Add ExpressionParser and ExpressionConsumer

test/unit/expression_parser_test.rb

@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class ExpressionParserTest < Minitest::Test
+  include Liquid
+
+  def test_parse_returns_nil_for_empty_string
+    result = ExpressionParser.parse('', parse_context)
+    assert_nil(result)
+  end
+
+  def test_parse_returns_nil_for_whitespace_only
+    result = ExpressionParser.parse('   ', parse_context)
+    assert_nil(result)
+  end
+
+  def test_parse_raises_on_extra_tokens_after_expression
+    error = assert_raises(SyntaxError) do
+      ExpressionParser.parse('foo bar', parse_context)
+    end
+    assert_match(/Expected end_of_string but found id/, error.message)
+  end
+
+  def test_parse_string_literal_with_double_quotes
+    result = ExpressionParser.parse('"hello"', parse_context)
+    assert_equal('hello', result)
+  end
+
+  def test_parse_string_literal_with_single_quotes
+    result = ExpressionParser.parse("'world'", parse_context)
+    assert_equal('world', result)
+  end
+
+  def test_parse_integer_literal
+    result = ExpressionParser.parse('42', parse_context)
+    assert_equal(42, result)
+  end
+
+  def test_parse_float_literal
+    result = ExpressionParser.parse('3.14', parse_context)
+    assert_equal(3.14, result)
+  end
+
+  def test_parse_nil_literal
+    result = ExpressionParser.parse('nil', parse_context)
+    assert_nil(result)
+  end
+
+  def test_parse_true_literal
+    result = ExpressionParser.parse('true', parse_context)
+    assert_equal(true, result)
+  end
+
+  def test_parse_simple_variable
+    result = ExpressionParser.parse('product', parse_context)
+    assert_kind_of(VariableLookup, result)
+    assert_equal('product', result.name)
+  end
+
+  def test_parse_variable_with_dot_lookup
+    result = ExpressionParser.parse('product.title', parse_context)
+    assert_kind_of(VariableLookup, result)
+    assert_equal('product', result.name)
+    assert_equal(['title'], result.lookups)
+  end
+
+  def test_parse_variable_with_bracket_lookup
+    result = ExpressionParser.parse('items[0]', parse_context)
+    assert_kind_of(VariableLookup, result)
+    assert_equal('items', result.name)
+    assert_equal(0, result.lookups[0])
+  end
+
+  def test_parse_range_with_integer_literals
+    result = ExpressionParser.parse('(1..5)', parse_context)
+    assert_kind_of(Range, result)
+    assert_equal(1..5, result)
+  end
+
+  def test_parse_range_with_variables
+    result = ExpressionParser.parse('(start..end)', parse_context)
+    assert_kind_of(RangeLookup, result)
+  end
+
+  def test_parse_validates_end_of_string
+    result = ExpressionParser.parse('foo', parse_context)
+    assert_kind_of(VariableLookup, result)
+  end
+
+  def test_parse_evaluates_correctly
+    result = ExpressionParser.parse('product.title', parse_context)
+    context = Context.new({ 'product' => { 'title' => 'My Title' } })
+    assert_equal('My Title', context.evaluate(result))
+  end
+
+  private
+
+  def parse_context
+    @parse_context ||= ParseContext.new(environment: Environment.build(error_mode: :rigid))
+  end
+end