Create-DefaultListForms.ps1

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<#
  .SYNOPSIS
  Script to create default list forms (New, Edit, Display) if they are missing.
  Will also re-add missing Form Webpart to existing list forms if they are missing.
  Expects a CSV file called TargetListForms.csv to be in the same directory as the script.
  CSV should have a siteUrl and listTitle columns.

 .DESCRIPTION
  Script to create default list forms (New, Edit, Display) if they are missing.
  Will also re-add missing Form Webpart to existing list forms if they are missing.
  Expects a CSV file called TargetListForms.csv to be in the same directory as the script.
  CSV should have a siteUrl and listTitle columns.

  Tested with List Templates: 100, 101, 102, 103, 104, 105, 106, 107, 108

  NOTE: This script requires the PowerShell module 'SharePointPnPPowerShellOnline' to be installed. If it is missing, the script will attempt to install it.

  RECOMMENDATION: Add administrator username and password for your tenant to Windows Credential Manager before running script.
  https://github.com/SharePoint/PnP-PowerShell/wiki/How-to-use-the-Windows-Credential-Manager-to-ease-authentication-with-PnP-PowerShell

  .PARAMETER CSVPath
  Specify the path to a CSV file containing siteUrl and listTitle fields.

  .PARAMETER UseWebLogin
  Login via web browser

 .EXAMPLE
  .\Create-DefaultListForms.ps1

  Creates list forms for specified siteUrl and listTitle rows in a CSV file in the script directory called Create-DefaultListForms-Sample.csv

 .EXAMPLE
  .\Create-DefaultListForms.ps1 -CSVPath C:\temp\targetlists.csv

  Creates list forms for specified siteUrl and listTitle rows in a CSV file located at C:\temp\targetlists.csv

 .EXAMPLE
  .\Create-DefaultListForms.ps1 -CSVPath C:\temp\targetlists.csv -UseWebLogin

  Creates list forms for specified siteUrl and listTitle rows in a CSV file located at C:\temp\targetlists.csv, using the browser for login
#>

param(
    $CSVPath = "$(Split-Path -Parent -Path $MyInvocation.MyCommand.Definition)\Create-DefaultListForms-Sample.csv",
    [switch]$UseWebLogin
    )

#############################################

$module = Get-Module SharePointPnPPowerShellOnline -ListAvailable
if ($null -eq $module) {
    Write-Output "Installing PowerShell Module: SharePointPnPPowerShellOnline"
    Install-Module SharePointPnPPowerShellOnline -Force -AllowClobber -Confirm:$false
}

#############################################

$webpartTemplate = @"
<WebPart xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/WebPart/v2">
    <Assembly>Microsoft.SharePoint, Version=16.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c</Assembly>
    <TypeName>Microsoft.SharePoint.WebPartPages.ListFormWebPart</TypeName>
    <ListName xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">{{{LIST_ID}}}</ListName>
    <ListId xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">{{LIST_ID}}</ListId>
    <PageType xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">{{PAGE_TYPE}}</PageType>
    <FormType xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">{{FORM_TYPE}}</FormType>
    <ControlMode xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">{{CONTROL_MODE}}</ControlMode>
    <ViewFlag xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">1048576</ViewFlag>
    <ViewFlags xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">Default</ViewFlags>
    <ListItemId xmlns="http://schemas.microsoft.com/WebPart/v2/ListForm">0</ListItemId>
</WebPart>
"@

Function Create-DefaultListForm
{
    param(
        [parameter(Mandatory=$true)]$List,
        [parameter(Mandatory=$true)][string]$FormUrl,
        [parameter(Mandatory=$true)][ValidateSet("Display", "Edit", "New")]$FormType
    )

    begin { }
    process
    {

        $webpartXml = $webpartTemplate -replace "{{LIST_ID}}", $List.Id.ToString()

