Add support for setting non-fatal error block

AsyncDisplayKit/ASDisplayNode.h

@@ -55,6 +55,12 @@ typedef void (^ASDisplayNodeContextModifier)(CGContextRef context);
  */
 typedef ASLayoutSpec * _Nonnull(^ASLayoutSpecBlock)(__kindof ASDisplayNode * _Nonnull node, ASSizeRange constrainedSize);
 
+/**
+ * AsyncDisplayKit non-faltal error block. This block can be used for handling non-fatal errors. Useful for reporting
+ * errors that happens in production.
+ */
+typedef void (^ASDisplayNodeNonFatalErrorBlock)(__kindof NSError * _Nonnull error);
+
 /**
  * Interface state is available on ASDisplayNode and ASViewController, and
  * allows checking whether a node is in an interface situation where it is prudent to trigger certain
@@ -252,6 +258,15 @@ extern NSInteger const ASDefaultDrawingPriority;
  */
 @property (readonly) ASInterfaceState interfaceState;
 
+/**
+ * @abstract Class property that allows to set a block that can be called on non-fatal errors. This
+ * property can be useful for cases when Async Display Kit can recover from an anormal behavior, but
+ * still gives the opportunity to use a reporting mechanism to catch occurrences in production.
+ *
+ * @warning This method is not thread-safe.
+ */
+@property (nonatomic, class, copy) ASDisplayNodeNonFatalErrorBlock nonFatalErrorBlock;
+
 
 /** @name Managing dimensions */
 

AsyncDisplayKit/ASDisplayNode.mm

@@ -63,6 +63,8 @@
   #define TIME_SCOPED(outVar)
 #endif
 
+static ASDisplayNodeNonFatalErrorBlock _nonFatalErrorBlock = nil;
+
 // Forward declare CALayerDelegate protocol as the iOS 10 SDK moves CALayerDelegate from a formal delegate to a protocol.
 // We have to forward declare the protocol as this place otherwise it will not compile compiling with an Base SDK < iOS 10
 @protocol CALayerDelegate;
@@ -2259,6 +2261,20 @@ - (void)subnodeDisplayDidFinish:(ASDisplayNode *)subnode
   return (id)kCFNull;
 }
 
+#pragma mark - Error Handling
+
++ (void)setNonFatalErrorBlock:(ASDisplayNodeNonFatalErrorBlock)nonFatalErrorBlock
+{
+  if (_nonFatalErrorBlock != nonFatalErrorBlock) {
+    _nonFatalErrorBlock = [nonFatalErrorBlock copy];
+  }
+}
+
++ (ASDisplayNodeNonFatalErrorBlock)nonFatalErrorBlock
+{
+  return _nonFatalErrorBlock;
+}
+
 #pragma mark - Converting to and from the Node's Coordinate System
 
 - (CATransform3D)_transformToAncestor:(ASDisplayNode *)ancestor