fix

private/buf/buflsp/file.go

@@ -234,8 +234,11 @@ func (f *file) RefreshAST(ctx context.Context) bool {
 func (f *file) PublishDiagnostics(ctx context.Context) {
 	defer slogext.DebugProfile(f.lsp.logger, slog.String("uri", string(f.uri)))()
 
+	// NOTE: We need to avoid sending a JSON null here, so we replace it with
+	// a non-nil empty slice when the diagnostics slice is nil.
+	diagnostics := f.diagnostics
 	if f.diagnostics == nil {
-		return
+		diagnostics = []protocol.Diagnostic{}
 	}
 
 	// Publish the diagnostics. This error is automatically logged by the LSP framework.
@@ -244,7 +247,7 @@ func (f *file) PublishDiagnostics(ctx context.Context) {
 		// NOTE: For some reason, Version is int32 in the document struct, but uint32 here.
 		// This seems like a bug in the LSP protocol package.
 		Version:     uint32(f.version),
-		Diagnostics: f.diagnostics,
+		Diagnostics: diagnostics,
 	})
 }