Use a fresh NullDataloader instance for run_isolated to support frozen instances

Author: rmosolgo

lib/graphql/dataloader.rb

@@ -163,6 +163,8 @@ def run_isolated
       prev_pending_keys = {}
       prev_lazies_at_depth = @lazies_at_depth
       @lazies_at_depth = @lazies_at_depth.dup.clear
+      # Clear pending loads but keep already-cached records
+      # in case they are useful to the given block.
       @source_cache.each do |source_class, batched_sources|
         batched_sources.each do |batch_args, batched_source_instance|
           if batched_source_instance.pending?

lib/graphql/dataloader/null_dataloader.rb

@@ -37,14 +37,17 @@ def run(trace_query_lazy: nil)
       end
 
       def run_isolated
-        prev_lazies_at_depth = @lazies_at_depth
-        @lazies_at_depth = @lazies_at_depth.dup.clear
-        yield
-      ensure
-        @lazies_at_depth = prev_lazies_at_depth
+        new_dl = self.class.new
+        res = nil
+        new_dl.append_job {
+          res = yield
+        }
+        new_dl.run
+        res
       end
 
       def clear_cache; end
+
       def yield(_source)
         raise GraphQL::Error, "GraphQL::Dataloader is not running -- add `use GraphQL::Dataloader` to your schema to use Dataloader sources."
       end