Dax Issue #300 Reproduction

This directory contains minimal reproduction cases for dax issue #300: "Execution error that may be due to missing tty or streams for Multiple layers of Dax+Jupyter Notebooks"

The Problem

When dax is used to execute a process (like Jupyter) that runs code containing dax commands, the nested dax execution fails with:

Error: Exited with code: 128
    at CommandChild.pipedStdoutBuffer

Root Cause

Dax defaults to using "inherit" for stdout/stderr streams. In nested execution contexts (especially non-interactive environments like Jupyter notebooks), stdio inheritance fails because the parent process's streams aren't properly available or configured.

Key locations in dax source:

• Default stdio config: src/command.ts:138-143
• Error thrown: src/command.ts:783
• Stdio mapping: src/commands/executable.ts:126-134

Reproduction Scripts

1. Minimal Reproduction (No Jupyter Required)

The simplest way to test nested dax execution:

deno run --allow-all minimal_repro.ts

This script:

• Creates an inner script that uses dax
• Attempts to run it using outer dax with different stdio configurations
• Tests failure scenarios with default stdio inheritance
• Shows it works with explicit piped stdio

Note: This minimal reproduction actually succeeds in all scenarios when run in a normal terminal environment. The issue appears to be specific to Jupyter's non-interactive environment where stdio streams are handled differently.

2. Jupyter Notebook Reproduction (Requires Jupyter)

Full reproduction matching the original issue report:

Setup:

# Install Jupyter
pip install jupyter

# Install Deno Jupyter kernel
deno jupyter --install

Run:

# Execute the test harness
deno run --allow-all run_notebook.ts

This demonstrates the full nested scenario:

1. Outer dax (in run_notebook.ts)
2. Executes Jupyter nbconvert
3. Which runs notebook_with_dax.ipynb
4. Which contains dax commands (inner dax)

3. Simple Dax Command

A basic script using dax that works fine on its own:

deno run --allow-all simple_dax_command.ts

This succeeds because there's no nested execution.

Expected vs Actual Behavior

Expected

All scenarios should execute successfully, with dax commands working in any context.

Actual

• ✓ Simple dax command works
• ✗ Nested dax execution fails with exit code 128
• ✓ Using explicit .stdout("piped").stderr("piped") works
• ✓ Using native Deno.Command instead of dax works

Workaround

Until this is fixed, you can work around the issue by explicitly piping stdio:

// Instead of:
await $`command`;

// Use:
await $`command`.stdout("piped").stderr("piped");

Proposed Fix

The issue can be fixed by detecting non-interactive/Jupyter environments and automatically using piped stdio instead of inherited stdio. See analysis in the issue comments for detailed implementation options.

Files

• minimal_repro.ts - Simplest reproduction without Jupyter
• run_notebook.ts - Full Jupyter notebook execution scenario
• notebook_with_dax.ipynb - Jupyter notebook using dax
• simple_dax_command.ts - Basic dax script (works fine)
• README.md - This file

Testing the Fix

Once a fix is implemented, run all reproduction scripts to verify:

1. Nested dax execution works in all scenarios
2. Default behavior unchanged for normal (non-nested) execution
3. Jupyter notebook execution succeeds
4. No regressions in existing functionality