One of the things we chatted about was when I first saw PowerShell.I was in the back of a big hall in LA, attending PDC 2003, and watched Jim Truer and Jeffrey Snover give Monad, as it was then called, its initial airing. I got quite excited – and waved a US$20 bill in the air and proclaimed “I’ll buy it now”! Jeffrey wisely declined, but many years later (and a bit worse for wear), I finally presented the $20 to him at an event in Redmond. You can see the $20 here and here!
It was one of those events I’ll not forget – it began a passion that continues to this day. As I say on the interview, nothing that has happened since – the community, the wealth of cmdlets, etc – has been a surprise at all. About the only surprise is that it’s taken a bit longer than I’d have hoped.
I recall the moment of amusement when Jeffrey Snover revealed the #Requires PowerShell statement when the first release of PowerShell V2 occurred. It had been in PowerShell V1, but was a very tight secret. As it turns out, with V2’s beta, the #Requires statement had additional functionality, as I pointed out in a recent blog post. With the release of V2 coming sooner rather than later, the question is whether this statement is rich enough (and whether it can get improved in V2). But let me explain what I mean by that.
The concept that a script or even a function/cmdlet requires some set of pre-requisites is obvious. If, for example, I have a script that relies on the Quest AD cmdlets, then I’d like to impose a rule that says the script needs those cmdlets. There’s no point me running any script that requires something not present on my system. I belive I should not only be able to describe this requirement, and that autohelp should provide that information.
The #Requires statement come some way towards meeting this general requirement. But I think it needs more than that. For me, the question becomes: what does a script need to ‘require’ and more importantly, how does it signal that need? As I see it, that means two separate questions: what do you NEED, distinct from how to express that requirement.
The second question taken first – I am not sure that just using the '#Requires statement is enough. As I think about it the need should be expressed in Powershell autohelp. Autohelp is that set of instructions that you can put at the start of a function, module or script that can leter provide help for users of your code.
I realise that the intention of autohelp was to, oddly enough, help. It seems to me that this can also be used to express the need that chunk of functionality might have a module/script/function for some pre-req. So I think that the should be a .REQUIRES statment in auto help, for example:
<#
...
.Requires
VERSION 2
MODULE Quest-ADTools
DLL tfl.reallycoolDLL.dl
ELEVATION
ASSEMBLY globalknowledge.powershell.ocs2007r2
...
#>
You should not only document the requirements but demand them in this Autohelp block (ie the autohelp block is more than just documentation). This would be a very elegant solution.
But separate to HOW you express the pre-reqs, I think V2 needs to expand what #Requires provides. Specially, I’d like to see the #REQUIRES statement expanded to allow you to specify:
A specific module
Elevation (should it need to run elevated)
A specific named DLL
A specify Assembly (i.e. in the GAC)
etc
I’d like to see the advanced function’s autohelp block be really useful!
Another interesting PowerShell tidbit. Alexandair has documented a bit more information about the #Requires statement in PowerShell. As he described in PowerShellers: The "#requires" statement, the #Requires statement has been in PowerShell since Version 1 (but was undocumented and not communicated widely!).
What’s neat is what else #Requires can do. The #Requires statement can also mandate a particular shell ID (i.e. this script only runs under a particular shell id) or that a particular snap-in is loaded (e.g. the Quest Active Roles tools).
This is more goodness in terms of Enterprise-readyness. I’d like to see what else could be added to the #Requires statement. Any thoughts?
