From 6eb1b12a9b9c61288905e4252afcf9c841a2f46e Mon Sep 17 00:00:00 2001
From: Ian Ker-Seymer <ian.kerseymer@shopify.com>
Date: Wed, 23 Oct 2024 11:52:43 -0400
Subject: [PATCH] Fix bug when parsing negative numbers

---
 lib/liquid/lexer.rb                 | 24 ++++++++++++++++++++----
 performance/unit/lexer_benchmark.rb | 13 +++++++++++++
 test/unit/lexer_unit_test.rb        | 10 ++++++++++
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/lib/liquid/lexer.rb b/lib/liquid/lexer.rb
index cc6db0ad..9c392fad 100644
--- a/lib/liquid/lexer.rb
+++ b/lib/liquid/lexer.rb
@@ -143,10 +143,18 @@ module Liquid
       table["-".ord] = DASH
     end
 
+    NUMBER_TABLE = [].tap do |table|
+      "0".upto("9") do |c|
+        table[c.ord] = true
+      end
+      table.freeze
+    end
+
     def initialize(input)
       @ss = StringScanner.new(input)
     end
 
+    # rubocop:disable Metrics/BlockNesting
     def tokenize
       @output = []
 
@@ -159,16 +167,24 @@ module Liquid
 
         if (special = SPECIAL_TABLE[peeked])
           @ss.scan_byte
+          # Special case for ".."
           if special == DOT && @ss.peek_byte == DOT_ORD
             @ss.scan_byte
             @output << DOTDOT
+          elsif special == DASH
+            # Special case for negative numbers
+            if NUMBER_TABLE[@ss.peek_byte]
+              @ss.pos -= 1
+              @output << [:number, @ss.scan(NUMBER_LITERAL)]
+            else
+              @output << special
+            end
           else
             @output << special
           end
         elsif (sub_table = COMPARISON_JUMP_TABLE[peeked])
           @ss.scan_byte
-          next_peeked = @ss.peek_byte
-          if (found = sub_table[next_peeked])
+          if (found = sub_table[@ss.peek_byte])
             @output << found
             @ss.scan_byte
           else
@@ -178,18 +194,18 @@ module Liquid
           type, pattern = NEXT_MATCHER_JUMP_TABLE[peeked]
 
           if type && (t = @ss.scan(pattern))
-            # rubocop:disable Metrics/BlockNesting
+            # Special case for "contains"
             @output << if type == :id && t == "contains"
               COMPARISON_CONTAINS
             else
               [type, t]
             end
-            # rubocop:enable Metrics/BlockNesting
           else
             raise SyntaxError, "Unexpected character #{peeked.chr}"
           end
         end
       end
+      # rubocop:enable Metrics/BlockNesting
 
       @output << EOS
     end
diff --git a/performance/unit/lexer_benchmark.rb b/performance/unit/lexer_benchmark.rb
index 83a64417..2faa1f68 100644
--- a/performance/unit/lexer_benchmark.rb
+++ b/performance/unit/lexer_benchmark.rb
@@ -26,8 +26,21 @@ EXPRESSIONS = [
   "foo != 'bar'",
   "'foo' contains 'bar'",
   '234089',
+  "foo | default: -1",
 ]
 
+EXPRESSIONS.each do |expr|
+  lexer_1_result = Liquid::Lexer1.new(expr).tokenize
+  lexer_2_result = Liquid::Lexer2.new(expr).tokenize
+
+  next if lexer_1_result == lexer_2_result
+
+  warn "Lexer1 and Lexer2 results are different for expression: #{expr}"
+  warn "expected: #{lexer_1_result}"
+  warn "got: #{lexer_2_result}"
+  abort
+end
+
 Benchmark.ips do |x|
   x.config(time: 10, warmup: 5)
 
diff --git a/test/unit/lexer_unit_test.rb b/test/unit/lexer_unit_test.rb
index ad4a5bd3..363740b4 100644
--- a/test/unit/lexer_unit_test.rb
+++ b/test/unit/lexer_unit_test.rb
@@ -50,4 +50,14 @@ class LexerUnitTest < Minitest::Test
       Lexer.new("%").tokenize
     end
   end
+
+  def test_negative_numbers
+    tokens = Lexer.new("foo | default: -1").tokenize
+    assert_equal([[:id, 'foo'], [:pipe, '|'], [:id, 'default'], [:colon, ":"], [:number, '-1'], [:end_of_string]], tokens)
+  end
+
+  def test_greater_than_two_digits
+    tokens = Lexer.new("foo > 12").tokenize
+    assert_equal([[:id, 'foo'], [:comparison, '>'], [:number, '12'], [:end_of_string]], tokens)
+  end
 end