functions/Get-ExtensionAvailableTasks.ps1
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# <copyright file="Get-ExtensionAvailableTasks.ps1" company="Endjin Limited"> # Copyright (c) Endjin Limited. All rights reserved. # </copyright> function Get-ExtensionAvailableTasks { <# .SYNOPSIS Returns a list of all the task names defined within an extension. .DESCRIPTION This function is used to discover all of the tasks defined by an extension. It does this by creating a private implementation of the InvokeBuild 'task' DSL keyword that simply returns the task name as a string. This allows us to enumerate all of the tasks defined in the extension's tasks files, without knowing how many tasks are defined in any given file. .PARAMETER ExtensionPath The path to the root of the extension being searched. .EXAMPLE PS:> $taskNames = Get-ExtensionAvailableTasks -ExtensionPath c:\myExtension #> [CmdletBinding()] [OutputType([string])] param ( [Parameter(Mandatory=$true)] [string] $ExtensionPath ) # Special handling for when this function is called from within an InvokeBuild process (e.g. when this # function's Pester tests are run as part of the build process), whereby the 'task' keyword is already # defined as an Alias to 'Invoke-BuildTask' and will take precedence over our function override below. $aliasBackup = Get-Alias task -ErrorAction Ignore if ($aliasBackup) { Remove-Alias -Name task } $availableTasks = @() try { # Define a private override implementation for the 'task' keyword used in '*.tasks.ps1' files that # simply returns the task name as a string. We will use this as a simple mechanism to discover # all of the tasks defined in a given code file. function task { [CmdletBinding()] param ( [Parameter(Mandatory, Position = 0)] [string] $TaskName, [Parameter(ValueFromRemainingArguments)] $Remaining ) return $TaskName } $tasksDir = Join-Path $ExtensionPath "tasks" if (!(Test-Path $tasksDir)) { Write-Warning "No tasks directory found at '$tasksDir'" return @() } $tasksToImport = Get-TasksFileListFromExtension -TasksPath $tasksDir $tasksToImport | # Treat tasks with a '_' prefix as private and exclude them Where-Object { !$_.BaseName.StartsWith("_") } | ForEach-Object { $taskItem = $_.FullName Write-Verbose "Importing task '$taskItem'" # This is probably a sign that we should have a different approach for enumerating the # tasks in each extension, but for now we'll just suppress any errors that might occur # when trying to dotsource the file. For example, since this function is running in a # module scope, certain values referenced in the task files may not be available. # Using our private 'task' implementation, we can simply execute each task file and it # will return the name of each task defined in it. $availableTasks += try { . $taskItem } catch {} } } finally { # Undo our Alias manipulation if ($aliasBackup) { New-Alias -Name $aliasBackup.Name -Value $aliasBackup.Definition -Scope Script | Out-Null } } return $availableTasks } |