LykosAI/StabilityMatrix · error · ProcessException

pip show returned no output for package

Error message

pip show returned no output for package '{packageName}': {result.StandardError}

What it means

PipShow throws ProcessException when pip exits 0 but its stdout is empty/whitespace. Since `pip show` on success always prints package metadata, empty output means an unexpected state (e.g. stderr had warnings only, or output was swallowed). The message carries the StandardError for diagnosis.

Solutions

Inspect the StandardError in the message for clues from the pip process.
Re-run `venv/bin/python -m pip show <pkg>` manually to see whether output is produced.
Check that no wrapper script/alias overrides pip within the venv.
Retry after reinstalling the package or updating pip in the venv.

Example fix

// before
var result = venv.PipShow("requests").Packages[0];
// after
try { var result = venv.PipShow("requests").Packages[0]; }
catch (ProcessException ex) { Logger.Warn(ex, "pip show empty output"); return null; }

Defensive patterns

Strategy: try-catch

Validate before calling

var listed = await venv.PipList();
bool exists = listed.Any(p => p.PackageName == packageName);

Try / catch

try { return venv.PipShow(pkg); }
catch (ProcessException ex) { Logger.Warn(ex, "pip show empty output for {Pkg}", pkg); return null; }

Prevention

Validate output non-empty before calling Parse in your own wrappers
Avoid pip wrappers/shims that suppress stdout
Retry once on empty output before surfacing the error

When it happens

Trigger: PipShow(packageName) returns exit code 0 but result.StandardOutput is null/empty; PipShowResult.Parse would otherwise fail.

Common situations: Pip stdout redirected or truncated by an environment; a shimmed/wrapped pip that prints nothing; locale/encoding problems; unusual pip forks emitting to stderr.

Related errors

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/4e56d34bb2bb8fd8. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Core/Python/PyVenvRunner.cs:384

            || result.StandardError?.Contains("Package(s) not found", StringComparison.OrdinalIgnoreCase)
                == true;

        if (packageNotFound)
        {
            return null;
        }

        // Check return code
        if (result.ExitCode != 0)
        {
            throw new ProcessException(
                $"pip show failed with code {result.ExitCode}: {result.StandardOutput}, {result.StandardError}"
            );
        }

        if (string.IsNullOrWhiteSpace(result.StandardOutput))
        {
            throw new ProcessException(
                $"pip show returned no output for package '{packageName}': {result.StandardError}"
            );
        }

        return PipShowResult.Parse(result.StandardOutput);
    }

    /// <summary>
    /// Run a pip index command, return result as PipIndexResult.
    /// </summary>
    public async Task<PipIndexResult?> PipIndex(
        string packageName,
        string? indexUrl = null,
        bool includePrerelease = false
    )
    {
        if (!File.Exists(PipPath))
        {

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