Use DEFAULT_SCOPE macro.

src/syn.hrl

@@ -70,10 +70,13 @@
 -record(state, {
     handler = undefined :: undefined | module(),
     handler_state = undefined :: any(),
-    scope = default :: atom(),
+    scope = undefined :: atom(),
     process_name :: atom(),
     nodes_map = #{} :: #{node() => pid()},
     multicast_pid :: pid(),
     table_by_name :: atom(),
     table_by_pid :: atom()
 }).
+
+%% macros
+-define(DEFAULT_SCOPE, default).

src/syn_groups.erl

@@ -64,7 +64,7 @@ get_subcluster_nodes(Scope) ->
 
 -spec members(GroupName :: term()) -> [{Pid :: pid(), Meta :: term()}].
 members(GroupName) ->
-    members(default, GroupName).
+    members(?DEFAULT_SCOPE, GroupName).
 
 -spec members(Scope :: atom(), GroupName :: term()) -> [{Pid :: pid(), Meta :: term()}].
 members(Scope, GroupName) ->
@@ -72,7 +72,7 @@ members(Scope, GroupName) ->
 
 -spec is_member(GroupName :: any(), Pid :: pid()) -> boolean().
 is_member(GroupName, Pid) ->
-    is_member(default, GroupName, Pid).
+    is_member(?DEFAULT_SCOPE, GroupName, Pid).
 
 -spec is_member(Scope :: atom(), GroupName :: any(), Pid :: pid()) -> boolean().
 is_member(Scope, GroupName, Pid) ->
@@ -89,7 +89,7 @@ is_member(Scope, GroupName, Pid) ->
 
 -spec local_members(GroupName :: term()) -> [{Pid :: pid(), Meta :: term()}].
 local_members(GroupName) ->
-    local_members(default, GroupName).
+    local_members(?DEFAULT_SCOPE, GroupName).
 
 -spec local_members(Scope :: atom(), GroupName :: term()) -> [{Pid :: pid(), Meta :: term()}].
 local_members(Scope, GroupName) ->
@@ -111,7 +111,7 @@ do_get_members(Scope, GroupName, NodeParam) ->
 
 -spec is_local_member(GroupName :: any(), Pid :: pid()) -> boolean().
 is_local_member(GroupName, Pid) ->
-    is_local_member(default, GroupName, Pid).
+    is_local_member(?DEFAULT_SCOPE, GroupName, Pid).
 
 -spec is_local_member(Scope :: atom(), GroupName :: any(), Pid :: pid()) -> boolean().
 is_local_member(Scope, GroupName, Pid) ->
@@ -132,7 +132,7 @@ join(GroupName, Pid) ->
 
 -spec join(GroupNameOrScope :: term(), PidOrGroupName :: term(), MetaOrPid :: term()) -> ok.
 join(GroupName, Pid, Meta) when is_pid(Pid) ->
-    join(default, GroupName, Pid, Meta);
+    join(?DEFAULT_SCOPE, GroupName, Pid, Meta);
 
 join(Scope, GroupName, Pid) when is_pid(Pid) ->
     join(Scope, GroupName, Pid, undefined).
@@ -155,7 +155,7 @@ join(Scope, GroupName, Pid, Meta) ->
 
 -spec leave(GroupName :: any(), Pid :: pid()) -> ok | {error, Reason :: any()}.
 leave(GroupName, Pid) ->
-    leave(default, GroupName, Pid).
+    leave(?DEFAULT_SCOPE, GroupName, Pid).
 
 -spec leave(Scope :: atom(), GroupName :: any(), Pid :: pid()) -> ok | {error, Reason :: any()}.
 leave(Scope, GroupName, Pid) ->

src/syn_registry.erl

@@ -66,7 +66,7 @@ get_subcluster_nodes(Scope) ->
 
 -spec lookup(Name :: term()) -> {pid(), Meta :: term()} | undefined.
 lookup(Name) ->
-    lookup(default, Name).
+    lookup(?DEFAULT_SCOPE, Name).
 
 -spec lookup(Scope :: atom(), Name :: term()) -> {pid(), Meta :: term()} | undefined.
 lookup(Scope, Name) ->
@@ -83,11 +83,11 @@ lookup(Scope, Name) ->
 
 -spec register(Name :: term(), Pid :: pid()) -> ok | {error, Reason :: term()}.
 register(Name, Pid) ->
-    register(default, Name, Pid, undefined).
+    register(?DEFAULT_SCOPE, Name, Pid, undefined).
 
 -spec register(NameOrScope :: term(), PidOrName :: term(), MetaOrPid :: term()) -> ok | {error, Reason :: term()}.
 register(Name, Pid, Meta) when is_pid(Pid) ->
-    register(default, Name, Pid, Meta);
+    register(?DEFAULT_SCOPE, Name, Pid, Meta);
 
 register(Scope, Name, Pid) when is_pid(Pid) ->
     register(Scope, Name, Pid, undefined).
@@ -110,7 +110,7 @@ register(Scope, Name, Pid, Meta) ->
 
 -spec unregister(Name :: term()) -> ok | {error, Reason :: term()}.
 unregister(Name) ->
-    unregister(default, Name).
+    unregister(?DEFAULT_SCOPE, Name).
 
 -spec unregister(Scope :: atom(), Name :: term()) -> ok | {error, Reason :: term()}.
 unregister(Scope, Name) ->

src/syn_sup.erl

@@ -33,6 +33,9 @@
 %% Supervisor callbacks
 -export([init/1]).
 
+%% includes
+-include("syn.hrl").
+
 %% ===================================================================
 %% API
 %% ===================================================================
@@ -44,8 +47,8 @@ start_link() ->
 node_scopes() ->
     %% always have a default scope for all nodes
     case application:get_env(syn, custom_scopes) of
-        undefined -> [default];
-        {ok, Scopes} -> [default] ++ maps:keys(Scopes)
+        undefined -> [?DEFAULT_SCOPE];
+        {ok, Scopes} -> [?DEFAULT_SCOPE] ++ maps:keys(Scopes)
     end.
 
 -spec add_node_to_scope(Scope :: atom()) -> ok.