Powershell: new feature: wilcards everywere

[p0W3RH311]

process multiple property in same time simplified syntax

PS C:\> $a = @{
>>    test1 = 10
>>    test2 = 20
>>    test3 = 30
>>   test4 = 40
>> }

fo example for assign new value to properties types instead of

$a | % { 
   $_.test1 = 100
   $_.test2 = 100
   $_.test3 = 100
   $_.test3 = 100
 }

we use wildcard

for all properties

$a | % { 
   $_.test* = 100
 }

or for some property $_.test1 and $_.test2

$a | % { 
   $_.test*[12] = 100
 }

its powerful

[vexx32]

This would break parsing of the * operator which currently handles mathematical multiplication operations:

$a.test = 100
$a.test*= 100
$a.test # result: 10000

Equally, since * is a valid property and hashtable key name if enclosed in quotes, this would be a breaking change here also:

$a."test*" = 100
$a # will show the key "test*" with a value of 100

You can currently retrieve properties with a wildcard: [pscustomobject]$a | ForEach-Object -MemberName test* but I'm not sure there's a way to set them.

[mklement0]

Good points, @vexx32.

As for _setting_ wildcard-matched properties:

$o = [pscustomobject] @{ test1 = 10; test2 = 20; test3 = 30 ; test4 = 40 }
$o.psobject.Properties.Name -like 'test*' | % { $o.$_ = 100 }

[SeeminglyScience]

There's also some built in syntax for it (sorta) with the "magic" methods:

$o = [pscustomobject] @{ test1 = 10; test2 = 20; test3 = 30 ; test4 = 40 }
$o.psobject.Properties.Match('test*').ForEach('Value', 100)
$o
# test1 test2 test3 test4
# ----- ----- ----- -----
#   100   100   100   100

[mklement0]

That's handy, @SeeminglyScience.

I assume you're calling it "magic" because the actual collection type returned by .psobject.Properties doesn't have this method.

Out of curiosity: is there any way to systematically discover all this "magic" throughout PowerShell?
It would be great if the Get-Member enhancement discussed in #11798 would cover them all.

[vexx32]

@mklement0 the .PSObject.Properties member does have the .Match() method definition, it's defined by the ReadOnlyPSMemberInfoCollection type, which is one of the types that that particular collection inherits. (thanks @mklement0 for the correction; it is in fact PSMemberInfo<T> that implements this member.)

So that won't really be covered there, but you can discover it the same way you would other things of that nature:

$a = @{}

Get-Member -InputObject $a.PSObject.Properties

[mklement0]

Thanks, @vexx32 - I got myself confused too:

While ReadOnlyPSMemberInfoCollection`1 too has a Match method, it isn't the type providing the Match method on the type returned from .psobject.Properties (and psobject.Members) - instead, it is the type returned _from calling Match_ on the latter.

The type providing Match for .psobject.Properties is System.Management.Automation.PSMemberInfoCollection`1, which the internal System.Management.Automation.PSMemberInfoIntegratingCollection`1 type that .psobject.Properties returns an instance of inherits from.

That said, you're right in essence: Get-Member is sufficient to discover the method.

[SeeminglyScience]

PSMemberInfoCollection<> is the base type that defines Match. By magic I meant that the ForEach magic method can be used to set a value.

[mklement0]

Thanks for clarifying, @SeeminglyScience (the word Collection was missing from the type name in my previous comment (since corrected) - System.Management.Automation.PSMemberInfoCollection`1 is indeed what I meant).

As for the word "magic", to close the tangent: let me again suggest the terminology "automatic method", following the pattern of "automatic variable" - after all, it's not magic; it is built in, and therefore _automatically available_.

[SeeminglyScience]

If someone googles automatic method they're not gonna find anything. Get it official and documented and I'll switch 🙂

I'll save any naming critiques for where ever that issue is

[mklement0]

Yes, having _established, agreed-upon terminology_ is very important - not just for discoverability, but also for rasing awareness of the underlying _concepts_.

_Establishing_ terminology is hard, not least because not everyone is focused on the importance of doing so.

https://github.com/PowerShell/PowerShell/issues/11798#issuecomment-583426062 first proposed the term _automatic member_, and it seemed like an apt place to start the discussion, given the context of suggesting that such members for the first time be made _programmatically discoverable_.

But you're right: let us tackle this directly: please see https://github.com/MicrosoftDocs/PowerShell-Docs/issues/5627

[iRon7]

Related: Enhance hash table syntax #13817: 1..4 | New-Dictionary -KeyScriptBlock { "Test$_" } -ValueScriptBlock { 10 * $_ }