Pictured: The new -ResponseHeadersVariable parameter in action
I wanted to share with you another new feature added to the PowerShell Core Invoke-RestMethod Cmdlet: The -ResponseHeadersVariable parameter.
This feature will be available starting with PowerShell Core v6.0.0-beta.8 and is available now in the nightly builds or if you build it yourself from master.
Pictured: A packet capture of a current build of PowerShell Core submitting a multipart/form-data POST request from Invoke-WebRequest.
Over the past few months I have been donating a generous portion of my spare time to help improve the Web Cmdlets (Invoke-WebRequest and Invoke-RestMethod) in PowerShell Core. This is partly because I want and need certain functionality for both personal and work related projects. It is also because I have had some minor gripes about these Cmdlets for some time.
One common ask I have seen repeated in just about every PowerShell forum is multipart/form-data support. It seems like a reasonable thing to ask when there are many endpoints that will only work with a multipart/form-data submission. There is an open issue (#2112) on the PowerShell GitHub echoing the same request. It was brought to my attention and I decided to give it a serious look.
The result is that PowerShell Core now has partial multipart/form-data support in both Web Cmdlets. This change didn't make the cut for 6.0.0-beta.7 but it will be available starting in 6.0.0-beta.8 and is available now if you build it manually or grab the latest nightly build.
This blog will cover some of the challenges involved in supporting multipart/form-data, how to make use of this new feature, and about future plans for additional support.
Because typing multipart/form-data is annoying, I will be shortening it to just multipart. Please don't let this be mistaken for other multipart submission methods.
Also, I will be referring collectively to Invoke-WebRequest and Invoke-RestMethod as Web Cmdlets. In this case, there is no need to call out each command as they offer the same base functionality for multipart support.
