From f962890a928b566c0f5ca7fdff5ef4ce19207e65 Mon Sep 17 00:00:00 2001
From: Blaž Hrastnik <blaz.hrast@gmail.com>
Date: Thu, 9 Jul 2015 23:46:54 +0200
Subject: Implement Module#prepend.

---
 include/mruby/class.h |  1 +
 src/class.c           | 67 +++++++++++++++++++++++++++++++++++++++++++++++++--
 test/t/module.rb      | 33 +++++++++++++++++++++++++
 3 files changed, 99 insertions(+), 2 deletions(-)

diff --git a/include/mruby/class.h b/include/mruby/class.h
index 9d5260a24..60310ae9d 100644
--- a/include/mruby/class.h
+++ b/include/mruby/class.h
@@ -16,6 +16,7 @@ struct RClass {
   struct iv_tbl *iv;
   struct kh_mt *mt;
   struct RClass *super;
+  struct RClass *origin;
 };
 
 #define mrb_class_ptr(v)    ((struct RClass*)(mrb_ptr(v)))
diff --git a/src/class.c b/src/class.c
index 8a9fdaca6..3b1ea2321 100644
--- a/src/class.c
+++ b/src/class.c
@@ -194,6 +194,7 @@ define_class(mrb_state *mrb, mrb_sym name, struct RClass *super, struct RClass *
 
   if (mrb_const_defined_at(mrb, mrb_obj_value(outer), name)) {
     c = class_from_sym(mrb, outer, name);
+    c = c->origin;
     if (super && mrb_class_real(c->super) != super) {
       mrb_raisef(mrb, E_TYPE_ERROR, "superclass mismatch for Class %S (%S not %S)",
                  mrb_sym2str(mrb, name),
@@ -763,12 +764,13 @@ boot_defclass(mrb_state *mrb, struct RClass *super)
   else {
     c->super = mrb->object_class;
   }
+  c->origin = c;
   c->mt = kh_init(mt, mrb);
   return c;
 }
 
-MRB_API void
-mrb_include_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
+MRB_API inline void
+include_module_at(mrb_state *mrb, struct RClass *c, struct RClass *m, int search_super)
 {
   struct RClass *ins_pos;
 
@@ -782,6 +784,7 @@ mrb_include_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
     }
     while (p) {
       if (c != p && p->tt == MRB_TT_CLASS) {
+        if (!search_super) break;
         superclass_seen = 1;
       }
       else if (p->mt == m->mt) {
@@ -810,6 +813,63 @@ mrb_include_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
   }
 }
 
+MRB_API void
+mrb_include_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
+{
+  include_module_at(mrb, c, m, FALSE);
+}
+
+MRB_API void
+mrb_prepend_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
+{
+  struct RClass *origin;
+  int changed = 0;
+
+  origin = c->origin;
+  if (origin == c) {
+    origin = (struct RClass*)mrb_obj_alloc(mrb, MRB_TT_ICLASS, c);
+    //OBJ_WB_UNPROTECT(origin); /* TODO: conservative shading. Need more survey. */
+    origin->super = c->super;
+    c->super = origin;
+    c->origin = origin;
+    origin->mt = c->mt;
+    c->mt = kh_init(mt, mrb);
+  }
+  include_module_at(mrb, c, m, FALSE); // changed =
+  if (changed) {
+    //rb_vm_check_redefinition_by_prepend(klass);
+  }
+}
+
+static mrb_value
+mrb_mod_prepend_features(mrb_state *mrb, mrb_value mod)
+{
+  mrb_value klass;
+
+  mrb_check_type(mrb, mod, MRB_TT_MODULE);
+  mrb_get_args(mrb, "C", &klass);
+  mrb_prepend_module(mrb, mrb_class_ptr(klass), mrb_class_ptr(mod));
+  return mod;
+}
+
+static mrb_value
+mrb_mod_prepend(mrb_state *mrb, mrb_value klass)
+{
+  mrb_value *argv;
+  mrb_int argc, i;
+
+  mrb_get_args(mrb, "*", &argv, &argc);
+  for (i=0; i<argc; i++) {
+    mrb_check_type(mrb, argv[i], MRB_TT_MODULE);
+  }
+  while (argc--) {
+    mrb_funcall(mrb, argv[argc], "prepend_features", 1, klass);
+    mrb_funcall(mrb, argv[argc], "prepended", 1, klass);
+  }
+
+  return klass;
+}
+
 static mrb_value
 mrb_mod_append_features(mrb_state *mrb, mrb_value mod)
 {
@@ -2090,6 +2150,9 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_method(mrb, mod, "class_variable_set",      mrb_mod_cvar_set,         MRB_ARGS_REQ(2)); /* 15.2.2.4.18 */
   mrb_define_method(mrb, mod, "extend_object",           mrb_mod_extend_object,    MRB_ARGS_REQ(1)); /* 15.2.2.4.25 */
   mrb_define_method(mrb, mod, "extended",                mrb_bob_init,             MRB_ARGS_REQ(1)); /* 15.2.2.4.26 */
+  mrb_define_method(mrb, mod, "prepend",                 mrb_mod_prepend,          MRB_ARGS_ANY());
+  mrb_define_method(mrb, mod, "prepended",               mrb_bob_init,             MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, mod, "prepend_features",        mrb_mod_prepend_features, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, mod, "include",                 mrb_mod_include,          MRB_ARGS_ANY());  /* 15.2.2.4.27 */
   mrb_define_method(mrb, mod, "include?",                mrb_mod_include_p,        MRB_ARGS_REQ(1)); /* 15.2.2.4.28 */
   mrb_define_method(mrb, mod, "append_features",         mrb_mod_append_features,  MRB_ARGS_REQ(1)); /* 15.2.2.4.10 */
diff --git a/test/t/module.rb b/test/t/module.rb
index ecb969475..9faaf6e2c 100644
--- a/test/t/module.rb
+++ b/test/t/module.rb
@@ -474,6 +474,39 @@ end
 
 # Not ISO specified
 
+assert('Module#prepend') do
+  module M0
+    def m1; [:M0] end
+  end
+  module M1
+    def m1; [:M1, super, :M1] end
+  end
+  module M2
+    def m1; [:M2, super, :M2] end
+  end
+  M3 = Module.new do
+    def m1; [:M3, super, :M3] end
+  end
+  module M4
+    def m1; [:M4, super, :M4] end
+  end
+
+  class C0
+    include M0
+    prepend M1
+    def m1; [:C0, super, :C0] end
+  end
+  class C1 < C0
+    prepend M2, M3
+    include M4
+    def m1; [:C1, super, :C1] end
+  end
+
+  obj = C1.new
+  expected = [:M2,[:M3,[:C1,[:M4,[:M1,[:C0,[:M0],:C0],:M1],:M4],:C1],:M3],:M2]
+  assert_equal(expected, obj.m1)
+end
+
 assert('Module#to_s') do
   module Test4to_sModules
   end
-- 
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