        switch ($FormType)
        {
            "Display" {
                $webpartXml = $webpartXml -replace "{{PAGE_TYPE}}", "PAGE_DISPLAYFORM"
                $webpartXml = $webpartXml -replace "{{FORM_TYPE}}", "4"
                $webpartXml = $webpartXml -replace "{{CONTROL_MODE}}", "Display"
                break;
            }
            "Edit" {
                $webpartXml = $webpartXml -replace "{{PAGE_TYPE}}", "PAGE_EDITFORM"
                $webpartXml = $webpartXml -replace "{{FORM_TYPE}}", "6"
                $webpartXml = $webpartXml -replace "{{CONTROL_MODE}}", "Edit"
                break;
            }
            "New" {
                $webpartXml = $webpartXml -replace "{{PAGE_TYPE}}", "PAGE_NEWFORM"
                $webpartXml = $webpartXml -replace "{{FORM_TYPE}}", "8"
                $webpartXml = $webpartXml -replace "{{CONTROL_MODE}}", "New"
                break;
            }
        }

        try
        {
            #Check if form page already exists
            $listPages = Get-PnPProperty -ClientObject $List.RootFolder -Property Files
            $formPage = $listPages | Where-Object { $_.ServerRelativeUrl.ToLower() -eq $FormUrl.ToLower() }

            if ($null -eq $formPage) {
                Write-Output "  [Creating Form Page] $FormUrl"

                #Create Form
                $formPage = $List.RootFolder.Files.AddTemplateFile($FormUrl, [Microsoft.SharePoint.Client.TemplateFileType]::FormPage)
            }
            else {
                #Form page exists, check if form is recognized by list (i.e. form page has a form webpart on it)
                $listForms = Get-PnPProperty -ClientObject $List -Property Forms

                if ($null -ne $listForms -and $listForms.Count -gt 0) {
                    $existingForm = $list.Forms | Where-Object { $_.ServerRelativeUrl.ToLower() -eq $FormUrl.ToLower() }
                    if ($null -ne $existingForm) {
                        Write-Warning "  [Form Already Exists] $FormUrl"
                        return;
                    }
                }
            }

            Write-Output "  [Adding Form Webpart] $FormUrl"
            #Get Webpart Manager for Form
            $wpm = $formPage.GetLimitedWebPartManager([Microsoft.SharePoint.Client.WebParts.PersonalizationScope]::Shared)

            #Import Webpart on page
            $wp = $wpm.ImportWebPart($webpartXml)

            #Add webpart to Form
            $wpm.AddWebPart($wp.WebPart, "Main", 1) | Out-Null

            #Execute changes
            $List.Context.ExecuteQuery()
        }
        catch
        {
            Write-Error "Error creating form $FormType at $FormUrl. Error: $($_.Exception)"
        }
    }
    end { }
}

#############################################

$csvRows = ConvertFrom-Csv (Get-Content $CSVPath)

if ($null -eq $csvRows) {
    Write-Error "Unable to find CSV at path $CSVPath"
    break
}

foreach ($row in $csvRows)
{
    Write-Output "[$($row.siteUrl)] [$($row.listTitle)]"

    if($UseWebLogin) {
        Connect-PnPOnline -Url $row.siteUrl -UseWebLogin
    }
    else {
        Connect-PnPOnline -Url $row.siteUrl
    }
    $list = Get-PnPList $row.listTitle
    $listUrl = $list.RootFolder.ServerRelativeUrl

    # Handle Document Library Types
    if ($list.BaseType -eq [Microsoft.SharePoint.Client.BaseType]::DocumentLibrary) {
        Write-Host " > Processing Library: $listUrl"
        Create-DefaultListForm -List $list -FormUrl "$listUrl/Forms/Upload.aspx"   -FormType New
        Create-DefaultListForm -List $list -FormUrl "$listUrl/Forms/DispForm.aspx" -FormType Display
        Create-DefaultListForm -List $list -FormUrl "$listUrl/Forms/EditForm.aspx" -FormType Edit
    }

    # Handle Generic List Types
    else {
        Write-Host " > Processing List: $listUrl"
        Create-DefaultListForm -List $list -FormUrl "$listUrl/NewForm.aspx"  -FormType New
        Create-DefaultListForm -List $list -FormUrl "$listUrl/DispForm.aspx" -FormType Display
        Create-DefaultListForm -List $list -FormUrl "$listUrl/EditForm.aspx" -FormType Edit
    }
}