Export-MamlCommandHelp doesn't include default value for parameter

[pewill]

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest version
• Search the existing issues.

Steps to reproduce

I try to include parameter default values documentation using PlatyPS but I can't get it to work. It seems like the default values are not populated by New-CommandHelp and even if they are set explicitly on the CommandHelp object or in the markdown file it seems the value is not picked up by Export-MamlCommandHelp and are missing in the generated MAML file.
Repro steps

function Get-Foo {
    param(
        [String] $Name = 'bar'
    )

    "Foo $Name"
}

$cmdHelp = get-command get-foo | New-CommandHelp
$cmdHelp.ToMarkdownString() # note that default value is empty

$cmdHelp.Parameters[0].DefaultValue = "bar" # set the default value explicitly
$cmdHelp.ToMarkdownString() # verify default value is correct
$cmdHelp | Export-MamlCommandHelp -OutputFolder . -force # create maml file. This will not contain the default value
Get-Content .\Get-Foo-Help.xml # notice that there is no <dev:defaultValue>bar</dev:defaultValue> element
Show-HelpPreview -Path .\Get-Foo-Help.xml # notice the missing default value

Expected behavior

NAME
    Get-Foo

SYNOPSIS
    {{ Fill in the Synopsis }}


SYNTAX
    Get-Foo [-Name <System.String>] [<CommonParameters>]


DESCRIPTION
    {{ Fill in the Description }}


PARAMETERS
    -Name [<System.String>]
        {{ Fill Name Description }}

        Required?                    false
        Position?                    0
        Default value                bar
        Accept pipeline input?       false
        Aliases                      none
        Accept wildcard characters?  false

    <CommonParameters>
        This cmdlet supports the common parameters: Verbose, Debug,
        ErrorAction, ErrorVariable, WarningAction, WarningVariable,
        OutBuffer, PipelineVariable, and OutVariable. For more information, see
        about_CommonParameters (https://go.microsoft.com/fwlink/?LinkID=113216).

INPUTS

OUTPUTS
    System.Object
        {{ Fill in the Description }}


NOTES


        {{ Fill in the Notes }}

    --------- Example 1 ---------

    {{ Add example description here }}


RELATED LINKS
    Online Version

Actual behavior

NAME
    Get-Foo

SYNOPSIS
    {{ Fill in the Synopsis }}


SYNTAX
    Get-Foo [-Name <System.String>] [<CommonParameters>]


DESCRIPTION
    {{ Fill in the Description }}


PARAMETERS
    -Name [<System.String>]
        {{ Fill Name Description }}

        Required?                    false
        Position?                    0
        Default value
        Accept pipeline input?       false
        Aliases                      none
        Accept wildcard characters?  false

    <CommonParameters>
        This cmdlet supports the common parameters: Verbose, Debug,
        ErrorAction, ErrorVariable, WarningAction, WarningVariable,
        OutBuffer, PipelineVariable, and OutVariable. For more information, see
        about_CommonParameters (https://go.microsoft.com/fwlink/?LinkID=113216).

INPUTS

OUTPUTS
    System.Object
        {{ Fill in the Description }}


NOTES


        {{ Fill in the Notes }}

    --------- Example 1 ---------

    {{ Add example description here }}


RELATED LINKS
    Online Version

Error details

Environment data

Name                           Value
----                           -----
PSVersion                      7.5.2
PSEdition                      Core
GitCommitId                    7.5.2
OS                             Microsoft Windows 10.0.26100
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Version

1.0.1

Visuals

No response