Built-in `help` function writes Unicode BOM () to host

System Details

• Operating system name and version: Windows 10 Version 1709
• VS Code version: 1.18.0
• PowerShell extension version: 1.5.1
• Output from $PSVersionTable:

Name                           Value
----                           -----
PSVersion                      5.1.16299.64
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.16299.64
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

• VSCode plugin list:

C:\> code --list-extensions --show-versions
bradygaster.azuretoolsforvscode@1.3.0
CoenraadS.bracket-pair-colorizer@0.10.13
DotJoshJohnson.xml@1.9.2
eamodio.gitlens@6.1.0
EditorConfig.EditorConfig@0.11.1
johnpapa.azure-functions-tools@0.3.1
KnisterPeter.vscode-github@0.23.0
ms-mssql.mssql@1.2.1
ms-vscode.azure-account@0.2.2
ms-vscode.csharp@1.13.1
ms-vscode.PowerShell@1.5.1
msazurermtools.azurerm-vscode-tools@0.3.7
patrys.vscode-code-outline@0.0.12
PeterJausovec.vscode-docker@0.0.22
rebornix.Ruby@0.15.0
somekittens.hot-dog-stand@6.6.9
vscodevim.vim@0.10.4
zgudino.editorconfig-vscode-snippet@0.2.0

Issue Description

When I use the help function, a few garbage unicode characters are written to the output stream. Using Get-Help instead of help works as expected. This only happens in the extension-provided Powershell Integrated Console, not the default vscode console.

C:\> help get-date

NAME
    Get-Date
[...snip...]

C:\> help get-date -showwindow


C:\> help get-date > $null
(no output)

C:\> get-help get-date -showwindow
(no output)

On my system, the definition of the help function is:

C:\> Get-Command help | select -ExpandProperty Definition
<#
.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','Workflow','DscResource','Class','Configuration')]
    [string[]]
    ${Category},

    [string[]]
    ${Component},

    [string[]]
    ${Functionality},

    [string[]]
    ${Role},

    [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},

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

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

    #Set the outputencoding to Console::OutputEncoding. More.com doesn't work well with Unicode.
    $outputEncoding=[System.Console]::OutputEncoding

    Get-Help @PSBoundParameters | more

... and more is defined as ...

C:\> Get-Command more | select -ExpandProperty Definition

param([string[]]$paths)
$OutputEncoding = [System.Console]::OutputEncoding
if($paths) {
    foreach ($file in $paths)
    {
        Get-Content $file | more.com
    }
} else { $input | more.com }

Attached Logs

1510862054-d0c22b7a-9fe8-4400-9e12-9cb2d4fd6b5a1510862041231.zip

No source file or test is named. Reproduce the issue in the extension-provided PowerShell Integrated Console with help get-date, then compare Get-Help and the default VS Code console. Trace the help and more entry points and output encoding behavior; done means the BOM is absent while normal output, -showwindow, and redirection still behave as reported.