Reduce PowerShell Lambda INIT time by omitting unwanted files from packaged modules (#2358)

Author: sankettangade

CHANGELOG.md

@@ -1,3 +1,8 @@
+## Release 2026-05-30
+
+### AWSLambdaPSCore PowerShell Module (5.0.2)
+* Reduce Lambda cold start INIT times by stripping files that are not used at runtime (PowerShell help XML and .pdb debug symbols) from AWS-authored modules (AWSPowerShell.NetCore and AWS.Tools.*) during packaging
+
 ## Release 2026-05-28
 
 ### Amazon.Lambda.RuntimeSupport (2.1.1)

PowerShell/Module/AWSLambdaPSCore.psd1

@@ -12,7 +12,7 @@
 RootModule = 'AWSLambdaPSCore.psm1'
 
 # Version number of this module.
-ModuleVersion = '5.0.1.0'
+ModuleVersion = '5.0.2.0'
 
 # Supported PSEditions
 CompatiblePSEditions = 'Core'

PowerShell/Module/Private/_Constants.ps1

@@ -31,4 +31,33 @@ if (!($AwsPowerShellTargetFramework))
 if (!($AwsPowerShellLambdaRuntime))
 {
     New-Variable -Name AwsPowerShellLambdaRuntime -Value 'dotnet10' -Option Constant
+}
+
+if (!($AwsModuleStripFilters))
+{
+    # File patterns inside AWS-authored PowerShell modules that have no purpose at
+    # Lambda runtime (no interactive shell, no Get-Help, no debugger). Stripping
+    # them reduces package size and INIT (cold-start) duration. LICENSE / NOTICE
+    # files are intentionally retained.
+    #
+    # The '*.xml' pattern matches case-insensitively, covering:
+    #   - <Module>.dll-Help.xml — PowerShell MAML help
+    #   - <Module>.XML          — .NET XMLDoc compiler output (IntelliSense data)
+    #   - PSGetModuleInfo.xml   — PowerShellGet install metadata
+    # Format.ps1xml / Types.ps1xml are NOT matched because their extension is
+    # .ps1xml (not .xml) and the wildcard requires a literal '.xml' suffix.
+    New-Variable -Name AwsModuleStripFilters -Value @(
+        '*.xml',
+        '*.pdb'
+    ) -Option Constant
+}
+
+if (!($AwsAuthoredModuleNamePatterns))
+{
+    # Only AWS-authored modules under Modules/ are stripped; third-party / community
+    # modules are left untouched.
+    New-Variable -Name AwsAuthoredModuleNamePatterns -Value @(
+        'AWSPowerShell.NetCore',
+        'AWS.Tools.*'
+    ) -Option Constant
 }

PowerShell/Module/Private/_DeploymentFunctions.ps1

@@ -479,6 +479,57 @@ function _formatArray
     return $sb.ToString()
 }
 
+function _stripAwsModuleFiles
+{
+    param
+    (
+        [Parameter(Mandatory = $true)]
+        [string]$ModulesRoot,
+
+        [Parameter(Mandatory = $true)]
+        [string[]]$Filters,
+
+        [Parameter(Mandatory = $true)]
+        [string[]]$ModuleNamePatterns
+    )
+
+    if (!(Test-Path -Path $ModulesRoot))
+    {
+        return
+    }
+
+    foreach ($moduleDir in (Get-ChildItem -Path $ModulesRoot -Directory))
+    {
+        $matchesAws = $false
+        foreach ($pattern in $ModuleNamePatterns)
+        {
+            if ($moduleDir.Name -like $pattern)
+            {
+                $matchesAws = $true
+                break
+            }
+        }
+
+        if (-not $matchesAws)
+        {
+            continue
+        }
+
+        $removed = Get-ChildItem -Path $moduleDir.FullName -Recurse -File -Include $Filters -ErrorAction SilentlyContinue
+        foreach ($file in $removed)
+        {
+            Write-Verbose ('Removing AWS module file: {0}' -f $file.FullName)
+            Remove-Item -LiteralPath $file.FullName -Force -ErrorAction SilentlyContinue
+        }
+
+        $count = ($removed | Measure-Object).Count
+        if ($count -gt 0)
+        {
+            Write-Verbose ('Stripped {0} unwanted file(s) from AWS module {1}' -f $count, $moduleDir.Name)
+        }
+    }
+}
+
 function _prepareDependentPowerShellModules
 {
     param
@@ -567,6 +618,11 @@ function _prepareDependentPowerShellModules
     }
     ## Add verbosity that no RequiredModules found
     else {Write-Verbose "No RequiredModules found for script '$Script'"}
+
+    _stripAwsModuleFiles `
+        -ModulesRoot $SavedModulesDirectory `
+        -Filters $AwsModuleStripFilters `
+        -ModuleNamePatterns $AwsAuthoredModuleNamePatterns
 }
 
 function _findLocalModule

PowerShell/Tests/Get-AWSPowerShelLambdaTemplate.Tests.ps1

@@ -7,31 +7,33 @@ Import-Module $moduleManifestPath
 InModuleScope -ModuleName $module -ScriptBlock {
     Describe -Name 'Get-AWSPowerShellLambdaTemplate' -Fixture {
 
-        function LoadFakeData
-        {
-            ConvertTo-Json -InputObject @{
-                manifestVersion = 1
-                blueprints      = @(
-                    @{
-                        name        = 'Basic'
-                        description = 'Bare bones script'
-                        content     = @(
-                            @{
-                                source   = 'basic.ps1.txt'
-                                output   = '{basename}.ps1'
-                                filetype = 'lambdaFunction'
-                            },
-                            @{
-                                source = 'readme.txt'
-                                output = 'readme.txt'
-                            }
-                        )
-                    }
-                )
+        BeforeAll {
+            function LoadFakeData
+            {
+                ConvertTo-Json -InputObject @{
+                    manifestVersion = 1
+                    blueprints      = @(
+                        @{
+                            name        = 'Basic'
+                            description = 'Bare bones script'
+                            content     = @(
+                                @{
+                                    source   = 'basic.ps1.txt'
+                                    output   = '{basename}.ps1'
+                                    filetype = 'lambdaFunction'
+                                },
+                                @{
+                                    source = 'readme.txt'
+                                    output = 'readme.txt'
+                                }
+                            )
+                        }
+                    )
+                }
             }
+            Mock -CommandName '_getHostedBlueprintsContent' -MockWith {LoadFakeData}
+            Mock -CommandName '_getLocalBlueprintsContent' -MockWith {LoadFakeData}
         }
-        Mock -CommandName '_getHostedBlueprintsContent' -MockWith {LoadFakeData}
-        Mock -CommandName '_getLocalBlueprintsContent' -MockWith {LoadFakeData}
 
         Context -Name 'Online Templates' -Fixture {
             It -Name 'Retrieves Blueprints from online sources by default' -Test {