Psake

psake Build Automation

psake is a PowerShell build automation tool using a DSL for task-based builds with dependencies.

Decision Tree

What kind of build are you creating?

1. PowerShell module → Use PowerShellBuild module (see references/powershell-modules.md)
2. .NET/Node.js/Docker → See references/build-types.md
3. Simple custom build → Continue below for core psake patterns

Build complexity?

• Simple (< 5 tasks, single project) → Use patterns in this file
• Complex (CI/CD, multiple environments, dynamic tasks) → See references/advanced.md

Quick Start

# Install
Install-Module -Name psake -Scope CurrentUser -Force

# Run
Invoke-psake                              # Run 'Default' task
Invoke-psake -taskList Build, Test        # Run specific tasks
Invoke-psake -docs                        # Show task documentation

Minimal psakefile.ps1

Properties {
    $BuildDir = Join-Path $PSScriptRoot 'build'
}

Task Default -depends Build

Task Clean {
    if (Test-Path $BuildDir) { Remove-Item $BuildDir -Recurse -Force }
    New-Item -ItemType Directory -Path $BuildDir -Force | Out-Null
}

Task Build -depends Clean {
    exec { dotnet build -o $BuildDir }
}

Task Test -depends Build {
    exec { dotnet test }
}

Core Commands

Task

Task <name> [-depends <tasks>] [-precondition <scriptblock>] [-description <string>] { <action> }

Task Deploy -depends Build -precondition { $env:CI -eq 'true' } -description "Deploy to prod" {
    exec { ./deploy.ps1 }
}

Properties

Variables that can be overridden via -properties parameter:

Properties {
    $Configuration = 'Release'
    $Version = '1.0.0'
}

Override: Invoke-psake -properties @{ Configuration = 'Debug' }

exec

Runs external commands, fails build on non-zero exit:

exec { dotnet build }                                    # Basic
exec { npm install } "npm install failed"                # Custom error
exec { nuget restore } -maxRetries 3                     # Retry flaky ops
exec { npm test } -workingDirectory './frontend'         # Different directory

Assert

Assert (Test-Path $SrcDir) "Source directory not found"
Assert (-not [string]::IsNullOrEmpty($ApiKey)) "API key required"

Include

Include "./shared/common-tasks.ps1"

FormatTaskName

FormatTaskName "▶ {0}"
# Or with scriptblock:
FormatTaskName { param($taskName) Write-Host "[$taskName]" -ForegroundColor Cyan }

TaskSetup / TaskTearDown

TaskSetup { Write-Host "Starting: $($psake.context.currentTaskName)" }
TaskTearDown { Write-Host "Finished: $($psake.context.currentTaskName)" }

Invoke-psake Parameters

Common Patterns

Conditional Execution

Task Deploy -precondition { $env:GITHUB_REF -eq 'refs/heads/main' } {
    # Only runs on main branch
}

Environment-Specific

Properties {
    $Env = if ($env:ENVIRONMENT) { $env:ENVIRONMENT } else { 'Development' }
}

Task Deploy {
    switch ($Env) {
        'Production' { exec { ./deploy-prod.ps1 } }
        default      { Write-Host "Skipping deploy for $Env" }
    }
}

Multi-Project

Task BuildAll -depends BuildBackend, BuildFrontend

Task BuildBackend {
    Push-Location ./backend
    try { exec { dotnet build } }
    finally { Pop-Location }
}

Task BuildFrontend {
    Push-Location ./frontend
    try { exec { npm run build } }
    finally { Pop-Location }
}

Variable Scoping Between Tasks

Tasks don't share local variables. Use $script: scope to pass data between dependent tasks:

Task GetFiles {
    $script:Files = Get-ChildItem -Path $SrcDir -Filter *.ps1
}

Task ProcessFiles -depends GetFiles {
    foreach ($file in $script:Files) {
        # Process each file
    }
}

Note: psake tasks don't have return values. $script: scoped variables are the recommended approach for task-to-task data sharing.

File Management

psake works for any automation, not just builds:

Task CleanTempFiles {
    $cutoff = (Get-Date).AddDays(-30)
    Get-ChildItem -Path $TempDir -File |
        Where-Object { $_.LastWriteTime -lt $cutoff } |
        Remove-Item -Force
}

Console Output Formatting

For reporting-style tasks:

Task Report {
    Write-Host "Processing: " -NoNewline
    Write-Host $item.Name -ForegroundColor Cyan
    
    $results | Format-Table Name, Size, Age -AutoSize
}

Validating a psakefile

After generating a psakefile, always validate it.

Syntax Check

# Parse without executing - returns errors if invalid
$file = 'psakefile.ps1'
$errors = $null
$null = [System.Management.Automation.Language.Parser]::ParseFile(
    (Resolve-Path $file),
    [ref]$null,
    [ref]$errors
)
if ($errors) {
    $errors | ForEach-Object { Write-Error $_.ToString() }
} else {
    Write-Host "✓ Syntax valid" -ForegroundColor Green
}

Structure Check

Verify the psakefile uses correct psake functions:

$content = Get-Content 'psakefile.ps1' -Raw

# Required elements
$checks = @(
    @{ Name = 'Task definitions'; Pattern = 'Task\s+\w+' }
    @{ Name = 'Properties block'; Pattern = 'Properties\s*\{' }
    @{ Name = 'exec for external commands'; Pattern = 'exec\s*\{' }
)

foreach ($check in $checks) {
    if ($content -match $check.Pattern) {
        Write-Host "✓ $($check.Name)" -ForegroundColor Green
    } else {
        Write-Host "✗ $($check.Name) - not found" -ForegroundColor Yellow
    }
}

Quick Validation One-Liner

pwsh -NoProfile -Command "$e=$null;[void][System.Management.Automation.Language.Parser]::ParseFile('psakefile.ps1',[ref]$null,[ref]$e);if($e){$e}else{'Valid'}"

Troubleshooting

References

• references/powershell-modules.md - PowerShellBuild module for PS module development
• references/build-types.md - .NET, Node.js, Docker build patterns
• references/advanced.md - Dynamic tasks, custom logging, CI/CD integration