Invoke-RestMethod parameter combination of OutFile/PassThru does not write to file as intended

Problem description

In Invoke-RestMethod, the PassThru parameter must be used with the OutFile parameter. The intent is that you can write the results to the file and get the output to the pipeline. But the cmdlets only write to the pipeline, not the file.

The problem code starts here:

https://github.com/PowerShell/PowerShell/blob/38d582f038f31acfc1a748d60a5331eb82a3bd28/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/Common/InvokeRestMethodCommand.Common.cs#L387

if (ShouldWriteToPipeline)
{
   ...
}
else if (ShouldSaveToOutFile)
{
   ...
}

Notice that the logic outputs pipeline and skips the output to the file. Both ShouldWriteToPipeline and ShouldSaveToOutFile can be true so need to remove the else.

Steps to reproduce

Invoke-RestMethod https://taxonomyservice.azurefd.net/taxonomies/product-uri -PassThru -OutFile C:\temp\irm.json

Expected behavior

Output to console and to the file.

Actual behavior

Output to console only. The output file is not created.

Environment data

This affects all versions 5.1 and higher.

[iSazonov]

It doesn’t seem to make sense to write decoded object to pipeline and raw data to output file.

Then still the question is what kind of behavior do we want:

1. Write decoded object to pipeline and write decoded object to output file
2. Write decoded object to pipeline and write raw data to output file
3. Write raw data to pipeline and write raw data to output file
4. Write raw data to pipeline and write decoded object to output file

Since there is already buffered stream in one code path any scenario could be implemented.

[iSazonov]

When you write to the file, it writes the raw data stream.

Why would we need a raw data? I’d expect we write to file end objects converted to strings.