log instead of assert for duplicate object identifiers

Summary: The `IGFailAssert` for duplicate object identifiers causes unit tests to fail in CI / IGListKit because assertions aren't silenced. Changing this to a log for now.

Reviewed By: rnystrom

Differential Revision: D8773452

fbshipit-source-id: 369415fda4ba3eef8fe8684dc792b0a9905a4759

CHANGELOG.md

@@ -21,6 +21,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Ensuring view models with duplicate diff identifiers are removed when view models are first requested by `IGListBindingSectionController` [Adam Stern](https://github.com/adamastern) (tbd)
 
+- Log instead of assert for duplicate diff identifiers to make code testable. [Adam Stern](https://github.com/adamastern) (tbd)
+
 3.4.0
 -----
 

Source/Common/Internal/IGListArrayUtilsInternal.h

@@ -25,7 +25,7 @@ static NSArray *objectsWithDuplicateIdentifiersRemoved(NSArray<id<IGListDiffable
             [identifierMap setObject:object forKey:diffIdentifier];
             [uniqueObjects addObject:object];
         } else {
-            IGFailAssert(@"Duplicate identifier %@ for object %@ with object %@", diffIdentifier, object, previousObject);
+            IGLKLog(@"Duplicate identifier %@ for object %@ with object %@", diffIdentifier, object, previousObject);
         }
     }
     return uniqueObjects;