global: Allow "tuple funs" as resolve functions

Commit de7e01c958ff7c9e6da4034a53567a30a4ae5792 removed support for
tuple funs. To still allow resolve functions for
global:{re_}register_name/3 to be specified as {M,F}, we'll need to
translate {M,F} to an external fun.

Also update the documentation to mention that the use of {M,F} to
specify a resolve function is deprecated, and to add a recommendation
to use an external fun.

2 files changed, 21 insertions, 3 deletions

diff --git a/lib/kernel/doc/src/global.xml b/lib/kernel/doc/src/global.xml
index 304a9b1d88..9c50049503 100644
--- a/lib/kernel/doc/src/global.xml
+++ b/lib/kernel/doc/src/global.xml
@@ -163,7 +163,8 @@
       <fsummary>Globally register a name for a pid</fsummary>
       <type name="method"/>
       <type_desc name="method">{<c>Module</c>, <c>Function</c>}
-        is also allowed
+        is currently also allowed for backward compatibility, but its use is
+	deprecated
       </type_desc>
       <desc>
         <p>Globally associates the name <c><anno>Name</anno></c> with a pid, that is,
@@ -180,6 +181,15 @@
           unregistered. This function is called once for each name
           clash.</p>
 
+	<warning>
+	  <p>If you plan to change code without restarting your system,
+	  you must use an external fun (<c>fun Module:Function/Arity</c>)
+	  as the <c><anno>Resolve</anno></c> function; if you use a
+	  local fun you can never replace the code for the module that
+	  the fun belongs to.
+	  </p>
+	</warning>
+
         <p>There are three pre-defined resolve functions:
           <c>random_exit_name/3</c>, <c>random_notify_name/3</c>, and
           <c>notify_all_name/3</c>. If no <c><anno>Resolve</anno></c> function is
diff --git a/lib/kernel/src/global.erl b/lib/kernel/src/global.erl
index 36cb713ee1..b24a9d5eac 100644
--- a/lib/kernel/src/global.erl
+++ b/lib/kernel/src/global.erl
@@ -232,7 +232,8 @@ register_name(Name, Pid) when is_pid(Pid) ->
       Name :: term(),
       Pid :: pid(),
       Resolve :: method().
-register_name(Name, Pid, Method) when is_pid(Pid) ->
+register_name(Name, Pid, Method0) when is_pid(Pid) ->
+    Method = allow_tuple_fun(Method0),
     Fun = fun(Nodes) ->
         case (where(Name) =:= undefined) andalso check_dupname(Name, Pid) of
             true ->
@@ -290,7 +291,8 @@ re_register_name(Name, Pid) when is_pid(Pid) ->
       Name :: term(),
       Pid :: pid(),
       Resolve :: method().
-re_register_name(Name, Pid, Method) when is_pid(Pid) ->
+re_register_name(Name, Pid, Method0) when is_pid(Pid) ->
+    Method = allow_tuple_fun(Method0),
     Fun = fun(Nodes) ->
 		  gen_server:multi_call(Nodes,
 					global_name_server,
@@ -2218,3 +2220,9 @@ intersection(_, []) ->
     [];
 intersection(L1, L2) ->
     L1 -- (L1 -- L2).
+
+%% Support legacy tuple funs as resolve functions.
+allow_tuple_fun({M, F}) when is_atom(M), is_atom(F) ->
+    fun M:F/3;
+allow_tuple_fun(Fun) when is_function(Fun, 3) ->
+    Fun.