GetLocalPath returns invalid path when a provider has empty webPath (StrCompLeft matches empty strings) #38

Description

GetLocalPath produces an invalid local path containing the full SharePoint URL when a OneDrive Business provider's ClientPolicy*.ini file lacks a DavUrlNamespace tag (or the file is missing/unreadable), resulting in an empty .webPath for that provider.

This causes Dir() to raise Run-time error '52': Bad file name or number.

Steps to reproduce

1. Have a SharePoint-synced workbook where the corresponding ClientPolicy.ini (or ClientPolicy_*.ini) does not contain a DavUrlNamespace entry
2. Call GetLocalPath(ActiveWorkbook.Path) where the path is a SharePoint URL

Expected result

A valid local path like:

C:\Users\JDoe\OneDrive - Contoso\Shared Documents\Projects\2025\Data

Actual result

C:\Users\JDoe\OneDrive - Contoso\https:\contoso.sharepoint.com\sites\TeamSite\Shared Documents\Projects\2025\Data

Root cause

Two issues:

1. StrCompLeft returns 0 (match) when s2 is empty.

When .webPath is "", the comparison StrCompLeft(odWebPath, "", vbTextCompare) evaluates as:

StrComp(Left$(odWebPath, Len("")), "") → StrComp("", "") → 0  ' Match!

This means a provider with an empty webPath will match any URL input.

2. AddBusinessProviders does not validate tempURL before adding.

The canAdd guard only checks LenB(tempMount) > 0 but not LenB(tempURL) > 0, so providers with empty web paths are added to the cache.

Suggested fix

In StrCompLeft, add an early exit when either string is empty:

Private Function StrCompLeft(ByRef s1 As String _
                           , ByRef s2 As String _
                           , ByVal compareMethod As VbCompareMethod) As Long
    If Len(s1) = 0 Or Len(s2) = 0 Then
        StrCompLeft = -CLng(Len(s1) = 0) + CLng(Len(s2) = 0)
        Exit Function
    End If
    If Len(s1) > Len(s2) Then
        StrCompLeft = StrComp(Left$(s1, Len(s2)), s2, compareMethod)
    Else
        StrCompLeft = StrComp(s1, Left$(s2, Len(s1)), compareMethod)
    End If
End Function

In AddBusinessProviders, change:

If canAdd Then

to:

If canAdd And LenB(tempURL) > 0 Then

Environment

• Windows 11, Excel (Desktop)
• OneDrive for Business syncing SharePoint libraries
• ActiveWorkbook.Path returns a https:// SharePoint URL

Note: This bug report and suggested fix were generated with AI assistance (Claude).