From 9b7fe0a25012d615f1cae8da1f5c444f61ffb7c7 Mon Sep 17 00:00:00 2001
From: mame <mame@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 19 Jan 2018 10:48:08 +0000
Subject: ext/ripper: Introduce a simple DSL for ripper.y code generation

Currently, parse.y actions are hard to read and write because the code
has double meaning (for core parser and for ripper).  I think that, if
it is easy to write ripper's code shortly and simply, the double meaning
trick is not needed.

For the sake, this change adds a simple DSL for ripper's code.  For
example, in parse.y, we can write:

    /*% ripper: stmts_add(stmts_new, void_stmt) %*/

instead of:

    $$ = dispatch2(stmts_add, dispatch0(stmts_new),
                   dispatch0(void_stmt));

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61952 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ext/ripper/tools/dsl.rb      | 46 ++++++++++++++++++++++++++++++++++++++++++++
 ext/ripper/tools/generate.rb |  9 +++++++++
 ext/ripper/tools/preproc.rb  |  4 ++++
 3 files changed, 59 insertions(+)
 create mode 100644 ext/ripper/tools/dsl.rb

(limited to 'ext/ripper/tools')

diff --git a/ext/ripper/tools/dsl.rb b/ext/ripper/tools/dsl.rb
new file mode 100644
index 0000000000..e321019d7e
--- /dev/null
+++ b/ext/ripper/tools/dsl.rb
@@ -0,0 +1,46 @@
+# Simple DSL implementation for Ripper code generation
+#
+# input: /*% ripper: stmts_add(stmts_new, void_stmt) %*/
+# output: $$ = dispatch2(stmts_add, dispatch0(stmts_new), dispatch0(void_stmt))
+
+class DSL
+  def initialize(code, options)
+    @events = {}
+    @error = options.include?("error")
+    @brace = options.include?("brace")
+
+    # create $1 == "$1", $2 == "$2", ...
+    re, s = "", ""
+    1.upto(9) do |n|
+      re << "(..)"
+      s << "$#{ n }"
+    end
+    /#{ re }/ =~ s
+
+    @code = eval(code)
+  end
+
+  attr_reader :events
+
+  undef lambda
+  undef hash
+  undef class
+
+  def generate
+    s = "$$"
+    s = "\t\t\t#{ s } = #@code;"
+    s << "ripper_error(p);" if @error
+    s = "{#{ s }}" if @brace
+    s
+  end
+
+  def method_missing(*args)
+    if args.first =~ /\A_/
+      "#{ $' }(#{ args.drop(1).join(", ") })"
+    else
+      @events[args.first.to_s] = args.size - 1
+      "dispatch#{ args.size - 1 }(#{ args.join(", ") })"
+    end
+  end
+end
+
diff --git a/ext/ripper/tools/generate.rb b/ext/ripper/tools/generate.rb
index cf24f1398d..883e6ef2df 100755
--- a/ext/ripper/tools/generate.rb
+++ b/ext/ripper/tools/generate.rb
@@ -135,6 +135,8 @@ def check_arity(h)
   abort if invalid
 end
 
+require_relative "dsl"
+
 def read_ids1_with_locations(path)
   h = {}
   File.open(path) {|f|
@@ -144,6 +146,13 @@ def read_ids1_with_locations(path)
       line.scan(/\bdispatch(\d)\((\w+)/) do |arity, event|
         (h[event] ||= []).push [f.lineno, arity.to_i]
       end
+      if line =~ %r</\*% *ripper(?:\[(.*?)\])?: *(.*?) *%\*/>
+        gen = DSL.new($2, ($1 || "").split(","))
+        gen.generate
+        gen.events.each do |event, arity|
+          (h[event] ||= []).push [f.lineno, arity.to_i]
+        end
+      end
     end
   }
   h
diff --git a/ext/ripper/tools/preproc.rb b/ext/ripper/tools/preproc.rb
index 8b68579164..560a82e54f 100755
--- a/ext/ripper/tools/preproc.rb
+++ b/ext/ripper/tools/preproc.rb
@@ -72,9 +72,13 @@ def prelude(f, out)
   end
 end
 
+require_relative "dsl"
+
 def grammar(f, out)
   while line = f.gets
     case line
+    when %r</\*% *ripper(?:\[(.*?)\])?: *(.*?) *%\*/>
+      out << DSL.new($2, ($1 || "").split(",")).generate << $/
     when %r</\*%%%\*/>
       out << '#if 0' << $/
     when %r</\*%c%\*/>
-- 
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