--- a/mercurial/mdiff.py	Sat Sep 28 19:12:18 2024 -0400
+++ b/mercurial/mdiff.py	Sun Sep 29 02:03:20 2024 -0400
@@ -212,7 +212,11 @@
 
 
 def chooseblocksfunc(opts=None):
-    if opts is None or not opts.xdiff or not hasattr(bdiff, 'xdiffblocks'):
+    if (
+        opts is None
+        or not opts.xdiff
+        or not getattr(bdiff, 'xdiffblocks', None)
+    ):
         return bdiff.blocks
     else:
         return bdiff.xdiffblocks