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* Ensure multiply suppressed diagnostics only create one output

* Add extra tests

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Table of Contents


PSScriptAnalyzer is a static code checker for PowerShell modules and scripts. PSScriptAnalyzer checks the quality of PowerShell code by running a set of rules. The rules are based on PowerShell best practices identified by PowerShell Team and the community. It generates DiagnosticResults (errors and warnings) to inform users about potential code defects and suggests possible solutions for improvements.

PSScriptAnalyzer is shipped with a collection of built-in rules that checks various aspects of PowerShell code such as presence of uninitialized variables, usage of PSCredential Type, usage of Invoke-Expression etc. Additional functionalities such as exclude/include specific rules are also supported.

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Get-ScriptAnalyzerRule [-CustomRulePath <String[]>] [-RecurseCustomRulePath] [-Name <String[]>] [-Severity <String[]>] [<CommonParameters>]

Invoke-ScriptAnalyzer [-Path] <String> [-CustomRulePath <String[]>] [-RecurseCustomRulePath] [-ExcludeRule <String[]>] [-IncludeDefaultRules] [-IncludeRule <String[]>] [-Severity <String[]>] [-Recurse] [-SuppressedOnly] [-Fix] [-EnableExit] [-ReportSummary] [-Settings <Object>] [-SaveDscDependency] [<CommonParameters>]

Invoke-ScriptAnalyzer [-ScriptDefinition] <String> [-CustomRulePath <String[]>] [-RecurseCustomRulePath] [-ExcludeRule <String[]>] [-IncludeDefaultRules] [-IncludeRule <String[]>] [-Severity <String[]>] [-Recurse] [-SuppressedOnly] [-EnableExit] [-ReportSummary] [-Settings <Object>] [-SaveDscDependency] [<CommonParameters>]

Invoke-Formatter [-ScriptDefinition] <String> [[-Settings] <Object>] [[-Range] <Int32[]>] [<CommonParameters>]

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From PowerShell Gallery

Install-Module -Name PSScriptAnalyzer

Note: For PowerShell version 5.1.14393.206 or newer, before installing PSScriptAnalyzer, please install the latest Nuget provider by running the following in an elevated PowerShell session.

Install-PackageProvider Nuget -MinimumVersion –Force

Supported PowerShell Versions and Platforms

  • Windows PowerShell 3.0 or greater
  • PowerShell Core 7.0.3 or greater on Windows/Linux/macOS
  • Docker (tested only using Docker Desktop on Windows 10 1809)
    • PowerShell 6 Windows Image tags from Example (1 warning gets produced by Save-Module but can be ignored):

      docker run -it pwsh -command "Save-Module -Name PSScriptAnalyzer -Path .; Import-Module .\PSScriptAnalyzer; Invoke-ScriptAnalyzer -ScriptDefinition 'gci'"

    • PowerShell 5.1 (Windows): Only the images work but not the microsoft/nanoserver images because they contain a Core version of it. Example:

      docker run -it powershell -command "Install-PackageProvider -Name NuGet -MinimumVersion -Force; Install-Module PSScriptAnalyzer -Force; Invoke-ScriptAnalyzer -ScriptDefinition 'gci'"

    • Linux tags from - Example:

      docker run -it pwsh -c "Install-Module PSScriptAnalyzer -Force; Invoke-ScriptAnalyzer -ScriptDefinition 'gci'"

From Chocolatey

If you prefer to manage PSScriptAnalyzer as a Windows package, you can use Chocolatey to install it.

If you don't have Chocolatey, you can install it from the Chocolately Install page. With Chocolatey installed, execute the following command to install PSScriptAnalyzer:

choco install psscriptanalyzer

Note: the PSScriptAnalyzer Chocolatey package is provided and supported by the community.

From Source



  • Obtain the source

    • Download the latest source code from the release page OR
    • Clone the repository (needs git)
    git clone
  • Navigate to the source directory

    cd path/to/PSScriptAnalyzer
  • Building

    You can either build using the Visual Studio solution PSScriptAnalyzer.sln or build using PowerShell specifically for your platform as follows:

    • The default build is for the currently used version of PowerShell
    • Windows PowerShell version 5.0
    .\build.ps1 -PSVersion 5
    • Windows PowerShell version 4.0
    .\build.ps1 -PSVersion 4
    • Windows PowerShell version 3.0
    .\build.ps1 -PSVersion 3
    • PowerShell 7
    .\build.ps1 -PSVersion 7
  • Rebuild documentation since it gets built automatically only the first time

    .\build.ps1 -Documentation
  • Build all versions (PowerShell v3, v4, v5, and v6) and documentation

    .\build.ps1 -All
  • Import the module

Import-Module .\out\PSScriptAnalyzer\PSScriptAnalyzer.psd1

To confirm installation: run Get-ScriptAnalyzerRule in the PowerShell console to obtain the built-in rules

  • Adding/Removing resource strings

For adding/removing resource strings in the *.resx files, it is recommended to use Visual Studio since it automatically updates the strongly typed *.Designer.cs files. The Visual Studio 2017 Community Edition is free to use but should you not have/want to use Visual Studio then you can either manually adapt the *.Designer.cs files or use the New-StronglyTypedCsFileForResx.ps1 script although the latter is discouraged since it leads to a bad diff of the *.Designer.cs files.


