lib/regexp-examples/backreferences.rb in regexp-examples-0.3.2 vs lib/regexp-examples/backreferences.rb in regexp-examples-0.4.0

@@ -1,20 +1,26 @@
 module RegexpExamples
   class BackReferenceReplacer
     def substitute_backreferences(full_examples)
       full_examples.map do |full_example|
-        while full_example.match(/__(\w+?)__/)
-          full_example.sub!(/__(\w+?)__/, find_backref_for(full_example, $1))
+        begin
+          while full_example.match(/__(\w+?)__/)
+            full_example.sub!(/__(\w+?)__/, find_backref_for(full_example, $1))
+          end
+          full_example
+        rescue RegexpExamples::BackrefNotFound
+          # For instance, one "full example" from /(a|(b)) \2/: "a __2__"
+          # should be rejected because the backref (\2) does not exist
+          nil
         end
-        full_example
-      end
+      end.compact
     end
 
     private
     def find_backref_for(full_example, group_id)
       full_example.all_subgroups.detect do |subgroup|
         subgroup.group_id == group_id
-      end
+      end || raise(RegexpExamples::BackrefNotFound)
     end
 
   end
 
 end