Add tfprotov{5,6}.NoListResults for convenience (#529)

Author: bbasata

tfprotov5/list_resource.go

@@ -53,6 +53,9 @@ type ListResourceServerStream struct {
 	Results iter.Seq[ListResourceResult]
 }
 
+// NoListResults is a convenient value to return when there are no list results.
+var NoListResults = func(func(ListResourceResult) bool) {}
+
 type ListResourceResult struct { // TODO: propose rename in protocol: ListResource_Event -> ListResource_Result
 	// DisplayName is the display name of the resource. This is a ...
 	DisplayName string

tfprotov5/tf5server/server.go

@@ -1210,8 +1210,7 @@ func (s *server) ValidateListResourceConfig(ctx context.Context, protoReq *tfplu
 
 	ctx = tf5serverlogging.DownstreamRequest(ctx)
 
-	// TODO: Remove this check and error in preference of
-	// s.downstream.ValidateListResourceConfig below once ProviderServer interface
+	// TODO: Remove this check and error once ProviderServer interface
 	// implements this RPC method.
 	// nolint:staticcheck
 	listResourceServer, ok := s.downstream.(tfprotov5.ProviderServerWithListResource)

tfprotov6/list_resource.go

@@ -53,6 +53,9 @@ type ListResourceServerStream struct {
 	Results iter.Seq[ListResourceResult]
 }
 
+// NoListResults is a convenient value to return when there are no list results.
+var NoListResults = func(func(ListResourceResult) bool) {}
+
 type ListResourceResult struct { // TODO: propose rename in protocol: ListResource_Event -> ListResource_Result
 	// DisplayName is the display name of the resource. This is a ...
 	DisplayName string

tfprotov6/tf6server/server.go

@@ -1264,8 +1264,7 @@ func (s *server) ListResource(protoReq *tfplugin6.ListResource_Request, protoStr
 
 	ctx = tf6serverlogging.DownstreamRequest(ctx)
 
-	// TODO: Remove this check and error in preference of
-	// s.downstream.ValidateListResourceConfig below once ProviderServer interface
+	// TODO: Remove this check and error once ProviderServer interface
 	// implements this RPC method.
 	// nolint:staticcheck
 	downstream, ok := s.downstream.(tfprotov6.ProviderServerWithListResource)