Address review: keep interface-compatible signature; cover explicit false capability

- Revert GetRegistrationOptions parameter to the non-nullable RenameCapability
  declared by IPrepareRenameHandler/IRenameHandler, and rely on the
  null-conditional check (capability?.PrepareSupport == true) for the runtime
  case where the framework passes a null capability. This matches the OmniSharp
  interface signature exactly, avoiding any nullable-annotation mismatch
  (e.g. CS8765) while remaining null-safe during initialize.
- Add explicit { false, false } theory cases for both handler kinds so the
  three distinct PrepareSupport inputs (omitted/null, true, false) are all
  covered and a regression that treats false as enabled would be caught.

Verified: src and test projects build with 0 warnings under #nullable enable;
all 6 GetRegistrationOptionsReflectsPrepareSupport cases pass on net462 and net8.0.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mgreenegit

src/PowerShellEditorServices/Services/TextDocument/Handlers/RenameHandler.cs

@@ -20,7 +20,7 @@ internal class PrepareRenameHandler
     RenameService renameService
 ) : IPrepareRenameHandler
 {
-    public RenameRegistrationOptions GetRegistrationOptions(RenameCapability? capability, ClientCapabilities clientCapabilities) => capability?.PrepareSupport == true ? new() { PrepareProvider = true } : new();
+    public RenameRegistrationOptions GetRegistrationOptions(RenameCapability capability, ClientCapabilities clientCapabilities) => capability?.PrepareSupport == true ? new() { PrepareProvider = true } : new();
 
     public async Task<RangeOrPlaceholderRange?> Handle(PrepareRenameParams request, CancellationToken cancellationToken)
         => await renameService.PrepareRenameSymbol(request, cancellationToken).ConfigureAwait(false);
@@ -34,9 +34,9 @@ RenameService renameService
 ) : IRenameHandler
 {
     // RenameOptions may only be specified if the client states that it supports prepareSupport in its initial initialize request.
-    // Passes a null capability when the client omits textDocument.rename from its advertised capabilities (e.g. a completion-only client).
-    // Use the null-conditional operator so we don't throw NullReferenceException during initialize.
-    public RenameRegistrationOptions GetRegistrationOptions(RenameCapability? capability, ClientCapabilities clientCapabilities) => capability?.PrepareSupport == true ? new() { PrepareProvider = true } : new();
+    // The framework passes a null capability when the client omits textDocument.rename from its advertised capabilities (e.g. a completion-only client).
+    // The parameter keeps the interface's non-nullable signature; the null-conditional operator avoids a NullReferenceException during initialize.
+    public RenameRegistrationOptions GetRegistrationOptions(RenameCapability capability, ClientCapabilities clientCapabilities) => capability?.PrepareSupport == true ? new() { PrepareProvider = true } : new();
 
     public async Task<WorkspaceEdit?> Handle(RenameParams request, CancellationToken cancellationToken)
         => await renameService.RenameSymbol(request, cancellationToken).ConfigureAwait(false);

test/PowerShellEditorServices.Test/Refactoring/RenameHandlerTests.cs

@@ -134,12 +134,15 @@ public enum RegistrationHandlerKind
         PrepareRename
     }
 
-    // A null prepareSupport represents the client omitting the capability entirely (framework hands us null).
+    // prepareSupport has three distinct inputs: null = client omitted the capability entirely (framework hands us null),
+    // true = client supports prepareRename, false = client explicitly does not. Only true should enable PrepareProvider.
     public static TheoryData<RegistrationHandlerKind, bool?, bool> RegistrationOptionsTestCases() => new()
     {
         { RegistrationHandlerKind.Rename, null, false },
+        { RegistrationHandlerKind.Rename, false, false },
         { RegistrationHandlerKind.Rename, true, true },
         { RegistrationHandlerKind.PrepareRename, null, false },
+        { RegistrationHandlerKind.PrepareRename, false, false },
         { RegistrationHandlerKind.PrepareRename, true, true }
     };