Commands/PostProcessing/PostProcess-InitializeAutomaticVariable.ps.ps1
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PipeScript.PostProcess function InitializeAutomaticVariables { <# .SYNOPSIS Initializes any automatic variables .DESCRIPTION Initializes any automatic variables at the beginning of a script block. This enables Automatic?Variable* and Magic?Variable* commands to be populated and populated effeciently. For example: * If a function exists named Automatic.Variable.MyCallstack * AND $myCallStack is used within a ScriptBlock Then the body of Automatic.Variable.MyCallstack will be added to the top of the ScriptBlock. .EXAMPLE # Declare an automatic variable, MyCallStack Import-PipeScript { Automatic.Variable function MyCallstack { Get-PSCallstack } } # Now we can use $MyCallstack as-is. # It will be initialized at the beginning of the script { $MyCallstack } | Use-PipeScript #> param( [vfp(Mandatory,ParameterSetName='ScriptBlock')] [scriptblock] $ScriptBlock, [vfp(Mandatory,ParameterSetName='FunctionDefinition')] [Management.Automation.Language.FunctionDefinitionAst] $FunctionDefinitionAst ) begin { # First, let's find all commands that automatic or magic variables. # Let's find all possible commands by wildcards (Automatic?Variable* or Magic?Variable*) $allAutomaticVariableCommands = @(Get-PipeScript -PipeScriptType AutomaticVariable) # Then, let's create a lookup table by the name of the automatic variable $allAutomaticVariables = [Ordered]@{} foreach ($automaticVariableCommand in $allAutomaticVariableCommands) { if ($automaticVariableCommand.VariableName) { $allAutomaticVariables[$automaticVariableCommand.VariableName] = $automaticVariableCommand } } # Declare a quick filter to get the definition of the automatic variable filter GetAutomaticVariableDefinition { $automaticVariableCommand = $_ if (-not $automaticVariableCommand) { $automaticVariableCommand = $args } # Resolve any alias as far as we can while ($automaticVariableCommand -is [Management.Automation.AliasInfo]) { $automaticVariableCommand = $automaticVariableCommand.ResolvedCommand } # If we've resolved to a function if ($automaticVariableCommand -is [Management.Automation.FunctionInfo]) { # take a quick second to check that the function is "right" if (-not $automaticVariableCommand.ScriptBlock.Ast.Body.EndBlock) { Write-Error "$automaticVariableCommand does not have an end block" } elseif (-not $automaticVariableCommand.ScriptBlock.Ast.Body.EndBlock.Unnamed) { Write-Error "$automaticVariableCommand end block should not be named" } else { # if it is, inline it's scriptblock (trimmed of some whitespace). "$($automaticVariableCommand.ScriptBlock.Ast.Body.EndBlock.ToString())" -replace '^\s{0,}param\(\)' -replace '^\s{0,}' -replace '\s{0,}$' } } # If we've resolved to a cmdlet elseif ($automaticVariableCommand -is [Management.Automation.CmdletInfo]) { # call it directly "$($automaticVariableCommand)" } } } process { $inObj = $_ if ($psCmdlet.ParameterSetName -eq 'FunctionDefinition') { $ScriptBlock = [scriptblock]::Create($FunctionDefinitionAst.Body -replace '^\{' -replace '\}$') } # Find all Variables $knownFunctionExtent = $null $allVariables = @($ScriptBlock | Search-PipeScript -AstCondition { param($ast) if ($ast -is [Management.Automation.Language.FunctionDefinitionAst]) { $knownFunctionExtent = $ast.Extent } if ($ast -isnot [Management.Automation.Language.VariableExpressionAST]) { return $false } if ($ast.Splatted) { return $false} if ($knownFunctionExtent -and $ast.Extent.StartOffset -ge $knownFunctionExtent.StartOffset -and $ast.Extent.EndOffset -lt $knownFunctionExtent.EndOffset) { return $false } if ($ast.Parent -is [Management.Automation.Language.AssignmentStatementAst] -and $ast.Parent.Left -eq $ast) { return $false } return $true } -Recurse | Select-Object -ExpandProperty Result) # If there were no variables in this script block, return. return if -not $allVariables # Let's collect all of the variables we need to define $prependDefinitions = [Ordered]@{} foreach ($var in $allVariables) { $variableName = "$($var.VariablePath)" # If we have an automatic variable by that variable name if ($allAutomaticVariables[$variableName]) { # see if it's assigned anywhere before here $assigned = @($var.GetAssignments()) # see if it's assigned anywhere before here continue if $assigned -and $assigned.Extent.StartOffset -le $var.Extent.StartOffset # stringify it's script block and add it to our dictionary of prepends $prependDefinitions[$variableName] = $allAutomaticVariables[$variableName] | GetAutomaticVariableDefinition } } # If we don't need to prepend anything, return return if -not $prependDefinitions.Count $AlreadyPrepended = @() # Otherwise, make it all one big string. $toPrepend = @(foreach ($toPrepend in $prependDefinitions.GetEnumerator()) { $variableName = $toPrepend.Key if ($AlreadyPrepended -contains $variableName) { continue } $variableValue = $toPrepend.Value if ($variableValue -notmatch '^\@[\(\{\[]' -or $variableValue -match '[\r\n]') { $variableValue = "`$($variableValue)" } # Define the automatic variable by name $(if ($variableName -match '\p{P}') { # (if it had punctuation) "`${$($variableName)}" # enclose in brackets } else { # otherwise "`$$($variableName)" # just use $VariableName }) + '=' + "$variableValue" # prepend the definition of the function. # Why? Because this way, the automatic variable is declared at the same scope as the ScriptBlock. # (By the way, this means you cannot have _any_ parameters on an automatic variable) $AlreadyPrepended += $variableName }) -join [Environment]::newLine # Turn our big string into a script block $toPrepend = [ScriptBlock]::create($toPrepend) # and prepend it to this script block. $updatedScriptBlock = Update-ScriptBlock -ScriptBlock $scriptBlock -Prepend $toPrepend switch ($psCmdlet.ParameterSetName) { ScriptBlock { $updatedScriptBlock } FunctionDefinition { [scriptblock]::Create( @( "$(if ($FunctionDefinitionAst.IsFilter) { "filter"} else { "function"}) $($FunctionDefinitionAst.Name) {" $UpdatedScriptBlock "}" ) -join [Environment]::NewLine ).Ast.EndBlock.Statements[0] } } } } |