090

    path: &Path,
    args: &[String],
    env: &BTreeMap<String, String>,
    install_path: &Path,
    timeout: std::time::Duration,
) -> Result<String> {
    let work = tempfile::tempdir()?;
    let output = CmdLineRunner::new(path)
        .args(args)
        .envs(env)
        .prepend_path(vec![install_path.join(MISE_BINS_DIR)])?
        .current_dir(work.path())
        .stdin(std::process::Stdio::null())
        .stderr(std::process::Stdio::null())
        .with_timeout(timeout)
        .read_isolated(4 * 1024 * 1024)
        .await?;
    if output.trim().is_empty() {
        bail!("resource command produced no output");
    }
    Ok(output)
}

/// Derive a completion script from a CLI spec with the consumer's own
/// tooling. Only the `usage` format is known.
fn derive_from_spec(format: &str, bin: &str, spec: &Path, shell: &str) -> Result<String> {
    if format != "usage" {
        bail!("mise cannot derive completions from a {format} spec");
    }
    // Validate before returning a loader, so an invalid preferred spec still
    // falls through to another resource source.
    file::read_to_string(spec)?
        .parse::<usage::Spec>()
        .map_err(|err| eyre!("invalid usage specification: {err}"))?;
    let shell = usage_rs::complete::Shell::from_name(shell)
        .ok_or_else(|| eyre!("unsupported completion shell: {shell}"))?;
    let path = completions::encode_spec_path(spec);

View on GitHub (pinned to afd2eddd3a)

Solutions

Run the command manually and confirm it prints non-empty output to stdout.
Fix the exec entry to use the correct command/flags that emit stdout (e.g. correct completion subcommand).
Ensure the command doesn't depend on stdin or a TTY (stdin is nulled and stderr discarded in isolated execution).
If output is legitimately huge, reduce it or check it isn't being truncated by the 4MB read cap.

Example fix

# before: prints to stderr, stdout stays empty
exec = ["rg", "--completion"]

# after: correct subcommand that prints completions to stdout
exec = ["rg", "--generate", "complete", "--"], # or the tool's documented completion command

Defensive patterns

Strategy: validation

Validate before calling

let out = Command::new(&program).args(args)
    .stdin(Stdio::null()).stderr(Stdio::null()).output()?;
if out.stdout.iter().all(|&b| (b as char).is_whitespace()) {
    eprintln!("{program} prints nothing to stdout; resource commands require non-empty stdout");
}

Try / catch

match run_tool(config, &backend, &tv, &argv, &env).await {
    Err(e) if e.to_string().contains("produced no output") => {
        eprintln!("Run the command manually; ensure it writes completions to stdout (stderr is discarded)");
    }
    Ok(out) => use(out),
    Err(e) => return Err(e),
}

Prevention

Confirm resource commands write to stdout, not stderr — stderr is nulled in isolated execution.
Avoid commands requiring TTY or stdin; isolated runs use null stdin.
Keep expected output well under the 4MB read cap.
Test each manifest exec entry by running it manually before shipping.

When it happens

Trigger: An exec/resource command that writes nothing to stdout — e.g. a completion command that prints to stderr, a command whose output exceeded the 4MB read cap leaving nothing usable, or a command that failed silently — invoked via run_tool or fetch_files resource commands.

Common situations: Wrong completion flag for the tool (e.g. a flag that prints usage to stderr); command expects a TTY and prints nothing when stdin is null; the tool's completion subcommand was renamed so the command exits without stdout; output was empty because the tool requires an argument.

Related errors

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/7f016e8d6c288fad. Report an issue: GitHub.