Add parameter support to failed block for capturing exit codes

[Copilot]

Overview

This PR implements the ability to pass failure exit codes to failed blocks via parameters, matching the existing functionality of then blocks. This addresses issue #XXX.

Problem

Previously, when handling failures in Amber, developers had to manually capture the exit code in a temporary variable before running any additional commands in the failed block:

$ command $ failed {
    let error = status
    trust $ cleanup_command $
    echo "Exit code: {error}"
}

This was necessary because running additional commands inside the failed block would overwrite the status variable, losing the original error code.

Solution

The failed block now supports an optional parameter syntax, similar to the then block:

$ command $ failed(error) {
    trust $ cleanup_command $
    echo "Exit code: {error}"
}

The parameter captures the exit code immediately and keeps it isolated from subsequent command executions.

Implementation Details

• Modified: src/modules/condition/failed.rs

  • Added param_name and param_global_id fields to the Failed struct
  • Enhanced parser to handle optional (parameter_name) syntax
  • Updated translator to assign exit code to parameter variable when provided
  • Added validation for empty parameter names

• Backward Compatibility: All existing code without parameters continues to work exactly as before

• Test Coverage: Added 3 new test cases

  • Basic parameter functionality
  • Parameter isolation verification
  • Error handling for invalid syntax

Examples

Basic usage

silent $ nonexistent_command $ failed(code) {
    echo "Command failed with exit code: {code}"
}

Parameter isolation

silent $ false $ failed(error) {
    trust $ ls > /dev/null $  // This changes 'status'
    echo "Original error: {error}"  // But parameter preserves original code
    echo "Current status: {status}"
}

Testing

• ✅ All 364 tests pass
• ✅ Generated Bash code verified for correctness
• ✅ Backward compatibility confirmed
• ✅ Consistent with then block behavior

Benefits

• Cleaner code: Eliminates need for temporary variables
• Explicit intent: Parameter makes error handling more readable
• Preserves context: Original exit code remains accessible regardless of subsequent operations
• API consistency: Matches the existing then block pattern

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Feature] Ability to pass failure exit code to the failed block</issue_title>
<issue_description>Is your feature request related to a problem? Please describe.
Currently we have failed block that runs when a failure has to be handled. We already expose then block which exposes error code under a variable.

$ ... $ then(exit_code) {
  echo exit_code
}

Add ability to do the same for failure block.

Describe the solution you'd like
Ability to run this block of code like this

$ ... $ failed(code) {
  echo code
}

Additional context
This is important because in the handling block we may run multiple other failing expression, thus introducing a necessity to create a failed variable.

// Before
$ ... $ failed {
  let error = status
  trust $ ... $
  echo "Exit code: {error}"
}

// After
$ ... $ failed(error) {
  trust $ ... $
  echo "Exit code: {error}"
}

</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #801

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