Pester-based ScriptAnalyzer Tests are located in path/to/PSScriptAnalyzer/Tests folder.

  • Ensure Pester 4.3.1 or higher is installed
  • In the root folder of your local repository, run:
./build -Test

To retrieve the results of the run, you can use the tools which are part of the build module (build.psm1)

Import-Module ./build.psm1

To retrieve only the errors, you can use the following:

Import-Module ./build.psm1

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Parser Errors

In prior versions of ScriptAnalyer, errors found during parsing were reported as errors and diagnostic records were not created. ScriptAnalyzer now emits parser errors as diagnostic records in the output stream with other diagnostic records.

PS> Invoke-ScriptAnalyzer -ScriptDefinition '"b" = "b"; function eliminate-file () { }'

RuleName            Severity   ScriptName Line Message
--------            --------   ---------- ---- -------
InvalidLeftHandSide ParseError            1    The assignment expression is not
                                               valid. The input to an
                                               assignment operator must be an
                                               object that is able to accept
                                               assignments, such as a variable
                                               or a property.
PSUseApprovedVerbs  Warning               1    The cmdlet 'eliminate-file' uses an
                                               unapproved verb.

The RuleName is set to the ErrorId of the parser error.

If ParseErrors would like to be suppressed, do not include it as a value in the -Severity parameter.

PS> Invoke-ScriptAnalyzer -ScriptDefinition '"b" = "b"; function eliminate-file () { }' -Severity Warning

RuleName           Severity ScriptName Line Message
--------           -------- ---------- ---- -------
PSUseApprovedVerbs Warning             1    The cmdlet 'eliminate-file' uses an
                                            unapproved verb.

Suppressing Rules

You can suppress a rule by decorating a script/function or script/function parameter with .NET's SuppressMessageAttribute. SuppressMessageAttribute's constructor takes two parameters: a category and a check ID. Set the categoryID parameter to the name of the rule you want to suppress and set the checkID parameter to a null or empty string. You can optionally add a third named parameter with a justification for suppressing the message:

function SuppressMe()
    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSProvideCommentHelp', '', Justification='Just an example')]

    Write-Verbose -Message "I'm making a difference!"


All rule violations within the scope of the script/function/parameter you decorate will be suppressed.

To suppress a message on a specific parameter, set the SuppressMessageAttribute's CheckId parameter to the name of the parameter:

function SuppressTwoVariables()
    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSProvideDefaultParameterValue', 'b')]
    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSProvideDefaultParameterValue', 'a')]
    param([string]$a, [int]$b)

Use the SuppressMessageAttribute's Scope property to limit rule suppression to functions or classes within the attribute's scope.

Use the value Function to suppress violations on all functions within the attribute's scope. Use the value Class to suppress violations on all classes within the attribute's scope:

[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSProvideCommentHelp', '', Scope='Function')]

function InternalFunction

    Write-Verbose -Message "I am invincible!"

You can further restrict suppression based on a function/parameter/class/variable/object's name by setting the SuppressMessageAttribute's Target property to a regular expression or a glob pattern. Few examples are given below.

Suppress PSAvoidUsingWriteHost rule violation in start-bar and start-baz but not in start-foo and start-bam:

[System.Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingWriteHost', '', Scope='Function', Target='start-ba[rz]')]
function start-foo {
    write-host "start-foo"

function start-bar {
    write-host "start-bar"

function start-baz {
    write-host "start-baz"

function start-bam {
    write-host "start-bam"

Suppress violations in all the functions:

[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingWriteHost', '', Scope='Function', Target='*')]

Suppress violation in start-bar, start-baz and start-bam but not in start-foo:

[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingWriteHost', '', Scope='Function', Target='start-b*')]

Note: Parser Errors cannot be suppressed via the SuppressMessageAttribute

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Settings Support in ScriptAnalyzer

Settings that describe ScriptAnalyzer rules to include/exclude based on Severity can be created and supplied to Invoke-ScriptAnalyzer using the Setting parameter. This enables a user to create a custom configuration for a specific environment. We support the following modes for specifying the settings file.

Using parameter Settings

Built-in Presets

ScriptAnalyzer ships a set of built-in presets that can be used to analyze scripts. For example, if the user wants to run PowerShell Gallery rules on their module, then they use the following command.

PS> Invoke-ScriptAnalyzer -Path /path/to/module/ -Settings PSGallery -Recurse

Along with PSGallery there are a few other built-in presets, including, DSC and CodeFormatting, that can be used. These presets can be tab completed for the Settings parameter.


The following example excludes two rules from the default set of rules and any rule that does not output an Error or Warning diagnostic record.

