Inconsistent behaviour when using CSOM to create DocumentSets with names containing "#" or "%"

[ltdu]

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

SharePoint CSOM

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Microsoft.SharePointOnline.CSOM: 16.1.24322.12000

Describe the bug / error

Special characters # and % are supported in paths and file/folder names for some time:

Supporting % and # in files and folders with the ResourcePath API

While this page does not mention Document Sets, you can use standard SharePoint UI to create new document set containing both of these characters:

However, if you try to create new document set using CSOM, results are inconsistent:

• If # is used, error message "File Not Found." is returned
• if % is used which is followed by some numeric value, it will be URL-decoded into another character
• if % is used and it cannot be URL-decoded, document set is created with correct name

Steps to reproduce

1. Enable Document Sets feature
2. Create standard document library
3. Add Document Set content type to it
4. Use CSOM code to create new document sets:

using var clientContext = new ClientContext("https://___.sharepoint.com/sites/demo-docset-issue");
clientContext.ExecutingWebRequest += await AttachAuthorization();

var listUrl = "/sites/demo-docset-issue/docs";
var ctypeId = "0x0120D52000639392D323B55A4FAC637C3B25FA070D";

var web = clientContext.Web;
var list = web.GetList(listUrl);
var ctype = list.ContentTypes.GetById(ctypeId);
var folder = list.RootFolder;

clientContext.Load(folder);
clientContext.Load(ctype);
await clientContext.ExecuteQueryAsync();

// Following throws exception with message "File Not Found."

try
{
    var docSetName1 = "Test # 123";
    var docSetUrl1 = DocumentSet.Create(clientContext, folder, docSetName1, ctype.Id);
    await clientContext.ExecuteQueryAsync();
    Console.WriteLine(docSetUrl1.Value);
}
catch (Exception ex1)
{
    Console.WriteLine(ex1.Message);
}

// This one create document set with different name and returns
// https://___.sharepoint.com/sites/demo-docset-issue/docs/Test 3

try
{
    var docSetName2 = "Test %123";
    var docSetUrl2 = DocumentSet.Create(clientContext, folder, docSetName2, ctype.Id);
    await clientContext.ExecuteQueryAsync();
    Console.WriteLine(docSetUrl2.Value);
}
catch (Exception ex2)
{
    Console.WriteLine(ex2.Message);
}

// Document set with correct name is created:
// https://___.sharepoint.com/sites/demo-docset-issue/docs/Test % 123

try
{
    var docSetName3 = "Test % 123";
    var docSetUrl3 = DocumentSet.Create(clientContext, folder, docSetName3, ctype.Id);
    await clientContext.ExecuteQueryAsync();
    Console.WriteLine(docSetUrl3.Value);
}
catch (Exception ex3)
{
    Console.WriteLine(ex3.Message);
}

Expected behavior

It is expected for CSOM to work correctly and create document sets with provided names.

Additional note 1: it seems JSOM partially works with # - error message is not return, however name is changed so that only part of provided value remains (Test 1#23 becomes Test 1).

Additional note 2: while standard UI is able to create document set with #, most likely it creates folder without it and renames afterwards; and if that folder already exists - it throws an error:

[ghost]

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