class.c: call hook methods on method definitions; close #2339

- `Module#method_added`
- `BasicObject#singleton_method_added`

3 files changed, 52 insertions, 1 deletions

diff --git a/src/class.c b/src/class.c
index 11f4b3d29..8775ded3b 100644
--- a/src/class.c
+++ b/src/class.c
@@ -2505,6 +2505,22 @@ mrb_mod_method_defined(mrb_state *mrb, mrb_value mod)
   return mrb_bool_value(mrb_obj_respond_to(mrb, mrb_class_ptr(mod), id));
 }
 
+void
+mrb_method_added(mrb_state *mrb, struct RClass *c, mrb_sym mid)
+{
+  mrb_sym added;
+  mrb_value recv = mrb_obj_value(c);
+
+  if (c->tt == MRB_TT_SCLASS) {
+    added = MRB_SYM(singleton_method_added);
+    recv = mrb_iv_get(mrb, recv, MRB_SYM(__attached__));
+  }
+  else {
+    added = MRB_SYM(method_added);
+  }
+  mrb_funcall_id(mrb, recv, added, 1, mrb_symbol_value(mid));
+}
+
 mrb_value
 mrb_mod_define_method_m(mrb_state *mrb, struct RClass *c)
 {
@@ -2534,6 +2550,7 @@ mrb_mod_define_method_m(mrb_state *mrb, struct RClass *c)
   p->flags |= MRB_PROC_STRICT;
   MRB_METHOD_FROM_PROC(m, p);
   mrb_define_method_raw(mrb, c, mid, m);
+  mrb_method_added(mrb, c, mid);
   return mrb_symbol_value(mid);
 }
 
@@ -2892,6 +2909,7 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_method(mrb, bob, "__send__",                mrb_f_send,               MRB_ARGS_REQ(1)|MRB_ARGS_REST()|MRB_ARGS_BLOCK());  /* 15.3.1.3.5  */
   mrb_define_method(mrb, bob, "equal?",                  mrb_obj_equal_m,          MRB_ARGS_REQ(1)); /* 15.3.1.3.11 */
   mrb_define_method(mrb, bob, "instance_eval",           mrb_obj_instance_eval,    MRB_ARGS_OPT(1)|MRB_ARGS_BLOCK());  /* 15.3.1.3.18 */
+  mrb_define_method(mrb, bob, "singleton_method_added",  mrb_bob_init,             MRB_ARGS_REQ(1));
 
   mrb_define_class_method(mrb, cls, "new",               mrb_class_new_class,      MRB_ARGS_OPT(1)|MRB_ARGS_BLOCK());
   mrb_define_method(mrb, cls, "allocate",                mrb_instance_alloc,       MRB_ARGS_NONE());
@@ -2932,6 +2950,7 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_method(mrb, mod, "define_method",           mod_define_method,        MRB_ARGS_ARG(1,1));
   mrb_define_method(mrb, mod, "===",                     mrb_mod_eqq,              MRB_ARGS_REQ(1)); /* 15.2.2.4.7 */
   mrb_define_method(mrb, mod, "dup",                     mrb_mod_dup,              MRB_ARGS_NONE());
+  mrb_define_method(mrb, bob, "method_added",            mrb_bob_init,             MRB_ARGS_REQ(1));
 
   mrb_undef_method(mrb, cls, "append_features");
   mrb_undef_method(mrb, cls, "prepend_features");
diff --git a/src/vm.c b/src/vm.c
index 560887f00..f76ce9eac 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -1135,6 +1135,7 @@ get_send_args(mrb_state *mrb, mrb_int argc, mrb_value *regs)
 
 mrb_value mrb_obj_missing(mrb_state *mrb, mrb_value mod);
 void mrb_hash_check_kdict(mrb_state *mrb, mrb_value self);
+void mrb_method_added(mrb_state *mrb, struct RClass *c, mrb_sym mid);
 
 MRB_API mrb_value
 mrb_vm_exec(mrb_state *mrb, const struct RProc *proc, const mrb_code *pc)
@@ -2893,9 +2894,11 @@ RETRY_TRY_BLOCK:
       struct RClass *target = mrb_class_ptr(regs[a]);
       struct RProc *p = mrb_proc_ptr(regs[a+1]);
       mrb_method_t m;
+      mrb_sym mid = syms[b];
 
       MRB_METHOD_FROM_PROC(m, p);
-      mrb_define_method_raw(mrb, target, syms[b], m);
+      mrb_define_method_raw(mrb, target, mid, m);
+      mrb_method_added(mrb, target, mid);
       mrb_gc_arena_restore(mrb, ai);
       NEXT;
     }
diff --git a/test/t/methods.rb b/test/t/methods.rb
index f9c25dc33..9005d7976 100644
--- a/test/t/methods.rb
+++ b/test/t/methods.rb
@@ -107,3 +107,32 @@ assert('The undef statement (method undefined)', '13.3.7 a) 5)') do
     undef :non_existing_method
   end
 end
+
+assert('method_added hook') do
+  c = Class.new do
+    # method to retrieve @name
+    def self.name; @name; end
+    # hook method on method definition
+    def self.method_added(name) @name = name; end
+    # method definition
+    def foo; end
+  end
+  assert_equal(:foo, c.name)
+  c.define_method(:bar){}
+  assert_equal(:bar, c.name)
+end
+
+assert('singleton_method_added hook') do
+  a = Object.new
+  # method to retrieve @name
+  def a.name; @name; end
+  # hook method on singleton method definition
+  def a.singleton_method_added(name) @name = name; end
+  # singleton method definition
+  def a.foo; end
+  assert_equal(:foo, a.name)
+  class <<a
+    def bar; end
+  end
+  assert_equal(:bar, a.name)
+end