Merge isObject branches (#21226)

We assume that isArray and getIteratorFn are only called on objects. So we shouldn't have to check that again and again, and then check a flag. We can just stay in this branch. There is a slight semantic breakage here because you could have an iterator on a function, such as if it's a generator function. But that's not supported and that currently only works at the root. The inner slots don't support this. So this just makes it consistent.
facebook · Apr 9, 2021 · 3971371 · 3971371
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commit 3971371
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diff --git a/packages/react-reconciler/src/ReactChildFiber.new.js b/packages/react-reconciler/src/ReactChildFiber.new.js
@@ -1231,9 +1231,7 @@ function ChildReconciler(shouldTrackSideEffects) {
     }
 
     // Handle object types
-    const isObject = typeof newChild === 'object' && newChild !== null;
-
-    if (isObject) {
+    if (typeof newChild === 'object' && newChild !== null) {
       switch (newChild.$$typeof) {
         case REACT_ELEMENT_TYPE:
           return placeSingleChild(
@@ -1266,6 +1264,26 @@ function ChildReconciler(shouldTrackSideEffects) {
             );
           }
       }
+
+      if (isArray(newChild)) {
+        return reconcileChildrenArray(
+          returnFiber,
+          currentFirstChild,
+          newChild,
+          lanes,
+        );
+      }
+
+      if (getIteratorFn(newChild)) {
+        return reconcileChildrenIterator(
+          returnFiber,
+          currentFirstChild,
+          newChild,
+          lanes,
+        );
+      }
+
+      throwOnInvalidObjectType(returnFiber, newChild);
     }
 
     if (typeof newChild === 'string' || typeof newChild === 'number') {
@@ -1279,28 +1297,6 @@ function ChildReconciler(shouldTrackSideEffects) {
       );
     }
 
-    if (isArray(newChild)) {
-      return reconcileChildrenArray(
-        returnFiber,
-        currentFirstChild,
-        newChild,
-        lanes,
-      );
-    }
-
-    if (getIteratorFn(newChild)) {
-      return reconcileChildrenIterator(
-        returnFiber,
-        currentFirstChild,
-        newChild,
-        lanes,
-      );
-    }
-
-    if (isObject) {
-      throwOnInvalidObjectType(returnFiber, newChild);
-    }
-
     if (__DEV__) {
       if (typeof newChild === 'function') {
         warnOnFunctionType(returnFiber);

diff --git a/packages/react-reconciler/src/ReactChildFiber.old.js b/packages/react-reconciler/src/ReactChildFiber.old.js
@@ -1231,9 +1231,7 @@ function ChildReconciler(shouldTrackSideEffects) {
     }
 
     // Handle object types
-    const isObject = typeof newChild === 'object' && newChild !== null;
-
-    if (isObject) {
+    if (typeof newChild === 'object' && newChild !== null) {
       switch (newChild.$$typeof) {
         case REACT_ELEMENT_TYPE:
           return placeSingleChild(
@@ -1266,6 +1264,26 @@ function ChildReconciler(shouldTrackSideEffects) {
             );
           }
       }
+
+      if (isArray(newChild)) {
+        return reconcileChildrenArray(
+          returnFiber,
+          currentFirstChild,
+          newChild,
+          lanes,
+        );
+      }
+
+      if (getIteratorFn(newChild)) {
+        return reconcileChildrenIterator(
+          returnFiber,
+          currentFirstChild,
+          newChild,
+          lanes,
+        );
+      }
+
+      throwOnInvalidObjectType(returnFiber, newChild);
     }
 
     if (typeof newChild === 'string' || typeof newChild === 'number') {
@@ -1279,28 +1297,6 @@ function ChildReconciler(shouldTrackSideEffects) {
       );
     }
 
-    if (isArray(newChild)) {
-      return reconcileChildrenArray(
-        returnFiber,
-        currentFirstChild,
-        newChild,
-        lanes,
-      );
-    }
-
-    if (getIteratorFn(newChild)) {
-      return reconcileChildrenIterator(
-        returnFiber,
-        currentFirstChild,
-        newChild,
-        lanes,
-      );
-    }
-
-    if (isObject) {
-      throwOnInvalidObjectType(returnFiber, newChild);
-    }
-
     if (__DEV__) {
       if (typeof newChild === 'function') {
         warnOnFunctionType(returnFiber);