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James Brundage
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Adding support for Dotting (#107)
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‎Transpilers/Syntax/Dot.psx.ps1

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<#
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.SYNOPSIS
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Dot Notation
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.DESCRIPTION
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Dot Notation simplifies multiple operations on one or more objects.
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Any command named . (followed by a letter) will be treated as the name of a method or property.
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.Name will be considered the name of a property or method
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If it is followed by parenthesis, these will be treated as method arguments.
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If it is followed by a ScriptBlock, a dynamic property will be created that will return the result of that script block.
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If any other arguments are found before the next .Name, they will be considered arguments to a method.
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.EXAMPLE
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.> {
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[DateTime]::now | .Month .Day .Year
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}
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.EXAMPLE
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.> {
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"abc", "123", "abc123" | .Length
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}
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.EXAMPLE
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.> { 1.99 | .ToString 'C' [CultureInfo]'gb-gb' }
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.EXAMPLE
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.> { 1.99 | .ToString('C') }
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.EXAMPLE
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1..5 | .Number { $_ } .Even { -not ($_ % 2) } .Odd { ($_ % 2) -as [bool]}
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#>
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[ValidateScript({
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$commandAst = $_
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$DotChainPattern = '^\.\p{L}'
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if ($commandAst.CommandElements[0].Value -match '^\.\p{L}') {
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return $true
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}
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return $false
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})]
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param(
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[Parameter(Mandatory,ParameterSetName='Command',ValueFromPipeline)]
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[Management.Automation.Language.CommandAst]
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$CommandAst
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)
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begin {
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$DotProperty = {
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if ($in.PSObject.Methods[$PropertyName].OverloadDefinitions -match '\(\)$') {
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$in.$PropertyName.Invoke()
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} elseif ($in.PSObject.Properties[$PropertyName]) {
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$in.$PropertyName
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}
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}
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$DotMethod = { $in.$MethodName($MethodArguments) }
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}
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process {
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# Create a collection for the entire chain of operations and their arguments.
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$DotChain = @()
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$DotArgsAst = @()
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$DotChainPart = ''
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$DotChainPattern = '^\.\p{L}'
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# Then, walk over each element of the commands
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$CommandElements = $CommandAst.CommandElements
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for ( $elementIndex =0 ; $elementIndex -lt $CommandElements.Count; $elementIndex++) {
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# If we are on the first element, or the command element starts with the DotChainPattern
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if ($elementIndex -eq 0 -or $CommandElements[$elementIndex].Value -match $DotChainPattern) {
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if ($DotChainPart) {
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$DotChain += [PSCustomObject]@{
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PSTypeName = 'PipeScript.Dot.Chain'
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Name = $DotChainPart
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Arguments = $DotArgsAst
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}
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}
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$DotArgsAst = @()
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# A given step started with dots can have more than one step in the chain specified.
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$elementDotChain = $CommandElements[$elementIndex].Value.Split('.')
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[Array]::Reverse($elementDotChain)
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$LastElement, $otherElements = $elementDotChain
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if ($otherElements) {
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foreach ($element in $otherElements) {
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$DotChain += [PSCustomObject]@{
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PSTypeName = 'PipeScript.Dot.Chain'
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Name = $element
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Arguments = @()
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}
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}
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}
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$DotChainPart = $LastElement
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}
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# If we are not on the first index or the element does not start with a dot, it is an argument.
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else {
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$DotArgsAst += $CommandElements[$elementIndex]
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}
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}
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if ($DotChainPart) {
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$DotChain += [PSCustomObject]@{
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PSTypeName = 'PipeScript.Dot.Chain'
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Name = $DotChainPart
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Arguments = $DotArgsAst
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}
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}
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$NewScript = @()
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$indent = 0
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$WasPipedTo =
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$CommandAst.Parent -and
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$CommandAst.Parent.PipelineElements -and
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$CommandAst.Parent.PipelineElements.IndexOf($CommandAst) -gt 0
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# By default, we are not creating a property bag.
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# This default will change if:
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# * More than one property is defined
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# * A property is explicitly assigned
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$isPropertyBag = $false
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# If we were piped to, adjust indent (for now)
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if ($WasPipedTo ) {
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$indent += 4
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}
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# Declare the start of the chain (even if we don't use it)
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$propertyBagStart = (' ' * $indent) + '[PSCustomObject][Ordered]@{'
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# and keep track of all items we must post process.
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$PostProcess = @()
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# If more than one item was in the chain
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if ($DotChain.Length -ge 0) {
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$indent += 4 # adjust indentation
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}
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# Walk thru all items in the chain of properties.
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foreach ($Dot in $DotChain) {
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$firstDotArg, $secondDotArg, $restDotArgs = $dot.Arguments
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# Determine what will be the segment of the dot chain.
