From 66689fd3526d19393c374c68b8c40470873520c0 Mon Sep 17 00:00:00 2001
From: Thomas Walpole <twalpole@gmail.com>
Date: Thu, 8 Nov 2018 11:04:31 -0800
Subject: [PATCH] Code refactor

---
 lib/capybara/selector/regexp_disassembler.rb | 51 +++++++++++---------
 spec/regexp_dissassembler_spec.rb            | 14 +++++-
 2 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/lib/capybara/selector/regexp_disassembler.rb b/lib/capybara/selector/regexp_disassembler.rb
index 9b24c99b..9ebaead4 100644
--- a/lib/capybara/selector/regexp_disassembler.rb
+++ b/lib/capybara/selector/regexp_disassembler.rb
@@ -28,6 +28,10 @@ module Capybara
     private
 
       def remove_and_covered(strings)
+        # delete_if is documented to modify the array after every block iteration - this doesn't appear to be true
+        # uniq the strings to prevent identical strings from removing each other
+        strings.uniq!
+
         # If we have "ab" and "abcd" required - only need to check for "abcd"
         strings.delete_if do |sub_string|
           strings.any? do |cover_string|
@@ -65,8 +69,12 @@ module Capybara
         exp.quantifier&.min || 1
       end
 
+      def max_repeat(exp)
+        exp.quantifier&.max || 1
+      end
+
       def fixed_repeat?(exp)
-        min_repeat(exp) == (exp.quantifier&.max || 1)
+        min_repeat(exp) == max_repeat(exp)
       end
 
       def optional?(exp)
@@ -97,9 +105,10 @@ module Capybara
         end
       end
 
-      def extract_strings(expression, strings = [], alternation: false)
+      def extract_strings(expression, alternation: false)
+        strings = []
         expression.each do |exp| # rubocop:disable Metrics/BlockLength
-          if optional?(exp) && !(alternation && zero_or_one?(exp))
+          if optional?(exp) && !alternation
             strings.push(nil)
             next
           end
@@ -115,39 +124,33 @@ module Capybara
           end
 
           if exp.terminal?
-            case exp.type
-            when :literal
-              if zero_or_one?(exp)
-                strings.push(Set.new([[''], [exp.text]]))
-                next
-              else
-                strings.push(exp.text * min_repeat(exp))
-              end
-            when :escape
-              if zero_or_one?(exp)
-                strings.push(Set.new([[''], [exp.text]]))
-                next
-              else
-                strings.push(exp.char * min_repeat(exp))
-              end
+            text = case exp.type
+            when :literal then exp.text
+            when :escape then exp.char
             else
               strings.push(nil)
+              next
             end
-          elsif alternation && zero_or_one?(exp)
+
+            if optional?(exp)
+              strings.push(Set.new([[''], [text]]))
+              strings.push(nil) unless max_repeat(exp) == 1
+              next
+            else
+              strings.push(text * min_repeat(exp))
+            end
+          elsif optional?(exp)
             strings.push(Set.new([[''], extract_strings(exp, alternation: true)]))
+            strings.push(nil) unless max_repeat(exp) == 1
             next
           else
-            min_repeat(exp).times { extract_strings(exp, strings, alternation: alternation) }
+            min_repeat(exp).times { strings.concat extract_strings(exp, alternation: alternation) }
           end
           strings.push(nil) unless fixed_repeat?(exp)
         end
         strings
       end
 
-      def zero_or_one?(exp)
-        exp.quantity == [0, 1]
-      end
-
       def alternative_strings(expression)
         alternatives = expression.alternatives.map { |sub_exp| extract_strings(sub_exp, alternation: true) }
         if alternatives.all?(&:any?)
diff --git a/spec/regexp_dissassembler_spec.rb b/spec/regexp_dissassembler_spec.rb
index 542555f4..a0ab55d8 100644
--- a/spec/regexp_dissassembler_spec.rb
+++ b/spec/regexp_dissassembler_spec.rb
@@ -124,7 +124,12 @@ RSpec.describe Capybara::Selector::RegexpDisassembler do
       /cd(ef|gh)?ij/ => %w[cd ij],
       /cd(ef|gh)+ij/ => %w[cd ij],
       /cd(ef|gh){2}ij/ => %w[cd ij],
-      /(cd(ef|g*))/ => %w[cd]
+      /(cd(ef|g*))/ => %w[cd],
+      /ab(cd){0,2}ef/ => %w[ab ef],
+      /ab(cd){0,1}ef/ => %w[ab ef],
+      /ab(cd|cd)ef/ => %w[ab ef],
+      /ab(cd|cd)?ef/ => %w[ab ef],
+      /ab\\?cd/ => %w[ab cd]
     }.each do |regexp, expected|
       expect(Capybara::Selector::RegexpDisassembler.new(regexp).substrings).to eq expected
     end
@@ -154,7 +159,12 @@ RSpec.describe Capybara::Selector::RegexpDisassembler do
       /(abc)?(d|e)/ => [%w[d], %w[e]],
       /(abc*de)?(d|e)/ => [%w[d], %w[e]],
       /(abc*de)?(d|e?)/ => [],
-      /(abc)?(d|e?)/ => []
+      /(abc)?(d|e?)/ => [],
+      /ab(cd){0,2}ef/ => [%w[ab ef]],
+      /ab(cd){0,1}ef/ => [%w[abef], %w[abcdef]],
+      /ab(cd|cd)ef/ => [%w[abcdef]],
+      /ab(cd|cd)?ef/ => [%w[abef], %w[abcdef]],
+      /ab\\?cd/ => [%w[abcd], %w[ab\cd]]
     )
   end