handle diffProperties as well

Author: hannojg

packages/react-native-renderer/src/ReactNativeAttributePayloadFabric.js

@@ -287,14 +287,23 @@ function diffProperties(
     prevProp = prevProps[propKey];
     nextProp = nextProps[propKey];
 
-    // functions are converted to booleans as markers that the associated
-    // events should be sent from native.
     if (typeof nextProp === 'function') {
-      nextProp = (true: any);
-      // If nextProp is not a function, then don't bother changing prevProp
-      // since nextProp will win and go into the updatePayload regardless.
-      if (typeof prevProp === 'function') {
-        prevProp = (true: any);
+      if (typeof attributeConfig === 'object') {
+        // When the config for a function prop has a custom process method
+        // we don't assume its a regular event handler, but use the process method:
+        nextProp = attributeConfig.process(nextProp);
+        if (typeof prevProp === 'function') {
+          prevProp = attributeConfig.process(prevProp);
+        }
+      } else {
+        // functions are converted to booleans as markers that the associated
+        // events should be sent from native.
+        nextProp = (true: any);
+        // If nextProp is not a function, then don't bother changing prevProp
+        // since nextProp will win and go into the updatePayload regardless.
+        if (typeof prevProp === 'function') {
+          prevProp = (true: any);
+        }
       }
     }
 

packages/react-native-renderer/src/__tests__/ReactNativeAttributePayloadFabric-test.internal.js

@@ -461,4 +461,21 @@ describe('ReactNativeAttributePayloadFabric.diff', () => {
       ),
     ).toEqual(null);
   });
+
+  it('should use the process function config when prop is a function', () => {
+    const process = jest.fn(a => a);
+    const nextFunction = function () {}
+    expect(
+      diff(
+        {
+          a: function () {},
+        },
+        {
+          a: nextFunction,
+        },
+        {a: {process}},
+      ),
+    ).toEqual({a: nextFunction});
+    expect(process).toBeCalled()
+  })
 });