DynamicObject: Update signature of clone to return unique_ptr

BREAKING-CHANGES.txt

@@ -1,6 +1,33 @@
 JUCE breaking changes
 =====================
 
+develop
+=======
+
+Change
+------
+DynamicObject::clone now returns unique_ptr<DynamicObject> instead of
+ReferenceCountedObjectPtr<DynamicObject>.
+
+Possible Issues
+---------------
+Overrides of this function using the old signature will fail to compile.
+The result of this function may need to be manually converted to a
+ReferenceCountedObjectPtr.
+
+Workaround
+----------
+Update overrides to use the new signature.
+If necessary, manually construct a ReferenceCountedObjectPtr at call sites.
+
+Rationale
+---------
+It's easy to safely upgrade a unique_ptr to a shared/refcounted pointer.
+However, it's not so easy to convert safely in the opposite direction.
+Generally, returning unique_ptrs rather than refcounted pointers leads to more
+flexible APIs.
+
+
 Version 7.0.7
 =============
 

modules/juce_core/containers/juce_DynamicObject.cpp

@@ -87,11 +87,11 @@ void DynamicObject::cloneAllProperties()
             *v = v->clone();
 }
 
-DynamicObject::Ptr DynamicObject::clone()
+std::unique_ptr<DynamicObject> DynamicObject::clone() const
 {
-    Ptr d (new DynamicObject (*this));
-    d->cloneAllProperties();
-    return d;
+    auto result = std::make_unique<DynamicObject> (*this);
+    result->cloneAllProperties();
+    return result;
 }
 
 void DynamicObject::writeAsJSON (OutputStream& out, const int indentLevel, const bool allOnOneLine, int maximumDecimalPlaces)

modules/juce_core/containers/juce_DynamicObject.h

@@ -107,7 +107,7 @@ public:
         with a (deep) copy of all of its properties. Subclasses can override this to
         implement their own custom copy routines.
     */
-    virtual Ptr clone();
+    virtual std::unique_ptr<DynamicObject> clone() const;
 
     //==============================================================================
     /** Writes this object to a text stream in JSON format.

modules/juce_core/containers/juce_Variant.cpp

@@ -314,7 +314,7 @@ struct var::VariantType
     static var objectClone (const var& original)
     {
         if (auto* d = original.getDynamicObject())
-            return d->clone().get();
+            return d->clone().release();
 
         jassertfalse; // can only clone DynamicObjects!
         return {};

modules/juce_core/javascript/juce_Javascript.cpp

@@ -833,7 +833,7 @@ struct JavascriptEngine::RootObject   : public DynamicObject
             tb.parseFunctionParamsAndBody (*this);
         }
 
-        DynamicObject::Ptr clone() override    { return *new FunctionObject (*this); }
+        std::unique_ptr<DynamicObject> clone() const override    { return std::make_unique<FunctionObject> (*this); }
 
         void writeAsJSON (OutputStream& out, int /*indentLevel*/, bool /*allOnOneLine*/, int /*maximumDecimalPlaces*/) override
         {