Fix xpath parsing xpath that has string literal containing parentheses and brackets

lib/rexml/parsers/xpathparser.rb

@@ -19,9 +19,7 @@ def namespaces=( namespaces )
       end
 
       def parse path
-        path = path.dup
-        path.gsub!(/([\(\[])\s+/, '\1') # Strip ignorable spaces
-        path.gsub!( /\s+([\]\)])/, '\1')
+        path = strip_ignorable_spaces(path)
         parsed = []
         rest = OrExpr(path, parsed)
         if rest
@@ -33,6 +31,20 @@ def parse path
         parsed
       end
 
+      def strip_ignorable_spaces(path)
+        # Safely do `path.gsub(/([\(\[])\s+/, '\1').gsub( /\s+([\]\)])/, '\1')`
+        # without modifying spaces inside string literals.
+        quote = nil
+        path.gsub(/([\(\[])\s+|\s+([\]\)])|(['"])/) do
+          if quote
+            quote = nil if $3 == quote
+            $&
+          else
+            $1 || $2 || (quote = $3)
+          end
+        end
+      end
+
       def predicate path
         parsed = []
         Predicate( "[#{path}]", parsed )
@@ -678,12 +690,20 @@ def get_group string
         depth = 0
         st = string[0,1]
         en = (st == "(" ? ")" : "]")
+        quote = nil
         begin
-          case string[ind,1]
-          when st
-            depth += 1
-          when en
-            depth -= 1
+          if quote
+            # ignore () [] inside quotes
+            quote = nil if string[ind] == quote
+          else
+            case string[ind]
+            when st
+              depth += 1
+            when en
+              depth -= 1
+            when '"', "'"
+              quote = string[ind]
+            end
           end
           ind += 1
         end while depth > 0 and ind < string.length

test/xpath/test_base.rb

@@ -803,6 +803,36 @@ def test_spaces
                    match.call('/ a / child:: c [( @id )] /'))
     end
 
+    def test_space_inside_xpath
+      parser = Parsers::XPathParser.new
+      assert_equal(
+        parser.parse('/a/b[string-length("1")<(2+3)]/c'),
+        parser.parse(' / a / b [ string-length( "1" ) < ( 2 + 3 ) ] / c '),
+      )
+      assert_equal(
+        parser.parse('//processing-instruction("a")'),
+        parser.parse('//processing-instruction( "a" )'),
+      )
+    end
+
+    def test_space_paren_brace_inside_xpath_string
+      doc = Document.new(<<~XML)
+        <a>
+          <b id=" [ ' 1 ) "/>
+          <b id=' ( " 2 ] '/>
+        </a>
+      XML
+
+      assert_equal(
+        [" [ ' 1 ) "],
+        REXML::XPath.match(doc, "/a/b[@id=\" [ ' 1 ) \"]").map { |e| e.attributes['id'] }
+      )
+      assert_equal(
+        [' ( " 2 ] '],
+        REXML::XPath.match(doc, "/a/b[@id=' ( \" 2 ] ']").map { |e| e.attributes['id'] }
+      )
+    end
+
     def test_text_nodes
       #  source = "<root>
       #<child/>