PR Summary

Fix Set-PSDebug -Trace to display all lines of multiline commands.

PR Context

Fixes #8113

When using Set-PSDebug -Trace 1 or -Trace 2, multiline commands (e.g., using backtick line continuation) only showed the first line in debug output. This made it difficult to trace and debug scripts with multiline commands.

Before this fix:

Set-PSDebug -Trace 1

Write-Output "foo `
bar"

Output:

DEBUG:    3+  >>>> Write-Output "foo `

foo
bar

After this fix:

Output:

DEBUG:    3+  >>>> Write-Output "foo `
DEBUG:    4+  >>>> bar"
foo
bar

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge. If this PR is a work in progress, please open this as a Draft Pull Request and mark it as Ready to Review when it is ready to merge.
• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
    • Experimental feature name(s):
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed:
• Testing - New and feature
  • N/A or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed

Description

Root Cause

The TraceLine method in the debugger was calling PositionUtilities.BriefMessage(extent.StartScriptPosition), which only considers the start position of an extent. For multiline commands, this meant only the first line was displayed.

Solution

1. Added a new overload PositionUtilities.BriefMessage(IScriptExtent extent) that handles multiline extents by:

   • Detecting if an extent spans multiple lines
   • For single-line extents, delegating to the existing method
   • For multiline extents, formatting each line with appropriate line numbers and markers

2. Changed TraceLine to call the new extent-based overload and write each line separately so each gets the DEBUG: prefix.

Files Changed

• src/System.Management.Automation/engine/debugger/debugger.cs - Changed TraceLine to use extent-based BriefMessage and write each line separately
• src/System.Management.Automation/engine/parser/Position.cs - Added new BriefMessage(IScriptExtent) overload
• test/powershell/Modules/Microsoft.PowerShell.Core/Set-PSDebug.Tests.ps1 - Added tests for multiline command tracing with -Trace 1 and -Trace 2

Testing

Test Coverage

Added test cases that:

1. Create a script with a multiline command using backtick line continuation
2. Run it in a separate process to capture trace output
3. Verify both the first line (Write-Output) and continuation line (bar") appear in debug output with DEBUG: prefix

Tests cover both -Trace 1 and -Trace 2 options.

Automated Tests

All tests pass:

Context Tracing can be used
  [+] Should be able to go through the tracing options
  [+] Should be able to set strict
  [+] Should skip magic extents created by pwsh
  [+] Should trace all lines of a multiline command
  [+] Should trace all lines of a multiline command with -Trace 2

Tests Passed: 5, Failed: 0