ScriptCop

1.5.2.0

Rules/Test-ForUnusedVariable.ps1

function Test-ForUnusedVariable
{
    #region ScriptTokenValidation Parameter Statement
    param(
    <#
    This parameter will contain the tokens in the script, and will be automatically
    provided when this command is run within ScriptCop.
     
    This parameter should not be used directly, except for testing purposes.
    #>
    [Parameter(ParameterSetName='TestScriptToken',
        Mandatory=$true,
        ValueFromPipelineByPropertyName=$true)]
    [Management.Automation.PSToken[]]
    $ScriptToken,
    
    <#
    This parameter will contain the command that was tokenized, and will be automatically
    provided when this command is run within ScriptCop.
     
    This parameter should not be used directly, except for testing purposes.
    #>
    [Parameter(ParameterSetName='TestScriptToken',Mandatory=$true,ValueFromPipelineByPropertyName=$true)]
    [Management.Automation.CommandInfo]
    $ScriptTokenCommand,
    
    <#
    This parameter contains the raw text of the script, and will be automatically
    provided when this command is run within ScriptCop
     
    This parameter should not be used directly, except for testing purposes.
    #>
    [Parameter(ParameterSetName='TestScriptToken',Mandatory=$true,ValueFromPipelineByPropertyName=$true)]
    [string]
    $ScriptText
    )
    #endregion ScriptTokenValidation Parameter Statement
    
    process {           
        $variablesAssignedAt = @{}
        $variablesReferencedAt = @{}
        $parametersAssignedAt = @{}
        $inParamBlock = $false
        $parenCount = 0
        $lastTokenWasVariable = $false 
        foreach ($token in $scriptToken) {
            if ($token.Type -eq 'Keyword' -and $token.Content -eq 'param') {
                if (-not ($foreach.MoveNext())) { break }                 
                $parenCount = 1 
                $inParamBlock = $true               
                continue
            }
            if ($inParamBlock -and $token.Type -like 'Group*') {
                if ($token.Content -eq ')') { $parenCount-- }
                if ($token.Content -eq '(') { $parenCount++ }
                if ($parenCount -eq 0) { $inParamBlock = $false } 
            }
            if ($lastTokenWasVariable -and -not $inParamBlock) {
                $variableName = $lasttoken.Content
                if ($token.Content -eq '=') {
                    if (-not ($variablesAssignedAt[$variableName])) {
                        $variablesAssignedAt[$variableName] = @()
                    }
                    $variablesAssignedAt[$variableName] += $lastToken
                } else {
                    if (-not ($variablesReferencedAt[$variableName])) {
                        $variablesReferencedAt[$variableName] = @()
                    }
                    $variablesReferencedAt[$variableName] += $lastToken
                }
                $lastTokenWasVariable = $false 

            }
            
            if ($token.Type -eq 'Variable') {
                $variableName = $token.Content
                $lastToken = $token
                $lastTokenWasVariable = $true                                 
            } elseif ($token.Type -eq 'string') {
                $variableRefType = '\$[{]*(?<variable>\w{1,})[}]*', '\@[{]*(?<variable>\w{1,})[}]*'
                foreach ($vrt in $variableRefType) {
                    $regex = New-Object Regex $vrt, 'Multiline, IgnoreCase'
                    foreach ($match in $regex.Matches($token.Content)) {
                        if (-not $match) { continue } 
                        $variableName = $match.Value.Replace('$', '').Replace('@', '').Replace('{','').Replace('}','')
                        if (-not ($variablesReferencedAt[$variableName])) {
                            $variablesReferencedAt[$variableName] = @()
                        }
                        $variablesReferencedAt[$variableName] += $token
                    }
                }
            }
        }

        foreach ($variableName in $variablesAssignedAt.Keys) {
            # built in variables that are often set to do other things get a pass
            if ('null', 'ofs' -contains $variableName) { continue } 
            # So do preference variables
            if ($variableName -like "*Preference") { continue } 

            # Script: assignments do as well, since they could be caching
            if ($variablename -like "script:*") {continue }
            if (-not $variablesReferencedAt[$variableName]) {
                $assignedAt = $variablesAssignedAt[$variableName]
                $assignedAtString = ($assignedAt | Select-Object @{
                    Name = 'Line'
                    Expression = { $_.StartLine}
                }, @{
                    Name = 'Column'
                    Expression = { $_.StartColumn}
                }) -join 
                    " and " -ireplace 
                    ';', '' -ireplace 
                    '@{', '' -ireplace
                    '}', ''
                Write-Error "`$$variableName is assigned to but never used. It is assigned at $assignedAtString"
            }
        }                        
   }
   
}