Transpilers/Syntax/ConditionalKeyword.psx.ps1
|
<# .SYNOPSIS Conditional Keyword Expansion .DESCRIPTION Allows for conditional Keywords. A coniditional keyword is a continue or break statement, followed by a partial if clause. The following keywords can be used conditionally: |Keyword |Example | |---------|----------------- | |break |`break if $true` | |continue |`continue if $true`| |return |`return if $true` | |throw |`throw if $true` | .EXAMPLE Invoke-PipeScript { $n = 1 do { $n = $n * 2 $n break if (-not ($n % 16)) } while ($true) } .EXAMPLE Import-PipeScript { function Get-Primes([ValidateRange(2,64kb)][int]$UpTo) { $KnownPrimes = new Collections.ArrayList @(2) $SieveOfEratosthenes = new Collections.Generic.Dictionary[uint32,bool] $n = 2 :nextNumber for (; $n++;) { # Break if past our point of interest break if ($n -ge $upTo) # Skip if an even number continue if (-not ($n -band 1)) # Check our sieve continue if $SieveOfEratosthenes.ContainsKey($n) # Determine half of the number $halfN = $n /2 # If this is divisible by the known primes foreach ($k in $knownPrimes) { continue nextNumber if (($n % $k) -eq 0) {} break if ($k -ge $halfN) } foreach ($k in $knownPrimes) { $SieveOfEratosthenes[$n * $k] = $true } $null = $knownPrimes.Add($n) } $knownPrimes -le $UpTo } } #> [ValidateScript({ $ast = $_ # If the AST is not a break, continue, return, or throw statement if ($ast -isnot [Management.Automation.Language.ContinueStatementAst] -and $ast -isnot [Management.Automation.Language.BreakStatementAst] -and $ast -isnot [Management.Automation.Language.ReturnStatementAst] -and $ast -isnot [Management.Automation.Language.ThrowStatementAst] ) { return $false # it is not valid for this transpiler. } # If there is no pipeline if (-not $ast.Pipeline) { # find the next statement $nextStatement = $ast.Parent.Statements[$ast.Parent.Statements.IndexOf($ast) + 1] # (If there isn't one, it's invalid) if (-not $nextStatement) { return $false } # If the label was 'if', it's valid. if ('if' -eq $ast.Label) { return $true } # If the label is not if, it could be an actual label # If the next statement is an if Statement, we're good if ($nextStatement -is [Management.Automation.Language.IfStatementAst]) { return $true } # If it wasn't, it's valid return $false } else { # If there is a pipeline, it must start with 'if' return $ast.Pipeline -match '^if' } })] param( # A Continue Statement. [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='ContinueStatement')] [Management.Automation.Language.ContinueStatementAst] $ContinueStatement, # A Break Statement. [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='BreakStatement')] [Management.Automation.Language.BreakStatementAst] $BreakStatement, # A Return Statement. [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='ReturnStatement')] [Management.Automation.Language.ReturnStatementAst] $ReturnStatement, # A Throw Statement. [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='ThrowStatement')] [Management.Automation.Language.ThrowStatementAst] $ThrowStatement ) process { # Get the statement that will be transformed $statement = $($PSBoundParameters[$PSBoundParameters.Keys -like '*Statement']) # (and return if we do not find one) if (-not $statement) { return } # Force the statement to be lowercase $statementType = ($statement.GetType().Name -replace 'StatementAst').ToLower() # There are two types of conditional keywords: # Labeled statements (continue/break) # Pipelined statements (return/throw) # For labeled statements, we will need to skip until a point $skipUntil = $null # For pipelined statements, we need to collect and script expression clauses $PipelineClauses = @() $nextStatement = # If we are dealing with a labeled statement if (-not $statement.Pipeline) { # we will always skip the next statement $skipUntil = $statement.Parent.Statements[$statement.Parent.Statements.IndexOf($statement) + 1] $skipUntil } else { # Otherwise, go thru all command elements in the pipeline $firstElement = $statement.Pipeline.PipelineElements[0] # (skipping the first) $commandElements = $firstElement.CommandElements[1..($firstElement.CommandElements.Count)] foreach ($CommandElement in $commandElements) { # any script block expression makes up the closing clause if ($commandElement -is [Management.Automation.Language.ScriptBlockExpressionAst]) { $PipelineClauses += $CommandElement.ScriptBlock.AsScriptBlock() } else { # and all other command elements make up the condition. $CommandElement } } } $(if ($nextStatement -is [Management.Automation.Language.IfStatementAst]) { # If the next statement was an if, recreate it's first clause [ScriptBlock]::Create("if ($($nextStatement.Clauses[0].Item1)) { $( $ReplacedClause = $nextStatement.Clauses[0].Item2 -replace '^\s{0,}\{\s{0,}' -replace '\s{0,}\}\s{0,}$' # If the clause was not empty, if ($ReplacedClause) { # add continue or break to the label. $ReplacedClause + ';' + "$statementType $($statement.Label)" } else { # otherwise, continue or break to the label. "$statementType $($statement.Label)" } ) }") } elseif ($PipelineClauses) { # If we had pipeline clauses, include them as is. [ScriptBlock]::Create("if ($nextStatement) { $statementType $pipelineClauses}") } else { # Otherwise, make a simple if statement. [ScriptBlock]::Create("if ($nextStatement) { $statementType }") }) | Add-Member NoteProperty SkipUntil $skipUntil -PassThru } |