Add support for parenthesized expressions

lib/liquid/parser.rb

@@ -100,7 +100,7 @@ module Liquid
       when :number
         number
       when :open_round
-        range_lookup
+        grouping_or_range_lookup
       else
         raise SyntaxError, "#{token} is not a valid expression"
       end
@@ -131,6 +131,19 @@ module Liquid
       VariableLookup.new(name, lookups, command_flags)
     end
 
+    # Parenthesized expressions are recursive
+    def grouping_or_range_lookup
+      consume(:open_round)
+      expr = expression
+      if consume?(:dotdot)
+        RangeLookup.create(expr, expression)
+      else
+        expr
+      end
+    ensure
+      consume(:close_round)
+    end
+
     def range_lookup
       consume(:open_round)
       first = expression

test/integration/assign_test.rb

@@ -35,13 +35,26 @@ class AssignTest < Minitest::Test
     )
   end
 
+  def test_assign_boolean_expression_assignment
+    assert_template_result(
+      'it rendered',
+      <<~LIQUID,
+        {%- assign should_render = a == 0 or (b == 1 and c == 2) -%}
+        {%- if should_render -%}
+          it rendered
+        {%- endif -%}
+      LIQUID
+      { 'b' => 1, 'c' => 2 },
+    )
+  end
+
   def test_assign_syntax_error
     assert_match_syntax_error(/assign/, '{% assign foo not values %}.')
   end
 
   def test_assign_throws_on_unsupported_syntax
     assert_match_syntax_error(
-      "Expected dotdot but found pipe",
+      "Expected close_round but found pipe",
       "{% assign foo = ('X' | downcase) %}",
     )
   end

test/integration/parsing_quirks_test.rb

@@ -35,11 +35,10 @@ class ParsingQuirksTest < Minitest::Test
     assert_raises(Liquid::SyntaxError) { Template.parse("{{test |a|b|}}") }
   end
 
-  def test_meaningless_parens_error
-    assert_raises(SyntaxError) do
-      markup = "a == 'foo' or (b == 'bar' and c == 'baz') or false"
-      Template.parse("{% if #{markup} %} YES {% endif %}")
-    end
+  def test_supported_parens
+    markup = "a == 'foo' or (b == 'bar' and c == 'baz') or false"
+    out = Template.parse("{% if #{markup} %} YES {% endif %}").render({ 'b' => 'bar', 'c' => 'baz' })
+    assert_equal(' YES ', out)
   end
 
   def test_unexpected_characters_syntax_error

test/unit/parser_unit_test.rb

@@ -98,12 +98,12 @@ class ParserUnitTest < Minitest::Test
     expr = p.expression
     assert(expr.is_a?(BinaryExpression))
     assert_equal('and', expr.operator)
-    assert_equal('==', expr.left_node.operator)
-    assert_equal('a', expr.left_node.left_node.name)
-    assert_equal('b', expr.left_node.right_node.name)
-    assert_equal('or', expr.right_node.operator)
-    assert_equal('c', expr.right_node.left_node.name)
-    assert_equal('d', expr.right_node.right_node.name)
+    assert_equal('==',  expr.left_node.operator)
+    assert_equal('a',   expr.left_node.left_node.name)
+    assert_equal('b',   expr.left_node.right_node.name)
+    assert_equal('or',  expr.right_node.operator)
+    assert_equal('c',   expr.right_node.left_node.name)
+    assert_equal('d',   expr.right_node.right_node.name)
   end
 
   def test_equality
@@ -197,6 +197,28 @@ class ParserUnitTest < Minitest::Test
     assert_equal('(hi[5].wat..old)', p.expression_string)
   end
 
+  def test_groupings_aka_parenthesized_expressions
+    # without the parens, this would be evaled as a and (b or c)
+    p = new_parser("(a and b) or c")
+    expr = p.expression
+    assert_equal('or', expr.operator)
+    assert_equal('and', expr.left_node.operator)
+    assert_equal('a', expr.left_node.left_node.name)
+    assert_equal('b', expr.left_node.right_node.name)
+    assert_equal('c', expr.right_node.name)
+  end
+
+  def test_groupings_can_be_used_to_hijack_operation_priority
+    # without parens would be parsed as `a and (b == c)`
+    p = new_parser("(a and b) == c")
+    expr = p.expression
+    assert_equal('==', expr.operator)
+    assert_equal('and', expr.left_node.operator)
+    assert_equal('a', expr.left_node.left_node.name)
+    assert_equal('b', expr.left_node.right_node.name)
+    assert_equal('c', expr.right_node.name)
+  end
+
   def test_argument_string
     p = new_parser("filter: hi.there[5], keyarg: 7")
     assert_equal('filter', p.consume(:id))