Improve error message for typeerrors (#785)

* Add a test

* Catch TypeErrorException

* Make exception asserts check error type

* Remove commented-out testcase and check for error type

* Test for Error, not TypeError

src/js_realm_object.hpp

@@ -107,6 +107,9 @@ bool RealmObjectClass<T>::set_property(ContextType ctx, ObjectType object, const
     try {
         realm_object->set_property_value(ctx, property, value, true);
     }
+    catch (TypeErrorException &ex) {
+        throw TypeErrorException(realm_object->get_object_schema().name + "." + std::string(property), ex.type());
+    }
     catch (InvalidPropertyException &ex) {
         return false;
     }

src/js_types.hpp

@@ -71,6 +71,22 @@ struct Context {
     static AbstractExecutionContextID get_execution_context_id(ContextType);
 };
 
+class TypeErrorException : public std::invalid_argument {
+public:
+    std::string const& prefix() const { return m_prefix; }
+    std::string const& type() const { return m_type; }
+
+    TypeErrorException(std::string prefix, std::string type) : 
+        std::invalid_argument(prefix + " must be of type: " + type),
+        m_prefix(std::move(prefix)),
+        m_type(std::move(type)) 
+        {}
+
+private:
+    std::string m_prefix;
+    std::string m_type;
+};
+
 template<typename T>
 struct Value {
     using ContextType = typename T::Context;
@@ -111,7 +127,7 @@ struct Value {
     static return_t validated_to_##type(ContextType ctx, const ValueType &value, const char *name = nullptr) { \
         if (!is_##type(ctx, value)) { \
             std::string prefix = name ? std::string("'") + name + "'" : "JS value"; \
-            throw std::invalid_argument(prefix + " must be of type: " #type); \
+            throw TypeErrorException(prefix, #type); \
         } \
         return to_##type(ctx, value); \
     }

tests/js/asserts.js

@@ -107,6 +107,9 @@ module.exports = {
         }
         catch (e) {
             caught = true;
+            if (e.name !== expectedException.name) {
+                throw new TestFailureError('Expected a ' + expectedException.name + ' exception but caught a ' + e.name + ' instead. Message was: ' + e.message);
+            }
             if (e.message != expectedException.message) {
                 throw new TestFailureError('Expected exception "' + expectedException + '" not thrown - instead caught: "' + e + '"');
             }

tests/js/realm-tests.js

@@ -866,4 +866,15 @@ module.exports = {
         realm = new Realm({path: 'dates-v5.realm', schema: [schemas.DateObject]});
         TestCase.assertEqual(realm.objects('Date')[0].currentDate.getTime(), 1);
     },
+
+    testErrorMessageFromInvalidWrite: function() {
+        var realm = new Realm({schema: [schemas.PersonObject]});
+        
+        TestCase.assertThrowsException(function() {
+            realm.write(function () {
+                var p1 = realm.create('PersonObject', { name: 'Ari', age: 10 });
+                p1.age = "Ten";
+            });
+        }, new Error("PersonObject.age must be of type: number"));
+    }
 };