[ntcore] Add hidden subscribe option (#6376)

This allows creating subscribers that aren't communicated with the network.

ntcore/src/main/native/cpp/LocalStorage.cpp

@@ -611,7 +611,7 @@ LocalStorage::SubscriberData* LocalStorage::Impl::AddLocalSubscriber(
         "published as '{}')",
         topic->name, config.typeStr, topic->typeStr);
   }
-  if (m_network) {
+  if (m_network && !subscriber->config.hidden) {
     DEBUG4("-> NetworkSubscribe({})", topic->name);
     m_network->Subscribe(subscriber->handle, {{topic->name}}, config);
   }
@@ -640,7 +640,7 @@ LocalStorage::Impl::RemoveLocalSubscriber(NT_Subscriber subHandle) {
         listener.getSecond()->subscriber = nullptr;
       }
     }
-    if (m_network) {
+    if (m_network && !subscriber->config.hidden) {
       m_network->Unsubscribe(subscriber->handle);
     }
   }
@@ -676,7 +676,7 @@ LocalStorage::MultiSubscriberData* LocalStorage::Impl::AddMultiSubscriber(
       }
     }
   }
-  if (m_network) {
+  if (m_network && !subscriber->options.hidden) {
     DEBUG4("-> NetworkSubscribe");
     m_network->Subscribe(subscriber->handle, subscriber->prefixes,
                          subscriber->options);
@@ -696,7 +696,7 @@ LocalStorage::Impl::RemoveMultiSubscriber(NT_MultiSubscriber subHandle) {
         listener.getSecond()->multiSubscriber = nullptr;
       }
     }
-    if (m_network) {
+    if (m_network && !subscriber->options.hidden) {
       m_network->Unsubscribe(subscriber->handle);
     }
   }
@@ -1128,12 +1128,16 @@ void LocalStorage::Impl::StartNetwork(net::NetworkInterface* network) {
     }
   }
   for (auto&& subscriber : m_subscribers) {
-    network->Subscribe(subscriber->handle, {{subscriber->topic->name}},
-                       subscriber->config);
+    if (!subscriber->config.hidden) {
+      network->Subscribe(subscriber->handle, {{subscriber->topic->name}},
+                         subscriber->config);
+    }
   }
   for (auto&& subscriber : m_multiSubscribers) {
-    network->Subscribe(subscriber->handle, subscriber->prefixes,
-                       subscriber->options);
+    if (!subscriber->options.hidden) {
+      network->Subscribe(subscriber->handle, subscriber->prefixes,
+                         subscriber->options);
+    }
   }
 }
 

ntcore/src/main/native/cpp/jni/NetworkTablesJNI.cpp

@@ -139,6 +139,7 @@ static nt::PubSubOptions FromJavaPubSubOptions(JNIEnv* env, jobject joptions) {
   FIELD(disableRemote, "Z");
   FIELD(disableLocal, "Z");
   FIELD(excludeSelf, "Z");
+  FIELD(hidden, "Z");
 
 #undef FIELD
 
@@ -154,7 +155,8 @@ static nt::PubSubOptions FromJavaPubSubOptions(JNIEnv* env, jobject joptions) {
           FIELD(bool, Boolean, prefixMatch),
           FIELD(bool, Boolean, disableRemote),
           FIELD(bool, Boolean, disableLocal),
-          FIELD(bool, Boolean, excludeSelf)};
+          FIELD(bool, Boolean, excludeSelf),
+          FIELD(bool, Boolean, hidden)};
 
 #undef GET
 #undef FIELD

ntcore/src/main/native/cpp/ntcore_c.cpp

@@ -126,6 +126,7 @@ static PubSubOptions ConvertToCpp(const NT_PubSubOptions* in) {
   out.disableRemote = in->disableRemote;
   out.disableLocal = in->disableLocal;
   out.excludeSelf = in->excludeSelf;
+  out.hidden = in->hidden;
   return out;
 }
 

ntcore/src/main/native/include/ntcore_c.h

@@ -367,6 +367,14 @@ struct NT_PubSubOptions {
    * internal publisher.
    */
   NT_Bool excludeSelf;
+
+  /**
+   * For subscriptions, don't share the existence of the subscription with the
+   * network. Note this means updates will not be received from the network
+   * unless another subscription overlaps with this one, and the subscription
+   * will not appear in metatopics.
+   */
+  NT_Bool hidden;
 };
 
 /**

ntcore/src/main/native/include/ntcore_cpp.h

@@ -374,6 +374,14 @@ struct PubSubOptions {
    * internal publisher.
    */
   bool excludeSelf = false;
+
+  /**
+   * For subscriptions, don't share the existence of the subscription with the
+   * network. Note this means updates will not be received from the network
+   * unless another subscription overlaps with this one, and the subscription
+   * will not appear in metatopics.
+   */
+  bool hidden = false;
 };
 
 /**