From 0b8f35dd9ca6d1ae72e6021e64688e2d88b84537 Mon Sep 17 00:00:00 2001
From: Jack Danger Canty <jackdanger@squareup.com>
Date: Sun, 3 Aug 2014 15:23:56 -0700
Subject: Using no_result_var in Journey's parser generator

Previously the generated parser had an intermediate local variable
`result` that really useful if you're building up a stateful object but
Journey always discards the result argument to the reduce functions.

This produces a simpler parser for anybody who actually wants to read
the thing.

Sadly, there's no real performance speedup with this change.
---
 actionpack/lib/action_dispatch/journey/parser.rb | 54 ++++++++++--------------
 actionpack/lib/action_dispatch/journey/parser.y  | 22 +++++-----
 2 files changed, 33 insertions(+), 43 deletions(-)

diff --git a/actionpack/lib/action_dispatch/journey/parser.rb b/actionpack/lib/action_dispatch/journey/parser.rb
index d129ba7e16..9012297400 100644
--- a/actionpack/lib/action_dispatch/journey/parser.rb
+++ b/actionpack/lib/action_dispatch/journey/parser.rb
@@ -86,7 +86,7 @@ racc_token_table = {
 
 racc_nt_base = 10
 
-racc_use_result_var = true
+racc_use_result_var = false
 
 Racc_arg = [
   racc_action_table,
@@ -133,14 +133,12 @@ Racc_debug_parser = false
 
 # reduce 0 omitted
 
-def _reduce_1(val, _values, result)
- result = Cat.new(val.first, val.last) 
-    result
+def _reduce_1(val, _values)
+ Cat.new(val.first, val.last)
 end
 
-def _reduce_2(val, _values, result)
- result = val.first 
-    result
+def _reduce_2(val, _values)
+ val.first
 end
 
 # reduce 3 omitted
@@ -151,24 +149,20 @@ end
 
 # reduce 6 omitted
 
-def _reduce_7(val, _values, result)
- result = Group.new(val[1]) 
-    result
+def _reduce_7(val, _values)
+ Group.new(val[1])
 end
 
-def _reduce_8(val, _values, result)
- result = Or.new([val.first, val.last]) 
-    result
+def _reduce_8(val, _values)
+ Or.new([val.first, val.last])
 end
 
-def _reduce_9(val, _values, result)
- result = Or.new([val.first, val.last]) 
-    result
+def _reduce_9(val, _values)
+ Or.new([val.first, val.last])
 end
 
-def _reduce_10(val, _values, result)
- result = Star.new(Symbol.new(val.last)) 
-    result
+def _reduce_10(val, _values)
+ Star.new(Symbol.new(val.last))
 end
 
 # reduce 11 omitted
@@ -179,27 +173,23 @@ end
 
 # reduce 14 omitted
 
-def _reduce_15(val, _values, result)
- result = Slash.new('/') 
-    result
+def _reduce_15(val, _values)
+ Slash.new('/')
 end
 
-def _reduce_16(val, _values, result)
- result = Symbol.new(val.first) 
-    result
+def _reduce_16(val, _values)
+ Symbol.new(val.first)
 end
 
-def _reduce_17(val, _values, result)
- result = Literal.new(val.first) 
-    result
+def _reduce_17(val, _values)
+ Literal.new(val.first)
 end
 
-def _reduce_18(val, _values, result)
- result = Dot.new(val.first) 
-    result
+def _reduce_18(val, _values)
+ Dot.new(val.first)
 end
 
-def _reduce_none(val, _values, result)
+def _reduce_none(val, _values)
   val[0]
 end
 
diff --git a/actionpack/lib/action_dispatch/journey/parser.y b/actionpack/lib/action_dispatch/journey/parser.y
index 0ead222551..d3f7c4d765 100644
--- a/actionpack/lib/action_dispatch/journey/parser.y
+++ b/actionpack/lib/action_dispatch/journey/parser.y
@@ -1,11 +1,11 @@
 class ActionDispatch::Journey::Parser
-
+  options no_result_var
 token SLASH LITERAL SYMBOL LPAREN RPAREN DOT STAR OR
 
 rule
   expressions
-    : expression expressions  { result = Cat.new(val.first, val.last) }
-    | expression              { result = val.first }
+    : expression expressions  { Cat.new(val.first, val.last) }
+    | expression              { val.first }
     | or
     ;
   expression
@@ -14,14 +14,14 @@ rule
     | star
     ;
   group
-    : LPAREN expressions RPAREN { result = Group.new(val[1]) }
+    : LPAREN expressions RPAREN { Group.new(val[1]) }
     ;
   or
-    : expression OR expression { result = Or.new([val.first, val.last]) }
-    | expression OR or { result = Or.new([val.first, val.last]) }
+    : expression OR expression { Or.new([val.first, val.last]) }
+    | expression OR or { Or.new([val.first, val.last]) }
     ;
   star
-    : STAR       { result = Star.new(Symbol.new(val.last)) }
+    : STAR       { Star.new(Symbol.new(val.last)) }
     ;
   terminal
     : symbol
@@ -30,16 +30,16 @@ rule
     | dot
     ;
   slash
-    : SLASH              { result = Slash.new('/') }
+    : SLASH              { Slash.new('/') }
     ;
   symbol
-    : SYMBOL             { result = Symbol.new(val.first) }
+    : SYMBOL             { Symbol.new(val.first) }
     ;
   literal
-    : LITERAL            { result = Literal.new(val.first) }
+    : LITERAL            { Literal.new(val.first) }
     ;
   dot
-    : DOT                { result = Dot.new(val.first) }
+    : DOT                { Dot.new(val.first) }
     ;
 
 end
-- 
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