Import-Module cmdlet doesn't respect -Verbose:$false switch

You can’t turn off verbose output when importing modules by setting the -Verbose switch’s value to $false.

Steps to reproduce

$VerbosePreference = 'Continue'
Import-Module -Name 'PSDesiredStateConfiguration' -Verbose:$false -Force

Expected behavior

I would expect there to be no verbose output when importing the module.

Actual behavior

I see verbose output:

VERBOSE: Exporting function 'Configuration'.
VERBOSE: Exporting function 'New-DSCCheckSum'.
VERBOSE: Exporting function 'Get-DscResource'.
VERBOSE: Exporting function 'ConvertTo-MOFInstance'.
VERBOSE: Exporting function 'Get-MofInstanceText'.
VERBOSE: Exporting function 'Get-PositionInfo'.
VERBOSE: Exporting function 'Node'.
VERBOSE: Exporting function 'Update-ConfigurationErrorCount'.
VERBOSE: Exporting function 'Get-ConfigurationErrorCount'.
VERBOSE: Exporting function 'Set-PSDefaultConfigurationDocument'.
VERBOSE: Exporting function 'Get-PSDefaultConfigurationDocument'.
VERBOSE: Exporting function 'Get-PSCurrentConfigurationNode'.
VERBOSE: Exporting function 'Set-PSCurrentConfigurationNode'.
VERBOSE: Exporting function 'Set-NodeResources'.
VERBOSE: Exporting function 'Test-NodeResources'.
VERBOSE: Exporting function 'Add-NodeKeys'.
VERBOSE: Exporting function 'Get-InnerMostErrorRecord'.
VERBOSE: Exporting function 'Initialize-ConfigurationRuntimeState'.
VERBOSE: Exporting function 'ValidateUpdate-ConfigurationData'.
VERBOSE: Exporting function 'Test-ModuleReloadRequired'.
VERBOSE: Exporting function 'Configuration'.
VERBOSE: Exporting function 'ImportCimAndScriptKeywordsFromModule'.
VERBOSE: Exporting function 'Write-NodeMOFFile'.
VERBOSE: Exporting function 'ValidateNodeResources'.
VERBOSE: Exporting function 'ValidateNoCircleInNodeResources'.
VERBOSE: Exporting function 'StrongConnect'.
VERBOSE: Exporting function 'Test-MofInstanceText'.
VERBOSE: Exporting function 'Get-EncryptedPassword'.
VERBOSE: Exporting function 'Get-PublicKeyFromStore'.
VERBOSE: Exporting function 'Get-PublicKeyFromFile'.
VERBOSE: Exporting function 'New-DSCCheckSum'.
VERBOSE: Exporting function 'ThrowError'.
VERBOSE: Exporting function 'Write-Log'.
VERBOSE: Exporting function 'WriteFile'.
VERBOSE: Exporting function 'ReadEnvironmentFile'.
VERBOSE: Exporting function 'Get-DscResource'.
VERBOSE: Exporting function 'GetResourceFromKeyword'.
VERBOSE: Exporting function 'GetCompositeResource'.
VERBOSE: Exporting function 'AddDscResourceProperty'.
VERBOSE: Exporting function 'AddDscResourcePropertyFromMetadata'.
VERBOSE: Exporting function 'GetSyntax'.
VERBOSE: Exporting function 'CheckResourceFound'.
VERBOSE: Exporting function 'GetImplementingModulePath'.
VERBOSE: Exporting function 'GetModule'.
VERBOSE: Exporting function 'IsHiddenResource'.
VERBOSE: Exporting function 'GetPatterns'.
VERBOSE: Exporting function 'IsPatternMatched'.
VERBOSE: Exporting alias 'sacfg'.
VERBOSE: Exporting alias 'tcfg'.
VERBOSE: Exporting alias 'gcfg'.
VERBOSE: Exporting alias 'rtcfg'.
VERBOSE: Exporting alias 'glcm'.
VERBOSE: Exporting alias 'slcm'.
VERBOSE: Exporting function 'Get-DscConfiguration'.
VERBOSE: Exporting function 'Test-DscConfiguration'.
VERBOSE: Exporting function 'Get-DscLocalConfigurationManager'.
VERBOSE: Exporting function 'Restore-DscConfiguration'.

Environment data

> $PSVersionTable
                                                   
Name                           Value               
----                           -----               
PSVersion                      4.0                 
WSManStackVersion              3.0                 
SerializationVersion           1.1.0.1             
CLRVersion                     4.0.30319.42000     
BuildVersion                   6.3.9600.16406      
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0}
PSRemotingProtocolVersion      2.2                 

[mklement0]

Tangent alert (may be of interest to some; I’m sharing it, because it baffled me initially):

The processing of -Verbose:$false is somewhat unusual in this case:

Unless you take extra action, passing -SomeSwitch:$false and omitting -SomeSwitch are equivalent. The $SomeSwitch parameter variable will be a [switch]-typed variable whose .IsPresent property (a somewhat unfortunate choice of property name) is $False in both cases.
From what I understand, that is the intent behind -SomeSwitch:$false, which normally only exists to facilitate programmatic construction of a command line.

The only way to distinguish these two cases is to do something like $PSBoundParameters.ContainsKey('SomeSwitch') (or its C# equivalent in a compiled cmdlet), which is apparently what happens here (in PowerShell Core, where this issue’s problem does not happen any longer): $PSBoundParameters.ContainsKey('SomeSwitch') returning $True despite $SomeSwitch.IsPresent returning $False implies that -SomeSwitch:$False was passed.

Thus, -Verbose:$false functioning as a signal to override the $VerbosePreference variable (as opposed to having no effect, which is what seemingly happens in the current production versions) is a semantic anomaly, but it is helpful and documented.

[SteveL-MSFT]

@MaximoTrinidad excellent point, I’ll update the readme