"help" command triggers an error

[EricBuist]

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest released version
• Search the existing issues.
• Refer to the FAQ.
• Refer to Differences between Windows PowerShell 5.1 and PowerShell.

Steps to reproduce

In Powershell Core 7.2.1 on Windows 10, type "help" command and press enter.

Expected behavior

The "help" command should display information about how to use Powershell.

Actual behavior

The command displays the following error message.

InvalidOperation:
Line |
 124 |              $consoleWidth = [System.Math]::Max([System.Console]::Wind …
     |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | Cannot invoke method. Method invocation is supported only on core types in this language mode.
Out-String:
Line |
 139 |  …         $help | Out-String -Stream -Width ($consoleWidth - 1) | & $pa …
     |                                              ~~~~~~~~~~~~~~~~~~~
     | Cannot validate argument on parameter 'Width'. The -1 argument is less than the minimum allowed range of 2. Supply an argument that is greater than or equal to 2 and then try the command again.

Error details

No response

Environment data

Powershell Core 7.2.1
Windows 10 21H2

Visuals

No response

[237dmitry]

what is $help variable?

The "help" command should display information about how to use Powershell.

help command is alias for Get-Help cmdlet and without arguments shows common information how to use help system.

[vexx32]

It's not an alias, it's a built in function. So that code must be internal to the function.

From the error, it looks like you're running in constrained language mode. You'll probably need to use Get-Help rather than the builtin help function in that mode.

[jhoneill]

Method invocation is supported only on core types in this language mode.

That message normally means you have put PowerShell into a restricted language mode.
I couldn't repro the error even if select restricted (or no) language.

How are you starting PowerShell. If you just run pwsh -noProfile do you get the same error ? And what does
$ExecutionContext.SessionState.LanguageMode report ?

[237dmitry]

It's not an alias, it's a built in function.

I've always been sure that this is an alias. Very similar to the proxy function for Get-Help:

> gc function:help

<#
.FORWARDHELPTARGETNAME Get-Help
.FORWARDHELPCATEGORY Cmdlet
#>

> [Management.Automation.ProxyCommand]::Create((Get-Command Get-Help))

<#
.ForwardHelpTargetName Microsoft.PowerShell.Core\Get-Help
.ForwardHelpCategory Cmdlet
#>

[vexx32]

This is what I have by default for Get-Content function:help. It's not a simple proxy function, it does additional handling for pagers and a few other things.

Expand for code

<#
.FORWARDHELPTARGETNAME Get-Help
.FORWARDHELPCATEGORY Cmdlet
#>
[CmdletBinding(DefaultParameterSetName='AllUsersView', HelpUri='https://go.microsoft.com/fwlink/?LinkID=113316')]
param(
    [Parameter(Position=0, ValueFromPipelineByPropertyName=$true)]
    [string]
    ${Name},

    [string]
    ${Path},

    [ValidateSet('Alias','Cmdlet','Provider','General','FAQ','Glossary','HelpFile','ScriptCommand','Function','Filter','ExternalScript','All','DefaultHelp','DscResource','Class','Configuration')]
    [string[]]
    ${Category},

    [Parameter(ParameterSetName='DetailedView', Mandatory=$true)]
    [switch]
    ${Detailed},

    [Parameter(ParameterSetName='AllUsersView')]
    [switch]
    ${Full},

    [Parameter(ParameterSetName='Examples', Mandatory=$true)]
    [switch]
    ${Examples},

    [Parameter(ParameterSetName='Parameters', Mandatory=$true)]
    [string[]]
    ${Parameter},

    [string[]]
    ${Component},

    [string[]]
    ${Functionality},

    [string[]]
    ${Role},

    [Parameter(ParameterSetName='Online', Mandatory=$true)]
    [switch]
    ${Online},

    [Parameter(ParameterSetName='ShowWindow', Mandatory=$true)]
    [switch]
    ${ShowWindow})

    # Display the full help topic by default but only for the AllUsersView parameter set.
    if (($psCmdlet.ParameterSetName -eq 'AllUsersView') -and !$Full) {
        $PSBoundParameters['Full'] = $true
    }

    # Nano needs to use Unicode, but Windows and Linux need the default
    $OutputEncoding = if ([System.Management.Automation.Platform]::IsNanoServer -or [System.Management.Automation.Platform]::IsIoT) {
        [System.Text.Encoding]::Unicode
    } else {
        [System.Console]::OutputEncoding
    }