# PSScriptAnalyzerSettings.psd1

Then invoke that settings file when using Invoke-ScriptAnalyzer:

Invoke-ScriptAnalyzer -Path MyScript.ps1 -Settings PSScriptAnalyzerSettings.psd1

The next example selects a few rules to execute instead of all the default rules.

# PSScriptAnalyzerSettings.psd1

Then invoke that settings file:

Invoke-ScriptAnalyzer -Path MyScript.ps1 -Settings PSScriptAnalyzerSettings.psd1


If you place a PSScriptAnayzer settings file named PSScriptAnalyzerSettings.psd1 in your project root, PSScriptAnalyzer will discover it if you pass the project root as the Path parameter.

Invoke-ScriptAnalyzer -Path "C:\path\to\project" -Recurse

Note that providing settings explicitly takes higher precedence over this implicit mode. Sample settings files are provided here.

Custom rules

It is possible to provide one or more paths to custom rules in the settings file. It is important that these paths either point to a module's folder (implicitly uses the module manifest) or to the module's script file (.psm1). The module should export the custom rules (as functions) for them to be available to PS Script Analyzer.

In this example the property CustomRulePath points to two different modules. Both modules exports the rules (the functions) with the verb Measure so that is used for the property IncludeRules.

    CustomRulePath      = @(

    IncludeRules        = @(

It is also possible to used default rules by adding those to IncludeRules. When including default rules is important that the property IncludeDefaultRules is set to $true otherwise the default rules will not be triggered.

    CustomRulePath      = @(

    IncludeDefaultRules = $true

    IncludeRules        = @(
        # Default rules

        # Custom rules

Using custom rules in Visual Studio Code

It is also possible to use the custom rules that are provided in the settings file in Visual Studio Code. This is done by adding a Visual Studio Code workspace settings file (.vscode/settings.json).

    "powershell.scriptAnalysis.settingsPath": ".vscode\\analyzersettings.psd1",
    "powershell.scriptAnalysis.enable": true,

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ScriptAnalyzer as a .NET library

ScriptAnalyzer engine and functionality can now be directly consumed as a library.

Here are the public interfaces:

using Microsoft.Windows.PowerShell.ScriptAnalyzer;

public void Initialize(System.Management.Automation.Runspaces.Runspace runspace,
Microsoft.Windows.PowerShell.ScriptAnalyzer.IOutputWriter outputWriter,
[string[] customizedRulePath = null],
[string[] includeRuleNames = null],
[string[] excludeRuleNames = null],
[string[] severity = null],
[bool suppressedOnly = false],
[string profile = null])

public System.Collections.Generic.IEnumerable<DiagnosticRecord> AnalyzePath(string path,
    [bool searchRecursively = false])

public System.Collections.Generic.IEnumerable<IRule> GetRule(string[] moduleNames, string[] ruleNames)

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Violation Correction

Some violations can be fixed by replacing the violation causing content with a suggested alternative. You can use the -Fix switch to automatically apply the suggestions. Since Invoke-ScriptAnalyzer implements SupportsShouldProcess, you can additionally use -WhatIf or -Confirm to find out which corrections would be applied. It goes without saying that you should use source control when applying those corrections since some some of them such as the one for AvoidUsingPlainTextForPassword might require additional script modifications that cannot be made automatically. Should your scripts be sensitive to encoding you should also check that because the initial encoding can not be preserved in all cases.

The initial motivation behind having the SuggestedCorrections property on the ErrorRecord (which is how the -Fix switch works under the hood) was to enable quick-fix like scenarios in editors like VSCode, Sublime, etc. At present, we provide valid SuggestedCorrection only for the following rules, while gradually adding this feature to more rules.

  • AvoidAlias.cs
  • AvoidUsingPlainTextForPassword.cs
  • MisleadingBacktick.cs
  • MissingModuleManifestField.cs
  • UseToExportFieldsInManifest.cs

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Contributions are welcome

There are many ways to contribute:

  1. Open a new bug report, feature request or just ask a question by opening a new issue here.
  2. Participate in the discussions of issues, pull requests and verify/test fixes or new features.
  3. Submit your own fixes or features as a pull request but please discuss it beforehand in an issue if the change is substantial.
  4. Submit test cases.

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Creating a Release

  • Update changelog ( with the new version number and change set. When updating the changelog please follow the same pattern as that of previous change sets (otherwise this may break the next step).
  • Import the ReleaseMaker module and execute New-Release cmdlet to perform the following actions.
    • Update module manifest (engine/PSScriptAnalyzer.psd1) with the new version number and change set
    • Update the version number in Engine/Engine.csproj and Rules/Rules.csproj
    • Create a release build in out/
    PS> Import-Module .\Utils\ReleaseMaker.psm1
    PS> New-Release
  • Sign the binaries and PowerShell files in the release build and publish the module to PowerShell Gallery.
  • Draft a new release on github and tag master with the new version number.

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Code of Conduct

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.

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