PR Summary

Make -NoTypeInformation a pure no-op obsolete parameter and evaluate -IncludeTypeInformation by its value in Export-Csv and ConvertTo-Csv.

Fixes #26569

PR Context

Problem

When specifying both -IncludeTypeInformation:$false and -NoTypeInformation:$false, PowerShell throws an error even though both switches are explicitly set to $false:

'test' | Export-Csv -Path test.csv -IncludeTypeInformation:$false -NoTypeInformation:$false
# Error: Cannot specify both -IncludeTypeInformation and -NoTypeInformation.

This is because the code checked whether the parameters were provided, not their actual values.

Solution

Per WG-Cmdlets discussion:

1. -IncludeTypeInformation now respects its actual value (not just presence)
2. -NoTypeInformation is marked obsolete and treated as a pure no-op for backward compatibility
3. No code checks the value of -NoTypeInformation - it simply triggers a deprecation warning

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
  • Specifying both -IncludeTypeInformation and -NoTypeInformation no longer throws an error
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed: Document -NoTypeInformation parameter as obsolete for Export-Csv and ConvertTo-Csv MicrosoftDocs/PowerShell-Docs#12691
• Testing - New and feature
  • N/A - Removed obsolete test that expected mutual exclusion error
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed

Changes Made

1. CsvCommands.cs (-16/+6 lines)

• Added [Obsolete] attribute to -NoTypeInformation parameter
• Removed mutual exclusion check for -IncludeTypeInformation and -NoTypeInformation
• Removed NoTypeInformation value adjustment logic
• Changed type information output condition from if (NoTypeInformation == false) to if (IncludeTypeInformation)
• Updated XML documentation for both parameters

2. Export-Csv.Tests.ps1 (-5 lines)

• Removed test expecting mutual exclusion error

3. ConvertTo-Csv.Tests.ps1 (-5 lines)

• Removed test expecting mutual exclusion error

Total: 3 files changed, 6 insertions(+), 26 deletions(-)

Behavior Examples

Both switches with $false

'test' | Export-Csv -Path test.csv -IncludeTypeInformation:$false -NoTypeInformation:$false

-IncludeTypeInformation:$true

'test' | Export-Csv -Path test.csv -IncludeTypeInformation:$true
Get-Content test.csv | Select-Object -First 1

-IncludeTypeInformation:$false

'test' | Export-Csv -Path test.csv -IncludeTypeInformation:$false
Get-Content test.csv | Select-Object -First 1

-NoTypeInformation (obsolete)

'test' | Export-Csv -Path test.csv -NoTypeInformation

Testing

Test Results

Design Decision

The WG-Cmdlets comment mentioned moving -NoTypeInformation to a separate parameter set. However, since -NoTypeInformation is purely a no-op switch that has no effect on behavior, separating parameter sets would cause unnecessary errors when both parameters are specified together (even with $false values). Instead, this PR treats -NoTypeInformation as a truly ignored parameter that simply triggers a deprecation warning.