From a81aaf8158440dbd979faf6e7378edab4590713a Mon Sep 17 00:00:00 2001
From: Jack Danger Canty <jackdanger@squareup.com>
Date: Sat, 10 Aug 2013 22:59:12 -0700
Subject: [PATCH] Allowing binding to list its local variables

Before this patch:

    def get_all_local_variables(bind)
      lvars = bind.send(:local_variables)
      # `lvars` should equal [:x, :y], but equals [:bind, :lvars]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    get_all_local_variables(binding) # NameError: local variable `bind' not defined for #<Binding:0x0>

After this patch:

    def get_all_local_variables(bind)
      lvars = bind.local_variables
      # `lvars` equals [:x, :y]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    get_all_local_variables(binding) # => [1, 2]

bind.send(:local_variables) was a global method that used the current
stack frame regardless of binding. Now that we have
`Binding#local_variable_get` and `Binding#local_variable_set` the API
feels very strange without `Binding#local_variables` working similarly.
---
 proc.c                     | 53 ++++++++++++++++++++++++++++++++++++++++++++++
 test/ruby/test_variable.rb |  9 ++++++++
 2 files changed, 62 insertions(+)

diff --git a/proc.c b/proc.c
index 6fd3981..da9b7ac 100644
--- a/proc.c
+++ b/proc.c
@@ -444,6 +444,58 @@ check_local_id(VALUE bindval, volatile VALUE *pname)
 
 /*
  *  call-seq:
+ *     binding.local_variables -> Array
+ *
+ *  Returns the +symbol+ names of the binding's local variables
+ *
+ *	def foo
+ *  	  a = 1
+ *  	  2.times do |n|
+ *  	    binding.local_variables #=> [:a, :n]
+ *  	  end
+ *  	end
+ *
+ *  This method is short version of the following code.
+ *
+ *	binding.eval("local_variables")
+ *
+ */
+static VALUE
+bind_local_variables(VALUE bindval)
+{
+    VALUE ary = rb_ary_new();
+
+    const rb_binding_t *bind;
+    const rb_env_t *env;
+    VALUE envval;
+
+    GetBindingPtr(bindval, bind);
+
+    envval = bind->env;
+    GetEnvPtr(envval, env);
+
+    do {
+      const rb_iseq_t *iseq;
+      int i;
+      ID id;
+      iseq = env->block.iseq;
+
+      for (i=0; i<iseq->local_table_size; i++) {
+        id = iseq->local_table[i];
+        if (id) {
+          const char *vname = rb_id2name(id);
+          if (vname) {
+            rb_ary_push(ary, ID2SYM(id));
+          }
+        }
+      }
+    } while ((envval = env->prev_envval) != 0);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
  *     binding.local_variable_get(symbol) -> obj
  *
  *  Returns a +value+ of local variable +symbol+.
@@ -2697,6 +2749,7 @@ Init_Binding(void)
     rb_define_method(rb_cBinding, "clone", binding_clone, 0);
     rb_define_method(rb_cBinding, "dup", binding_dup, 0);
     rb_define_method(rb_cBinding, "eval", bind_eval, -1);
+    rb_define_method(rb_cBinding, "local_variables", bind_local_variables, 0);
     rb_define_method(rb_cBinding, "local_variable_get", bind_local_variable_get, 1);
     rb_define_method(rb_cBinding, "local_variable_set", bind_local_variable_set, 2);
     rb_define_method(rb_cBinding, "local_variable_defined?", bind_local_variable_defined_p, 1);
diff --git a/test/ruby/test_variable.rb b/test/ruby/test_variable.rb
index 32b3d61..9752ae3 100644
--- a/test/ruby/test_variable.rb
+++ b/test/ruby/test_variable.rb
@@ -83,6 +83,15 @@ class TestVariable < Test::Unit::TestCase
     end.call
   end
 
+  def _new_binding(bind)
+    this_should_not_be_in_bind = 2
+    assert_equal([:x], bind.local_variables)
+  end
+  def test_local_variables_from_other_method_binding
+    x = 1
+    _new_binding(binding)
+  end
+
   def test_global_variable_0
     assert_in_out_err(["-e", "$0='t'*1000;print $0"], "", /\At+\z/, [])
   end
-- 
1.8.1.3