Update future swig file preprocessor logic (#934)

* Log additional info

* Update future swig file

* More updates

* Update future.i

* Revert "Log additional info"

This reverts commit 9bded62.

* Update future.i

* Update firestore.i

* Avoid duplicate future void definitions

* Update firestore.i

Author: a-maurice

app/src/swig/app.i

@@ -351,7 +351,9 @@ static firebase::AppOptions* AppOptionsLoadFromJsonConfig(const char* config) {
 
 %SWIG_FUTURE(FutureString, string, internal,
              std::string, FirebaseException)  // Future<std::string>
+#ifndef USE_FIRESTORE_FUTURE_VOID
 %SWIG_FUTURE(FutureVoid, void, internal, void, FirebaseException)
+#endif  // USE_FIRESTORE_FUTURE_VOID
 %SWIG_FUTURE(FutureBool, bool, internal, bool, FirebaseException) // Future<bool>
 
 // Internal

app/src/swig/future.i

@@ -53,12 +53,6 @@ namespace firebase {
 %include "app/src/swig/null_check_this.i"
 %include "app/src/swig/serial_dispose.i"
 
-// This is defined so that it's possible to conditionally generate code that is
-// aware of type void. This allows us to different code for the void type as
-// required by "%extend Future<CTYPE>::result" below.
-%ignore TYPE_void;
-#define TYPE_void 1
-
 // The Future implementation is assembled in a series of three macros,
 // The HEADER, the GET_TASK implementation, and the FOOTER. This componentized
 // approach allows for custom GET_TASK implementations for various SDKs
@@ -110,10 +104,8 @@ namespace firebase {
 // 4) The user's callback executes.
 
 
-// Detect when the CTYPE is void by checking "TYPE_" + CTYPE, which yields:
-// TYPE_void. TYPE_void is only defined for "void" which allows this macro
-// mostly to be used but with some specializations for void.
-#ifdef TYPE_## %mangle(CTYPE)
+// void is a special type since it isn't a real returnable type.
+#if "CTYPE"=="void"
 
 %typemap(cstype, out="System.Threading.Tasks.Task")
   firebase::Future<CTYPE> "CSNAME";
@@ -136,7 +128,7 @@ namespace firebase {
     return CSNAME.GetTask(new CSNAME(future, true));
   }
 
-#endif  //  TYPE_## %mangle(CTYPE)
+#endif  //  "CTYPE"=="void"
 
 // Replace the default Dispose() method to delete the callback data if
 // allocated.
@@ -181,15 +173,15 @@ namespace firebase {
 %define %SWIG_FUTURE_GET_TASK(CSNAME, CSTYPE, CTYPE, EXTYPE)
   // Helper for csout typemap to convert futures into tasks.
   // This would be internal, but we need to share it accross assemblies.
-#ifdef TYPE_## %mangle(CTYPE)
+#if "CTYPE"=="void"
   static public System.Threading.Tasks.Task GetTask(CSNAME fu) {
     System.Threading.Tasks.TaskCompletionSource<int> tcs =
         new System.Threading.Tasks.TaskCompletionSource<int>();
 #else
   static public System.Threading.Tasks.Task<CSTYPE> GetTask(CSNAME fu) {
     System.Threading.Tasks.TaskCompletionSource<CSTYPE> tcs =
         new System.Threading.Tasks.TaskCompletionSource<CSTYPE>();
-#endif  // TYPE_## %mangle(CTYPE)
+#endif  // "CTYPE"=="void"
 
     // Check if an exception has occurred previously and propagate it if it has.
     // This has to be done before accessing the future because the future object
@@ -223,11 +215,11 @@ namespace firebase {
             tcs.SetException(new EXTYPE(error, fu.error_message()));
           } else {
             // Success!
-#ifdef TYPE_## %mangle(CTYPE)
+#if "CTYPE"=="void"
             tcs.SetResult(0);
 #else
             tcs.SetResult(fu.GetResult());
-#endif  // TYPE_## %mangle(CTYPE)
+#endif  // "CTYPE"=="void"
           }
         }
       } catch (System.Exception e) {
@@ -402,10 +394,8 @@ namespace firebase {
     delete reinterpret_cast<CSNAME##CallbackData*>(data);
   }
 
-// Detect when the CTYPE is void by checking "TYPE_" + CTYPE, which yields:
-// TYPE_void. TYPE_void is only defined for "void" which allows the result()
-// method to only be generated for non-void types.
-#ifndef TYPE_## %mangle(CTYPE)
+// Only generate the return logic for non-void types.
+#if "CTYPE"!="void"
 
   // This method copies the value return by Future::result() so that it's
   // possible to marshal the return value to C#.
@@ -417,7 +407,7 @@ namespace firebase {
     return *$self->result();
   }
 
-#endif // !TYPE_void
+#endif // "CTYPE"!="void"
 }
 
 } // namespace firebase

firestore/src/swig/firestore.i

@@ -67,6 +67,11 @@
 // processing meant for `public` methods doesn't get applied.
 %csmethodmodifiers firebase::firestore::Firestore::GetInstance "internal";
 
+// Override the default FutureVoid with a version that throws FirestoreException.
+// Do this before app.i, since that will define FutureVoid, and newer versions
+// of swig only use the first definition of templates.
+#define USE_FIRESTORE_FUTURE_VOID 1
+
 %import "app/src/swig/app.i"
 %import "firestore/src/swig/proxy_helpers.i"
 %include "app/src/swig/init_result.i"