Add support for Revit 2027 secure addin manifest location

Background

Starting with Revit 2027, Autodesk is implementing improved file permissions security for addins. The current all-users addin location (%ProgramData%\Autodesk\Revit\Addins\<year>\) will be deprecated and unsupported starting from Revit 2027.

New Addin Paths (Revit 2027+)

Reference: Autodesk Revit 2027 security improvements documentation.

Required Changes

The pyRevit attachment system needs to be updated to handle the new secure location for Revit 2027 and later versions.

Files to Modify

1. dev/pyRevitLabs/pyRevitLabs.TargetApps.Revit/RevitAddons.cs
   • Update GetRevitAddonsFolder() method to return the appropriate path based on Revit version
   • For Revit 2027+, all-users path should be: C:\Program Files\Autodesk\Revit <year>\Addins\<year>\
   • For Revit ≤2026, keep existing behavior: %ProgramData%\Autodesk\Revit\Addins\<year>\
   • User-level installations remain unchanged for all versions

Implementation Details

The GetRevitAddonsFolder() method should:

1. Accept the revitYear parameter (already exists)
2. Check if allUsers == true AND revitYear >= 2027
3. If true, construct path using the Revit installation directory from RevitProduct.InstallLocation property
4. If false (or revitYear < 2027), use the existing logic

Example logic:

public static string GetRevitAddonsFolder(int revitYear, bool allUsers = false) {
    if (allUsers && revitYear >= 2027) {
        // New secure path for Revit 2027+
        // Get the Revit installation path
        var revitProducts = RevitProduct.ListInstalledProducts();
        var targetRevit = revitProducts.FirstOrDefault(r => r.ProductYear == revitYear);
        
        if (targetRevit != null && !string.IsNullOrEmpty(targetRevit.InstallLocation)) {
            return Path.Combine(targetRevit.InstallLocation, "Addins", revitYear.ToString());
        }
        else {
            // Fallback to default expected path
            var defaultPath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles),
                "Autodesk",
                $"Revit {revitYear}",
                "Addins",
                revitYear.ToString()
            );
            return defaultPath;
        }
    }
    else {
        // Existing logic for user-level or Revit ≤2026
        var rootFolder = allUsers ? 
            System.Environment.SpecialFolder.CommonApplicationData : 
            System.Environment.SpecialFolder.ApplicationData;
        return Path.Combine(
            System.Environment.GetFolderPath(rootFolder),
            "Autodesk", 
            "Revit", 
            "Addins", 
            revitYear.ToString()
        );
    }
}

Testing Considerations

• ✅ Verify backward compatibility with Revit 2026 and earlier
• ✅ Verify user-level installations continue to work for all versions
• ✅ Verify all-users installations work with new path for Revit 2027+
• ✅ Ensure the new path is created if it doesn't exist (CommonUtils.EnsureFile() already handles directory creation)
• ✅ Admin privileges are required for writing to C:\Program Files\ (already required for all-users installations)

Additional Considerations

The GetManifest() method should also be updated to search both locations for Revit 2027+ when looking for existing manifests, to handle migration scenarios where old manifests might still exist.

Impact Analysis

• User-level installations: ✅ No impact (path unchanged)
• All-users installations (Revit ≤2026): ✅ No impact (existing path still supported)
• All-users installations (Revit 2027+): ⚠️ Required - must use new secure path
• Existing attachments: Migration may be needed for Revit 2027 upgrades

Documentation Updates

Update documentation to:

• Inform users about the new requirement for Revit 2027+
• Explain that admin installers will write to the new secure location
• Note that old all-users installations will stop working in Revit 2027 unless migrated

Acceptance Criteria

• GetRevitAddonsFolder() returns correct path for all-users installations on Revit 2027+
• Backward compatibility maintained for Revit 2026 and earlier
• User-level installations continue to work unchanged
• Manifest creation succeeds at new location
• Manifest reading succeeds from new location
• Unit tests pass (if applicable)
• Manual testing confirms attachment works in Revit 2027+