Adding 'new' keyword (#128)

Author: James Brundage

Transpilers/Keywords/New.psx.ps1

@@ -0,0 +1,133 @@
+<#
+.SYNOPSIS
+    'new' keyword
+.DESCRIPTION
+    This transpiler enables the use of the keyword 'new'.
+
+    new acts as it does in many other languages.  
+    
+    It creates an instance of an object.
+
+    'new' can be followed by a typename and any number of arguments or hashtables.
+
+    If 'new' is followed by a single string, and the type has a ::Parse method, new will parse the value.
+
+    If 'new' 
+.EXAMPLE
+    .> { new DateTime }
+.EXAMPLE
+    .> { new byte 1 }
+.EXAMPLE
+    .> { new int[] 5 }
+.EXAMPLE
+    .> { new datetime 12/31/1999 }
+.EXAMPLE
+    .> { new @{RandomNumber = Get-Random; A ='b'}}
+.EXAMPLE
+    .> { new Diagnostics.ProcessStartInfo @{FileName='f'} }
+#>
+[ValidateScript({
+    $CommandAst = $_
+    return ($commandAst -and $CommandAst.CommandElements[0].Value -eq 'new')
+})]
+param(
+[Parameter(Mandatory,ValueFromPipeline)]
+[Management.Automation.Language.CommandAst]
+$CommandAst
+)
+
+process {
+    $null, $newTypeName, $newArgs = $CommandAst.CommandElements
+    $maybeGeneric = $false
+    $propertiesToCreate   = @()
+
+    $newTypeName = 
+        # Non-generic types will be a bareword constant        
+        if ($newTypeName.Value) {
+            $newTypeName.Value
+        } 
+        elseif ($newTypeName -is [Management.Automation.Language.HashtableAst]) {
+            $propertiesToCreate += $newTypeName
+        }
+        else {
+            # generic types will be an ArrayLiteralAst
+            $maybeGeneric = $true
+            $newTypeName.Extent.ToString()
+        }
+    if ($newTypeName -match '^\[' -and $newTypeName -match '\]$' ) {
+        $newTypeName = $newTypeName -replace '^\[' -replace '\]$'
+    }
+    
+
+    
+    $constructorArguments = @(
+        foreach ($newArg in $newArgs) {
+            # If the argument is a hashtable, treat it as properties to set after creation.
+            if ($newArg -is [Management.Automation.Language.HashtableAst]) {
+                $propertiesToCreate += $newArg
+            } else {
+            # Otherwise, treat it as arguments.
+                $newArg
+            }
+        }
+    )
+
+    $constructorArguments = @(
+        foreach ($constructorArg in $constructorArguments) {
+            if ($constructorArg.StringConstantType -eq 'BareWord') {
+                "'" + $constructorArg.Value.Replace("'","''") + "'"
+            } else {
+                $constructorArg
+            }
+        }
+    )
+
+    $realNewType = $newTypeName -as [type]
+    if (-not $realNewType -and $maybeGeneric) {
+        $realNewType = "Collections.Generic.$newTypeName" -as [type]
+        if ($realNewType) {
+            $newTypeName = "Collections.Generic.$newTypeName"
+        }
+    }
+
+    $newNew = 
+        if ($realNewType) {
+            if ($realNewType::parse -and 
+                $constructorArguments.Length -eq 1 -and 
+                $constructorArguments[0] -is [string]) {
+                "[$newTypeName]::parse(" + ($constructorArguments -join ',') + ")"
+            } elseif ($realNewType::new) {
+                "[$newTypeName]::new(" + ($constructorArguments -join ',') + ")"
+            } elseif ($realNewType.IsPrimitive) {
+                if ($constructorArguments) {
+                    if ($constructorArguments.Length -eq 1) {
+                        "[$newTypeName]$constructorArguments"    
+                    } else {
+                        "[$newTypeName]($($constructorArguments -join ','))"
+                    }                    
+                } else {
+                    "[$newTypeName]::new()"
+                }
+            }
+        } elseif ($propertiesToCreate.Count -eq 1 -and -not $newTypeName) {
+            "[PSCustomObject][Ordered]$propertiesToCreate"
+        } else {
+            Write-Error "Unknown type '$newTypeName'"                        
+            return
+        }
+
+    if ($propertiesToCreate -and $newTypeName) {
+        $newNew = '$newObject = ' + $newNew + [Environment]::NewLine
+        $newNew += (@(foreach ($propSet in $propertiesToCreate) {
+            'foreach ($kvp in ' + "([Ordered]" + $propSet + ').GetEnumerator()) {
+    $newObject.$($kvp.Key) = $kvp.Value
+}'
+        }) -join [Environment]::NewLine)
+        $newNew += [Environment]::NewLine + '$newObject'
+        $newNew = "`$($newNew)"
+    }
+
+    if ($newNew) {
+        [scriptblock]::Create($newNew)
+    }
+}

Transpilers/Keywords/README.ps1.md

@@ -0,0 +1,29 @@
+This directory and it's subdirectories contain additional language keywords within PipeScript.
+
+Most keywords will be implemented as a Transpiler that tranforms a CommandAST.
+
+~~~PipeScript{
+    [PSCustomObject]@{
+        Table = Get-Transpiler -TranspilerPath $pwd |
+            Select-Object DisplayName, Synopsis, @{
+                Name='Link'
+                Expression = { $_.Name }
+            }
+    }}
+~~~
+
+
+~~~PipeScript{
+    @(foreach ($transpiler in Get-Transpiler -TranspilerPath $pwd) {
+        $examples = @($transpiler.Examples)
+        if (-not $examples) { continue }
+        for ($exampleNumber = 1; $exampleNumber -le $examples.Length; $exampleNumber++) {
+            @("## $($transpiler.DisplayName) Example $($exampleNumber)", 
+                [Environment]::Newline,
+                "~~~PowerShell",                
+                $examples[$exampleNumber - 1],                
+                "~~~") -join [Environment]::Newline
+        }        
+    }) -join ([Environment]::Newline * 2)
+}
+~~~