[ConfigImpact] Compare unchecked callees if lengths are the same

Summary: One source of non-deterministic diff result is when there are multiple overloaded methods the cardinals of unchecked callees of which are the same.  This diff tries to select one of them in a more deterministic manner.

Reviewed By: ezgicicek, ngorogiannis

Differential Revision: D27430757

fbshipit-source-id: 38ba5d8dc

infer/src/integration/Differential.ml

@@ -406,7 +406,8 @@ module ConfigImpactItem = struct
   type change_type = Added | Removed
 
   let compare_by_unchecked_callees_length {unchecked_callees= u1} {unchecked_callees= u2} =
-    Int.compare (UncheckedCallees.cardinal u1) (UncheckedCallees.cardinal u2)
+    let c = Int.compare (UncheckedCallees.cardinal u1) (UncheckedCallees.cardinal u2) in
+    if c <> 0 then c else UncheckedCallees.compare u1 u2
 
 
   let pp_change_type f x =