lib/regexp-examples/backreferences.rb in regexp-examples-1.1.3 vs lib/regexp-examples/backreferences.rb in regexp-examples-1.1.4

@@ -1,37 +1,53 @@
 module RegexpExamples
+  # A helper class to fill-in backrefences AFTER the example(s) have been generated.
+  # In a nutshell, this works by doing the following:
+  # * Given a regex that contains a capute group and backreference, e.g. `/(a|b) \1/`
+  # * After generating examples, the backreference is tored as a placeholder:
+  #   `["a __1__", "b __1__"]`
+  # * This class is used to fill in each placeholder accordingly:
+  #   `["a a", "b b"]`
+  # * Also, beware of octal groups and cases where the backref invalidates the example!!
   class BackReferenceReplacer
-    BackrefNotFound = Class.new(StandardError)
+    # Named capture groups can only contain alphanumeric chars, and hyphens
+    PLACEHOLDER_REGEX = Regexp.new(
+      RegexpExamples::BackReferenceGroup::PLACEHOLDER_FORMAT % '([a-zA-Z0-9-]+)'
+    )
 
     def substitute_backreferences(full_examples)
       full_examples.map do |full_example|
-        begin
-          while full_example.match(/__(\w+?)__/)
-            full_example.sub!(/__(\w+?)__/, find_backref_for(full_example, Regexp.last_match(1)))
-          end
-          full_example
-        rescue BackrefNotFound
-          # For instance, one "full example" from /(a|(b)) \2/: "a __2__"
-          # should be rejected because the backref (\2) does not exist
-          nil
+        # For instance, one "full example" from /(a|(b)) \2/: "a __2__"
+        # should be rejected because the backref (\2) does not exist
+        catch(:backref_not_found) do
+          substitute_backrefs_one_at_a_time(full_example)
         end
       end.compact
     end
 
     private
 
+    def substitute_backrefs_one_at_a_time(full_example)
+      while full_example.match(PLACEHOLDER_REGEX)
+        full_example.sub!(
+          PLACEHOLDER_REGEX,
+          find_backref_for(full_example, Regexp.last_match(1))
+        )
+      end
+      full_example
+    end
+
     def find_backref_for(full_example, group_id)
       full_example.all_subgroups.detect do |subgroup|
         subgroup.group_id == group_id
       end || octal_char_for(group_id)
     end
 
     def octal_char_for(octal_chars)
-      # For octal characters in the range \10 - \177
-      if octal_chars =~ /\A[01]?[0-7]{1,2}\z/ && octal_chars.to_i >= 10
+      # For octal characters in the range \00 - \177
+      if octal_chars =~ /\A[01]?[0-7]{1,2}\z/ && octal_chars.length > 1
         Integer(octal_chars, 8).chr
       else
-        fail(BackrefNotFound)
+        throw :backref_not_found
       end
     end
   end
 end