Change pattern to have subtype do json population

src/core/ext/filters/client_channel/client_channel_channelz.cc

@@ -20,6 +20,7 @@
 
 #include "src/core/ext/filters/client_channel/client_channel_channelz.h"
 #include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/transport/connectivity_state.h"
 
 namespace grpc_core {
 namespace channelz {
@@ -36,13 +37,18 @@ static const grpc_arg_pointer_vtable client_channel_channelz_vtable = {
     client_channel_channelz_copy, client_channel_channelz_destroy,
     client_channel_channelz_cmp};
 
-bool ClientChannelNode::GetConnectivityState(grpc_connectivity_state* state) {
-  if (channel()) {
-    *state = grpc_channel_check_connectivity_state(channel(), false);
+void ClientChannelNode::PopulateConnectivityState(grpc_json* json) {
+  grpc_connectivity_state state;
+  if (channel() != nullptr) {
+    state = grpc_channel_check_connectivity_state(channel(), false);
   } else {
-    *state = GRPC_CHANNEL_SHUTDOWN;
+    state = GRPC_CHANNEL_SHUTDOWN;
   }
-  return true;
+  json = grpc_json_create_child(nullptr, json, "state", nullptr,
+                                GRPC_JSON_OBJECT, false);
+  grpc_json_create_child(nullptr, json, "state",
+                         grpc_connectivity_state_name(state), GRPC_JSON_STRING,
+                         false);
 }
 
 grpc_arg ClientChannelNode::CreateArg() {

src/core/ext/filters/client_channel/client_channel_channelz.h

@@ -37,7 +37,7 @@ class ClientChannelNode : public ChannelNode {
 
   // Override this functionality since client_channels have a notion of
   // channel connectivity.
-  bool GetConnectivityState(grpc_connectivity_state* state) override;
+  void PopulateConnectivityState(grpc_json* json) override;
 
   // Helper to create a channel arg to ensure this type of ChannelNode is
   // created.

src/core/lib/channel/channelz.cc

@@ -36,7 +36,6 @@
 #include "src/core/lib/iomgr/error.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/surface/channel.h"
-#include "src/core/lib/transport/connectivity_state.h"
 #include "src/core/lib/transport/error_utils.h"
 
 namespace grpc_core {
@@ -109,9 +108,7 @@ void ChannelNode::RecordCallStarted() {
                            (gpr_atm)ExecCtx::Get()->Now());
 }
 
-bool ChannelNode::GetConnectivityState(grpc_connectivity_state* state) {
-  return false;
-}
+void ChannelNode::PopulateConnectivityState(grpc_json* json) {}
 
 char* ChannelNode::RenderJSON() {
   // We need to track these three json objects to build our object
@@ -132,18 +129,8 @@ char* ChannelNode::RenderJSON() {
                                            GRPC_JSON_OBJECT, false);
   json = data;
   json_iterator = nullptr;
-  // create and fill the connectivity state child.
-  grpc_connectivity_state connectivity_state;
-  if (GetConnectivityState(&connectivity_state)) {
-    json_iterator = grpc_json_create_child(json_iterator, json, "state",
-                                           nullptr, GRPC_JSON_OBJECT, false);
-    json = json_iterator;
-    grpc_json_create_child(nullptr, json, "state",
-                           grpc_connectivity_state_name(connectivity_state),
-                           GRPC_JSON_STRING, false);
-    // reset the parent to be the data object.
-    json = data;
-  }
+
+  PopulateConnectivityState(json);
   json_iterator = grpc_json_create_child(
       json_iterator, json, "target", target_.get(), GRPC_JSON_STRING, false);
   // fill in the channel trace if applicable

src/core/lib/channel/channelz.h

@@ -57,12 +57,10 @@ class ChannelNode : public RefCounted<ChannelNode> {
 
   char* RenderJSON();
 
-  // helper for getting connectivity state. It is virtual because it allows
-  // the client_channel code to live in ext/ instead of lib/
-  //
-  // returns true if the channel has a notion of a connectivity state. In that
-  // case it also sets state to the correct connectivity state.
-  virtual bool GetConnectivityState(grpc_connectivity_state* state);
+  // helper for getting and populating connectivity state. It is virtual
+  // because it allows the client_channel specific code to live in ext/
+  // instead of lib/
+  virtual void PopulateConnectivityState(grpc_json* json);
 
   ChannelTrace* trace() { return trace_.get(); }