From 6d39050e1e4ee7ce3c93492cd58df52caaaa256b Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <Dylan.Smith@shopify.com>
Date: Mon, 19 Oct 2020 11:32:18 -0400
Subject: [PATCH 1/3] Use a case statement in Liquid::Parser#expression

---
 lib/liquid/parser.rb | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/lib/liquid/parser.rb b/lib/liquid/parser.rb
index e038037..5b38eac 100644
--- a/lib/liquid/parser.rb
+++ b/lib/liquid/parser.rb
@@ -46,16 +46,14 @@ module Liquid
       tok[0] == type
     end
 
-    SINGLE_TOKEN_EXPRESSION_TYPES = [:string, :number].freeze
-    private_constant :SINGLE_TOKEN_EXPRESSION_TYPES
-
     def expression
       token = @tokens[@p]
-      if token[0] == :id
+      case token[0]
+      when :id
         variable_signature
-      elsif SINGLE_TOKEN_EXPRESSION_TYPES.include?(token[0])
+      when :string, :number
         consume
-      elsif token.first == :open_round
+      when :open_round
         consume
         first = expression
         consume(:dotdot)

From 420a1c79e1010f9184ecad0692a72f3bee023e08 Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <Dylan.Smith@shopify.com>
Date: Mon, 19 Oct 2020 12:10:32 -0400
Subject: [PATCH 2/3] Refactor variable lookup strict parsing to reduce
 coupling on dot lookup

---
 lib/liquid/parser.rb | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/lib/liquid/parser.rb b/lib/liquid/parser.rb
index 5b38eac..b43576e 100644
--- a/lib/liquid/parser.rb
+++ b/lib/liquid/parser.rb
@@ -50,7 +50,8 @@ module Liquid
       token = @tokens[@p]
       case token[0]
       when :id
-        variable_signature
+        str = consume
+        str << variable_lookups
       when :string, :number
         consume
       when :open_round
@@ -76,16 +77,19 @@ module Liquid
       str
     end
 
-    def variable_signature
-      str = consume(:id)
-      while look(:open_square)
-        str << consume
-        str << expression
-        str << consume(:close_square)
-      end
-      if look(:dot)
-        str << consume
-        str << variable_signature
+    def variable_lookups
+      str = +""
+      loop do
+        if look(:open_square)
+          str << consume
+          str << expression
+          str << consume(:close_square)
+        elsif look(:dot)
+          str << consume
+          str << consume(:id)
+        else
+          break
+        end
       end
       str
     end

From 46fd63da5f149f5c6485dfc26982a9e2b5651a48 Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <Dylan.Smith@shopify.com>
Date: Mon, 19 Oct 2020 12:07:39 -0400
Subject: [PATCH 3/3] Fix strict parsing of find variable with a name
 expression

---
 lib/liquid/parser.rb              | 5 +++++
 test/integration/variable_test.rb | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/lib/liquid/parser.rb b/lib/liquid/parser.rb
index b43576e..609601a 100644
--- a/lib/liquid/parser.rb
+++ b/lib/liquid/parser.rb
@@ -52,6 +52,11 @@ module Liquid
       when :id
         str = consume
         str << variable_lookups
+      when :open_square
+        str = consume
+        str << expression
+        str << consume(:close_square)
+        str << variable_lookups
       when :string, :number
         consume
       when :open_round
diff --git a/test/integration/variable_test.rb b/test/integration/variable_test.rb
index 45268bd..168f43a 100644
--- a/test/integration/variable_test.rb
+++ b/test/integration/variable_test.rb
@@ -95,4 +95,8 @@ class VariableTest < Minitest::Test
   def test_render_symbol
     assert_template_result('bar', '{{ foo }}', 'foo' => :bar)
   end
+
+  def test_dynamic_find_var
+    assert_template_result('bar', '{{ [key] }}', 'key' => 'foo', 'foo' => 'bar')
+  end
 end