PSScriptAnalyzer needs a way to handle dot sourced scripts in the context of the parent script

In Plaster, we have separated out user customizable variables and tasks into a file called build.setting.ps1. This file only gets used in a "dot sourced" context from within build.psake.ps1. Because of this, PSSA thinks almost all the variables in the build.settings.ps1 are only being declared but not used later. This results in the following ugliness and worse, may hide the fact that a variable is not actually being used because of the need to suppress the warnings:

Properties {
    # ----------------------- Basic properties --------------------------------

    # The root directories for the module's docs, src and test.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='DocsRootDir')]
    $DocsRootDir = "$PSScriptRoot/docs"
    $SrcRootDir  = "$PSScriptRoot/src"
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='TestRootDir')]
    $TestRootDir = "$PSScriptRoot/test"

    # The name of your module should match the basename of the PSD1 file.
    $ModuleName = Get-Item $SrcRootDir/*.psd1 |
                      Where-Object { $null -ne (Test-ModuleManifest -Path $_ -ErrorAction SilentlyContinue) } |
                      Select-Object -First 1 | Foreach-Object BaseName

    # The $OutDir must match the ModuleName in order to support publishing the module.
    $ReleaseDir = "$PSScriptRoot/Release"
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='OutDir')]
    $OutDir     = "$ReleaseDir/$ModuleName"

    # Default Locale used for documentation generatioon, defaults to en-US.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='DefaultLocale')]
    $DefaultLocale = $null

    # Items in the $Exclude array will not be copied to the $OutDir e.g. $Exclude = @('.gitattributes')
    # Typically you wouldn't put any file under the src dir unless the file was going to ship with
    # the module. However, if there are such files, add their $SrcRootDir relative paths to the exclude list.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='Exclude')]
    $Exclude = @()

    # -------------------- Script analysis properties ------------------------------

    # To control the failure of the build with specific script analyzer rule severities,
    # the CodeAnalysisStop variable can be used. The supported values for this variable are
    # 'Warning', 'Error', 'All', 'None' or 'ReportOnly'. Invalid input will stop on all rules.
    # 'None' will skip over the code analysis step all together.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='ScriptAnalysisAction')]
    $ScriptAnalysisAction = 'Error'

    # Path to PowerShell Script Analyzer settings file.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='ScriptAnalysisSettingsPath')]
    $ScriptAnalysisSettingsPath = "$PSScriptRoot\ScriptAnalyzerSettings.psd1"

    # The script analysis task step will run, unless your host is in the array defined below.
    # This allows you to control whether code analysis is executed, for hosts where script
    # analysis is included in the product.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='SkipScriptAnalysisHost')]
    $SkipScriptAnalysisHost = @(
        'Visual Studio Code Host',
        'My Custom Host with scriptanalyzer support'
    )

    # ------------------- Script signing properties ---------------------------

    # Set to $true if you want to sign your scripts. You will need to have a code-signing certificate.
    # You can specify the certificate's subject name below. If not specified, you will be prompted to
    # provide either a subject name or path to a PFX file.  After this one time prompt, the value will
    # saved for future use and you will no longer be prompted.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='SignScripts')]
    $SignScripts = $false

    # Specify the Subject Name of the certificate used to sign your scripts.  Leave it as $null and the
    # first time you build, you will be prompted to enter your code-signing certificate's Subject Name.
    # This variable is used only if $SignScripts is set to $true.
    #
    # This does require the code-signing certificate to be installed to your certificate store.  If you
    # have a code-signing certificate in a PFX file, install the certificate to your certificate store
    # with the command below. You may be prompted for the certificate's password.
    #
    # Import-PfxCertificate -FilePath .\myCodeSigingCert.pfx -CertStoreLocation Cert:\CurrentUser\My
    #
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='CertSubjectName')]
    $CertSubjectName = $null

    # Certificate store path.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='CertPath')]
    $CertPath = "Cert:\"

    # -------------------- Publishing properties ------------------------------

    # Your NuGet API key for the PSGallery.  Leave it as $null and the first time you publish,
    # you will be prompted to enter your API key.  The build will store the key encrypted in the
    # settings file, so that on subsequent publishes you will no longer be prompted for the API key.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='NuGetApiKey')]
    $NuGetApiKey = $null

    # Name of the repository you wish to publish to. If $null is specified the default repo (PowerShellGallery) is used.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='PublishRepository')]
    $PublishRepository = $null

    # Path to the release notes file.  Set to $null if the release notes reside in the manifest file.
    # The contents of this file are used during publishing for the ReleaseNotes parameter.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='ReleaseNotesPath')]
    $ReleaseNotesPath = "$PSScriptRoot\ReleaseNotes.md"

    # ----------------------- Misc properties ---------------------------------

    # In addition, PFX certificates are supported in an interactive scenario only,
    # as a way to import a certificate into the user personal store for later use.
    # This can be provided using the CertPfxPath parameter. PFX passwords will not be stored.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='SettingsPath')]
    $SettingsPath = "$env:LOCALAPPDATA\Plaster\NewModuleTemplate\SecuredBuildSettings.clixml"

    # The local installation directory for the install task. Defaults to your user PSModulePath.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='InstallPath')]
    $InstallPath = $null

    # Specifies an output file path to send to Invoke-Pester's -OutputFile parameter.
    # This is typically used to write out test results so that they can be sent to a CI
    # system like AppVeyor.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='TestOutputFile')]
    $TestOutputFile = $null

    # Specifies the test output format to use when the TestOutputFile property is given
    # a path.  This parameter is passed through to Invoke-Pester's -OutputFormat parameter.
    [System.Diagnostics.CodeAnalysis.SuppressMessage('PSUseDeclaredVarsMoreThanAssigments', '', Scope='*', Target='TestOutputFormat')]
    $TestOutputFormat = "NUnitXml"
}

It would be nice to be able to tell PSSA that a script file has to be evaluated in the context of another script (the dot sourcing script).

先檢視 issue 中的 dot-sourcing 範例，尤其是 build.psake.ps1 與 build.settings.ps1 之間的關係，並確定 PSScriptAnalyzer 目前如何分析這個獨立的腳本。定義一項設定或進入點，讓分析能夠考量父腳本的內容環境，然後驗證示範的錯誤未使用變數警告已獲得解決，而不會隱藏真正未使用的變數。