Improves error messages for undefined return value (by Sverre Sundsdal); improves gmock_doctor.

include/gmock/gmock-actions.h

@@ -69,6 +69,8 @@ class ActionAdaptor;
 template <typename T>
 class BuiltInDefaultValue {
  public:
+  // This function returns true iff type T has a built-in default value.
+  static bool Exists() { return false; }
   static T Get() {
     Assert(false, __FILE__, __LINE__,
            "Default action undefined for the function return type.");
@@ -83,6 +85,7 @@ class BuiltInDefaultValue {
 template <typename T>
 class BuiltInDefaultValue<const T> {
  public:
+  static bool Exists() { return BuiltInDefaultValue<T>::Exists(); }
   static T Get() { return BuiltInDefaultValue<T>::Get(); }
 };
 
@@ -91,6 +94,7 @@ class BuiltInDefaultValue<const T> {
 template <typename T>
 class BuiltInDefaultValue<T*> {
  public:
+  static bool Exists() { return true; }
   static T* Get() { return NULL; }
 };
 
@@ -100,6 +104,7 @@ class BuiltInDefaultValue<T*> {
   template <> \
   class BuiltInDefaultValue<type> { \
    public: \
+    static bool Exists() { return true; } \
     static type Get() { return value; } \
   }
 
@@ -191,6 +196,12 @@ class DefaultValue {
   // Returns true iff the user has set the default value for type T.
   static bool IsSet() { return value_ != NULL; }
 
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T>::Exists();
+  }
+
   // Returns the default value for type T if the user has set one;
   // otherwise returns the built-in default value if there is one;
   // otherwise aborts the process.
@@ -220,6 +231,12 @@ class DefaultValue<T&> {
   // Returns true iff the user has set the default value for type T&.
   static bool IsSet() { return address_ != NULL; }
 
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T&>::Exists();
+  }
+
   // Returns the default value for type T& if the user has set one;
   // otherwise returns the built-in default value if there is one;
   // otherwise aborts the process.
@@ -236,6 +253,7 @@ class DefaultValue<T&> {
 template <>
 class DefaultValue<void> {
  public:
+  static bool Exists() { return true; }
   static void Get() {}
 };
 

include/gmock/gmock-spec-builders.h

@@ -1061,15 +1061,21 @@ class FunctionMockerBase : public UntypedFunctionMockerBase {
     return NULL;
   }
 
-  // Performs the default action of this mock function on the given
-  // arguments and returns the result. This method doesn't depend on
-  // the mutable state of this object, and thus can be called
-  // concurrently without locking.
+  // Performs the default action of this mock function on the given arguments
+  // and returns the result. Asserts with a helpful call descrption if there is
+  // no valid return value. This method doesn't depend on the mutable state of
+  // this object, and thus can be called concurrently without locking.
   // L = *
-  Result PerformDefaultAction(const ArgumentTuple& args) const {
+  Result PerformDefaultAction(const ArgumentTuple& args,
+                              const string& call_description) const {
     const DefaultActionSpec<F>* const spec = FindDefaultActionSpec(args);
-    return (spec != NULL) ? spec->GetAction().Perform(args)
-        : DefaultValue<Result>::Get();
+    if (spec != NULL) {
+      return spec->GetAction().Perform(args);
+    }
+    Assert(DefaultValue<Result>::Exists(), "", -1,
+           call_description + "\n    The mock function has no default action "
+           "set, and its return type has no default value set.");
+    return DefaultValue<Result>::Get();
   }
 
   // Registers this function mocker and the mock object owning it;
@@ -1407,7 +1413,7 @@ class InvokeWithHelper {
           Mock::GetReactionOnUninterestingCalls(mocker->MockObject());
 
       // Calculates the function result.
-      Result result = mocker->PerformDefaultAction(args);
+      Result result = mocker->PerformDefaultAction(args, ss.str());
 
       // Prints the function result.
       ss << "\n          Returns: ";
@@ -1429,8 +1435,8 @@ class InvokeWithHelper {
         args, &exp, &action, &is_excessive, &ss, &why);
     ss << "    Function call: " << mocker->Name();
     UniversalPrinter<ArgumentTuple>::Print(args, &ss);
-    Result result =
-        action.IsDoDefault() ? mocker->PerformDefaultAction(args)
+    Result result = action.IsDoDefault() ?
+        mocker->PerformDefaultAction(args, ss.str())
         : action.Perform(args);
     ss << "\n          Returns: ";
     UniversalPrinter<Result>::Print(result, &ss);
@@ -1480,7 +1486,7 @@ class InvokeWithHelper<void, F> {
       const CallReaction reaction =
           Mock::GetReactionOnUninterestingCalls(mocker->MockObject());
 
-      mocker->PerformDefaultAction(args);
+      mocker->PerformDefaultAction(args, ss.str());
       ReportUninterestingCall(reaction, ss.str());
       return;
     }
@@ -1499,7 +1505,7 @@ class InvokeWithHelper<void, F> {
     UniversalPrinter<ArgumentTuple>::Print(args, &ss);
     ss << "\n" << why.str();
     if (action.IsDoDefault()) {
-      mocker->PerformDefaultAction(args);
+      mocker->PerformDefaultAction(args, ss.str());
     } else {
       action.Perform(args);
     }