For better DSL

this code work

function a 
{
   b {
        write-host 'hello'
   }
}

function b 
{
   param([scriptblock]$sb)
   &$sb
}

but this don't work because the character {

function a 
{
   b 
  {
        write-host 'hello'
   }
}

function b 
{
   param([scriptblock]$sb)
   &$sb
}

PS C:\> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      6.0.0-rc.2
PSEdition                      Core
GitCommitId                    v6.0.0-rc.2
OS                             Microsoft Windows 6.3.9600
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

I can't see how this could ever be added.

b
{
    write-host 'hello'
}

Would currently returns the result of b and scriptblock. That may be desirable and changing the behavior would break the old behavior. This will probably not be doable with functions, but perhaps a new language keyword to distinguish DSL elements.

something like

function a 
{
   b 
  {
        write-host 'hello'
   }
}

DSLfunction b 
{
   param([scriptblock]$sb)
   &$sb
}

This is the reason I highly recommend OTBS or Stroustrup indentation in PowerShell. There are far fewer places you can use Allman and friends.

Dynamic keywords enable this scenario (first introduced with DSC).

This #3169 was an attempt at properly supporting DSLs in PowerShell.

Jason Shirk (@lzybkr)

Jason Shirk (@lzybkr) awesome!
p0W3RH311

here is how you could make that work now:

$keyword = [System.Management.Automation.Language.DynamicKeyword]@{
    Keyword ="b"
    BodyMode = [Management.Automation.Language.DynamicKeywordBodyMode]::ScriptBlock
    NameMode = [Management.Automation.Language.DynamicKeywordNameMode]::NoName
}
[System.Management.Automation.Language.DynamicKeyword]::AddKeyword($keyword)

function a 
{
   b 
  {
        write-host 'hello'
   }
}

function b 
{
    param (
        [Management.Automation.Language.DynamicKeyword] $KeywordData,
        $Name,
        [ScriptBlock] $Value,
        $SourceMetaData,
        $InstanceName
    )
   & $Value
}

a

Mark Kraus (@markekraus)

Mark Kraus (@markekraus)

PowerShell v6.0.0-rc.2
Copyright (c) Microsoft Corporation. All rights reserved.

https://aka.ms/pscore6-docs
Type 'help' to get help.


PS C:\Users\My\Desktop> & 'C:\Users\My\Desktop\TEST.PS1'
The expression after '&' in a pipeline element produced an object that was not valid. It must result in a command n
ame, a script block, or a CommandInfo object.
At C:\Users\My\Desktop\TEST.PS1:25 char:6
+    & $Value
+      ~~~~~~
+ CategoryInfo          : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : BadExpression


        write-host 'hello'

Jason Shirk (@lzybkr)

Heh.. that's weird. works if I do this:

Test.ps1:

$keyword = [System.Management.Automation.Language.DynamicKeyword]@{
    Keyword ="b"
    BodyMode = [Management.Automation.Language.DynamicKeywordBodyMode]::ScriptBlock
    NameMode = [Management.Automation.Language.DynamicKeywordNameMode]::NoName
}
[System.Management.Automation.Language.DynamicKeyword]::AddKeyword($keyword)

. .\Test2.ps1

Test2.ps1:

function b 
{
    param (
        [Management.Automation.Language.DynamicKeyword] $KeywordData,
        $Name,
        [ScriptBlock] $Value,
        $SourceMetaData,
        $InstanceName
    )
   & $Value
}

function a 
{
   b 
  {
        write-host 'hello'
   }
}

a

then run & .\Test.ps1

When I was tasting this out I was doing it with the interactive console on VS Code and executing a block at a time. It appears to not work when used in the same execution block, but if you can separate it out it works. i dunno. I didn't even know this existed until Jason Shirk (@lzybkr)'s comment in this issue.

There's a reason it's not formally supported yet.

Yes, the parser has rules in it for DynamicKeywords that let you do things like hang the braces, and #3169 extends that so you can nest keyword contexts, but there are still issues with making the keyword functionality robust and predictable enough and they require some work to solve.

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

This issue has been marked as "No Activity" as there has been no activity for 6 months. It has been closed for housekeeping purposes.

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For better DSL #6194

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markekraus commented on Feb 20, 2018

lzybkr commented on Feb 20, 2018

markekraus commented on Feb 20, 2018

p0W3RH311 commented on Feb 22, 2018

markekraus commented on Feb 22, 2018

lzybkr commented on Feb 22, 2018

rjmholt commented on Feb 23, 2018

microsoft-github-policy-service commented on Nov 16, 2023

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microsoft-github-policy-service commented on Nov 16, 2023

microsoft-github-policy-service commented on Nov 23, 2023

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