    $help = Get-Help @PSBoundParameters

    # If a list of help is returned or AliasHelpInfo (because it is small), don't pipe to more
    $psTypeNames = ($help | Select-Object -First 1).PSTypeNames
    if ($psTypeNames -Contains 'HelpInfoShort' -Or $psTypeNames -Contains 'AliasHelpInfo')
    {
        $help
    }
    elseif ($help -ne $null)
    {
        # By default use more on Windows and less on Linux.
        if ($IsWindows) {
            $pagerCommand = 'more.com'
            $pagerArgs = $null
        }
        else {
            $pagerCommand = 'less'
            # PSNativeCommandArgumentPassing arguments should be constructed differently.
            if ($EnabledExperimentalFeatures -contains 'PSNativeCommandArgumentPassing') {
                $pagerArgs = '-s','-P','Page %db?B of %D:.\. Press h for help or q to quit\.'
            }
            else {
                $pagerArgs = '-Ps"Page %db?B of %D:.\. Press h for help or q to quit\.$"'
            }
        }

        # Respect PAGER environment variable which allows user to specify a custom pager.
        # Ignore a pure whitespace PAGER value as that would cause the tokenizer to return 0 tokens.
        if (![string]::IsNullOrWhitespace($env:PAGER)) {
            if (Get-Command $env:PAGER -ErrorAction Ignore) {
                # Entire PAGER value corresponds to a single command.
                $pagerCommand = $env:PAGER
                $pagerArgs = $null
            }
            else {
                # PAGER value is not a valid command, check if PAGER command and arguments have been specified.
                # Tokenize the specified $env:PAGER value. Ignore tokenizing errors since any errors may be valid
                # argument syntax for the paging utility.
                $errs = $null
                $tokens = [System.Management.Automation.PSParser]::Tokenize($env:PAGER, [ref]$errs)

                $customPagerCommand = $tokens[0].Content
                if (!(Get-Command $customPagerCommand -ErrorAction Ignore)) {
                    # Custom pager command is invalid, issue a warning.
                    Write-Warning "Custom-paging utility command not found. Ignoring command specified in `$env:PAGER: $env:PAGER"
                }
                else {
                    # This approach will preserve all the pagers args.
                    $pagerCommand = $customPagerCommand
                    $pagerArgs = if ($tokens.Count -gt 1) {$env:PAGER.Substring($tokens[1].Start)} else {$null}
                }
            }
        }

        $pagerCommandInfo = Get-Command -Name $pagerCommand -ErrorAction Ignore
        if ($pagerCommandInfo -eq $null) {
            $help
        }
        elseif ($pagerCommandInfo.CommandType -eq 'Application') {
            # If the pager is an application, format the output width before sending to the app.
            $consoleWidth = [System.Math]::Max([System.Console]::WindowWidth, 20)

            if ($pagerArgs) {
                # Start the pager arguments directly if the PSNativeCommandArgumentPassing feature is enabled.
                # Otherwise, supply pager arguments to an application without any PowerShell parsing of the arguments.
                # Leave environment variable to help user debug arguments supplied in $env:PAGER.
                if ($EnabledExperimentalFeatures -contains 'PSNativeCommandArgumentPassing') {
                    $help | Out-String -Stream -Width ($consoleWidth - 1) | & $pagerCommand $pagerArgs
                }
                else {
                    $env:__PSPAGER_ARGS = $pagerArgs
                    $help | Out-String -Stream -Width ($consoleWidth - 1) | & $pagerCommand --% %__PSPAGER_ARGS%
                }
            }
            else {
                $help | Out-String -Stream -Width ($consoleWidth - 1) | & $pagerCommand
            }
        }
        else {
            # The pager command is a PowerShell function, script or alias, so pipe directly into it.
            $help | & $pagerCommand $pagerArgs
        }
    }

[237dmitry]

I have so. I did not paste full output. I can't figure out what is causing the error in:

$consoleWidth = [System.Math]::Max([System.Console]::WindowWidth, 20)

[System.Math] is not a core type?

[vexx32]

"Core type" just means "it's not one of the pre-approved types defined by the Restricted Language mode". Offhand I'm not sure what they are, but it's likely just PSObject and a scant handful of others.

Restricted Language mode is pretty much by design useless.

[EricBuist]

Hi, I tried get-help and it works correctly. The "help" command, however, shows the error message.

[iSazonov]

GetHelpPagingFunctionText() creates the function in InitialSessionState so we could set-restore LanguageMode.

[SeeminglyScience]

The Engine WG reviewed this today. We agree that this function should either work the same in CLM or at the very least emit a better error message. We're marking this as up for grabs.

[CarloToso]

I tested this issue in Powershell 7.2.7
$ExecutionContext.SessionState.LanguageMode = "ConstrainedLanguage"
help
Get-Help

Both commands worked correctly, no errors

[kvprasoon]

@iSazonov Looks like this can be closed

[EricBuist]

This issue does not occur anymore. I searched endlessly and cannot find a way to close it. Why can't the issue creator close it?

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if there is no further activity in 7 days, the issue will be closed automatically.

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