[LANG] Improve serializer (#1658)

src/lang/attrs.cc

@@ -42,4 +42,6 @@ TVM_STATIC_IR_FUNCTOR(IRPrinter, vtable)
 
 TVM_REGISTER_NODE_TYPE(DictAttrsNode);
 
+TVM_REGISTER_NODE_TYPE(AttrFieldInfoNode);
+
 }  // namespace tvm

src/lang/reflection.cc

@@ -236,6 +236,11 @@ class JSONAttrGetter : public AttrVisitor {
             node_index_->at(kv.second.get()));
       }
     } else {
+      // do not need to recover content of global singleton object
+      // they are registered via the environment
+      auto* f = dmlc::Registry<NodeFactoryReg>::Find(node->type_key());
+      if (f != nullptr && f->fglobal_key != nullptr) return;
+      // recursively index normal object.
       node->VisitAttrs(this);
     }
   }

tests/python/unittest/test_lang_reflection.py

@@ -58,7 +58,8 @@ def test_make_attrs():
 
     dattr = tvm.make.node("DictAttrs", x=1, y=10, name="xyz", padding=(0,0))
     assert dattr.x.value == 1
-
+    datrr = tvm.load_json(tvm.save_json(dattr))
+    assert dattr.name.value == "xyz"
 
 
 def test_make_sum():