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$thisSegement =
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# If the dot chain has no arguments, treat it as a property
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if (-not $dot.Arguments) {
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$DotProperty -replace '\$PropertyName', "'$($dot.Name)'"
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}
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# If the dot chain's first argument is an assignment
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elseif ($firstDotArg -is [Management.Automation.Language.StringConstantExpressionAst] -and
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$firstDotArg.Value -eq '=') {
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$isPropertyBag = $true
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# and the second is a script block
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if ($secondDotArg -is [Management.Automation.Language.ScriptBlockExpressionAst]) {
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# it will become either a [ScriptMethod] or [ScriptProperty]
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$secondScriptBlock = [ScriptBlock]::Create(
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$secondDotArg.Extent.ToString() -replace '^\{' -replace '\}$'
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)
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# If the script block had parameters (even if they were empty parameters)
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# It should become a ScriptMethod
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if ($secondScriptBlock.Ast.ParamBlock) {
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"[PSScriptMethod]::New('$($dot.Name)', $secondDotArg)"
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} else {
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# Otherwise, it will become a ScriptProperty
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"[PSScriptProperty]::New('$($dot.Name)', $secondDotArg)"
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}
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$PostProcess += $dot.Name
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}
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# If we had an array of arguments, and both elements were ScriptBlocks
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elseif ($secondDotArg -is [Management.Automation.Language.ArrayLiteralAst] -and
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$secondDotArg.Elements.Count -eq 2 -and
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$secondDotArg.Elements[0] -is [Management.Automation.Language.ScriptBlockExpressionAst] -and
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$secondDotArg.Elements[1] -is [Management.Automation.Language.ScriptBlockExpressionAst]
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) {
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# Then we will treat this as a settable script block
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$PostProcess += $dot.Name
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"[PSScriptProperty]::New('$($dot.Name)', $($secondDotArg.Elements[0]), $($secondDotArg.Elements[1]))"
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}
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elseif (-not $restDotArgs) {
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# Otherwise, if we only have one argument, use the expression directly
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$secondDotArg.Extent.ToString()
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} elseif ($restDotArgs) {
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# Otherwise, if we had multiple values, create a list.
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@(
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$secondDotArg.Extent.ToString()
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foreach ($otherDotArg in $restDotArgs) {
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$otherDotArg.Extent.Tostring()
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}
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) -join ','
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}
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}
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# If the dot chain's first argument is a ScriptBlock
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elseif ($firstDotArg -is [Management.Automation.Language.ScriptBlockExpressionAst])
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{
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# Run that script block
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"& $($firstDotArg.Extent.ToString())"
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}
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elseif ($firstDotArg -is [Management.Automation.Language.ParenExpressionAst]) {
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# If the first argument is a parenthesis, assume the contents to be method arguments
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$DotMethod -replace '\$MethodName', $dot.Name -replace '\(\$MethodArguments\)',$firstDotArg.ToString()
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}
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else {
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# If the first argument is anything else, assume all remaining arguments to be method parameters.
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$DotMethod -replace '\$MethodName', $dot.Name -replace '\(\$MethodArguments\)',(
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'(' + ($dot.Arguments -join ',') + ')'
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)
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}
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# Now we add the segment to the total script
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$NewScript +=
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if (-not $isPropertyBag -and $DotChain.Length -eq 1 -and $thisSegement -notmatch '^\[PS') {
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# If the dot chain is a single item, and not part of a property bag, include it directly
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"$(' ' * ($indent - 4))$thisSegement"
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} else {
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$isPropertyBag = $true
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# Otherwise include this segment as a hashtable assignment with the correct indentation.
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$thisSegement = @($thisSegement -split '[\r\n]+' -ne '' -replace '$', (' ' * 8)) -join [Environment]::NewLine
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@"
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$(' ' * $indent)'$($dot.Name.Replace("'","''"))' =
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$(' ' * ($indent + 4))$thisSegement
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"@
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}
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}
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# If we were generating a property bag
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if ($isPropertyBag) {
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if ($WasPipedTo) { # and it was piped to
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# Add the start of the pipeline and the property bag start to the top of the script.
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$NewScript = @('& { process {') + ((' ' * $indent) + '$in = $this = $_') + $propertyBagStart + $NewScript
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} else {
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# If it was not piped to, just add the start of the property bag
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$newScript = @($propertyBagStart) + $NewScript
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}
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} elseif ($WasPipedTo) {
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# If we were piped to (but were not a property bag)
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$indent -= 4
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# add the start of the pipeline to the top of the script.
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$newScript = @('& { process {') + ((' ' * $indent) + '$in = $this = $_') + $NewScript
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}
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# If we were a property bag
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if ($isPropertyBag) {
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# close out the script
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$NewScript += ($(' ' * $indent) + '}')
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$indent -= 4
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}
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# If there was post processing
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if ($PostProcess) {
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# Change the property bag start to assign it to a variable
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$NewScript = $newScript -replace ($propertyBagStart -replace '\W', '\$0'), "`$Out = $propertyBagStart"
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foreach ($post in $PostProcess) {
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# and change any [PSScriptProperty] or [PSScriptMethod] into a method on that object.
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$newScript += "`$Out.PSObject.Members.Add(`$out.$Post)"
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}
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# Then output.
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$NewScript += '$Out'
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}
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# If we were piped to
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if ($WasPipedTo) {
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# close off the script.
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$NewScript += '} }'
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} else {
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# otherwise, make it a subexpression
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$NewScript = '$(' + ($NewScript -join [Environment]::NewLine) + ')'
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}
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$NewScript = $NewScript -join [Environment]::Newline
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# Return the created script.
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[scriptblock]::Create($NewScript)
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}

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