From 1667c1180e8f99eb4c515053c009fba74741e25c Mon Sep 17 00:00:00 2001
From: Watson <watson1978@gmail.com>
Date: Sat, 12 Mar 2022 01:41:12 +0900
Subject: [PATCH] Use start_with? and end_with? to detect SQUARE_BRAKET
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## Test code
```ruby
require 'benchmark/ips'

SQUARE_BRACKETED = /\A\[(.*)\]\z/m
markup = "[product.catchall]"

Benchmark.ips do |x|
  x.report("SQUARE_BRACKETED") {
    if markup =~ SQUARE_BRACKETED
      Regexp.last_match(1)
    end
  }
  x.report("start/end_with?") {
    if markup&.start_with?('[') && markup&.end_with?(']')
      markup[1..-2]
    end
  }

  x.compare!
end
```

## Result
```
Warming up --------------------------------------
    SQUARE_BRACKETED   261.300k i/100ms
     start/end_with?   548.813k i/100ms
Calculating -------------------------------------
    SQUARE_BRACKETED      2.632M (± 0.6%) i/s -     13.326M in   5.064085s
     start/end_with?      5.471M (± 0.5%) i/s -     27.441M in   5.015770s

Comparison:
     start/end_with?:  5470994.1 i/s
    SQUARE_BRACKETED:  2631642.3 i/s - 2.08x  (± 0.00) slower
```
---
 lib/liquid/variable_lookup.rb | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/liquid/variable_lookup.rb b/lib/liquid/variable_lookup.rb
index 9d5dba68..775b002e 100644
--- a/lib/liquid/variable_lookup.rb
+++ b/lib/liquid/variable_lookup.rb
@@ -2,8 +2,7 @@
 
 module Liquid
   class VariableLookup
-    SQUARE_BRACKETED = /\A\[(.*)\]\z/m
-    COMMAND_METHODS  = ['size', 'first', 'last'].freeze
+    COMMAND_METHODS = ['size', 'first', 'last'].freeze
 
     attr_reader :name, :lookups
 
@@ -15,8 +14,8 @@ module Liquid
       lookups = markup.scan(VariableParser)
 
       name = lookups.shift
-      if name =~ SQUARE_BRACKETED
-        name = Expression.parse(Regexp.last_match(1))
+      if name&.start_with?('[') && name&.end_with?(']')
+        name = Expression.parse(name[1..-2])
       end
       @name = name
 
@@ -25,8 +24,8 @@ module Liquid
 
       @lookups.each_index do |i|
         lookup = lookups[i]
-        if lookup =~ SQUARE_BRACKETED
-          lookups[i] = Expression.parse(Regexp.last_match(1))
+        if lookup&.start_with?('[') && lookup&.end_with?(']')
+          lookups[i] = Expression.parse(lookup[1..-2])
         elsif COMMAND_METHODS.include?(lookup)
           @command_flags |= 1 << i
         end