Merge pull request #1755 from petermm/sup_which_children

Add which_children/1 to supervisor.erl

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

CHANGELOG.md

@@ -52,6 +52,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `erlang:module_loaded/1`
 - Added `binary:replace/3`, `binary:replace/4`
 - Added `binary:match/2` and `binary:match/3`
+- Added `supervisor:which_children/1`
 
 ### Changed
 

libs/estdlib/src/supervisor.erl

@@ -28,7 +28,8 @@
     start_child/2,
     terminate_child/2,
     restart_child/2,
-    delete_child/2
+    delete_child/2,
+    which_children/1
 ]).
 
 -export([
@@ -86,7 +87,8 @@
     start :: {module(), atom(), [any()] | undefined},
     restart :: restart(),
     shutdown :: shutdown(),
-    type :: child_type
+    type :: child_type,
+    modules = [] :: [module()] | dynamic
 }).
 -record(state, {restart_strategy :: strategy(), children = [] :: [#child{}]}).
 
@@ -107,6 +109,9 @@ restart_child(Supervisor, ChildId) ->
 delete_child(Supervisor, ChildId) ->
     gen_server:call(Supervisor, {delete_child, ChildId}).
 
+which_children(Supervisor) ->
+    gen_server:call(Supervisor, which_children).
+
 init({Mod, Args}) ->
     erlang:process_flag(trap_exit, true),
     case Mod:init(Args) of
@@ -123,13 +128,14 @@ init({Mod, Args}) ->
     end.
 
 -spec child_spec_to_record(child_spec()) -> #child{}.
-child_spec_to_record({ChildId, MFA, Restart, Shutdown, Type, _Modules}) ->
+child_spec_to_record({ChildId, MFA, Restart, Shutdown, Type, Modules}) ->
     #child{
         id = ChildId,
         start = MFA,
         restart = Restart,
         shutdown = Shutdown,
-        type = Type
+        type = Type,
+        modules = Modules
     };
 child_spec_to_record(#{id := ChildId, start := MFA} = ChildMap) ->
     Restart = maps:get(restart, ChildMap, permanent),
@@ -142,12 +148,21 @@ child_spec_to_record(#{id := ChildId, start := MFA} = ChildMap) ->
             supervisor -> infinity
         end
     ),
+    Modules = maps:get(
+        modules,
+        ChildMap,
+        case MFA of
+            {M, _, _} -> [M];
+            _ -> []
+        end
+    ),
     #child{
         id = ChildId,
         start = MFA,
         restart = Restart,
         shutdown = Shutdown,
-        type = Type
+        type = Type,
+        modules = Modules
     }.
 
 init_state([ChildSpec | T], State) ->
@@ -262,7 +277,10 @@ handle_call({delete_child, ID}, _From, #state{children = Children} = State) ->
             {reply, {error, running}, State};
         false ->
             {reply, {error, not_found}, State}
-    end.
+    end;
+handle_call(which_children, _From, #state{children = Children} = State) ->
+    ChildrenInfo = lists:map(fun child_to_info/1, Children),
+    {reply, ChildrenInfo, State}.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
@@ -337,6 +355,15 @@ try_start(#child{start = {M, F, Args}} = Record) ->
             {error, {{'EXIT', Error}, Record}}
     end.
 
+child_to_info(#child{id = Id, pid = Pid, type = Type, modules = Modules}) ->
+    Child =
+        case Pid of
+            undefined -> undefined;
+            {restarting, _} -> restarting;
+            _ when is_pid(Pid) -> Pid
+        end,
+    {Id, Child, Type, Modules}.
+
 do_terminate(#child{pid = Pid, shutdown = brutal_kill}) ->
     exit(Pid, kill);
 do_terminate(#child{pid = Pid, shutdown = infinity}) ->

tests/libs/estdlib/test_supervisor.erl

@@ -33,6 +33,7 @@ test() ->
     ok = test_supervisor_order(),
     ok = test_terminate_delete_child(),
     ok = test_terminate_timeout(),
+    ok = test_which_children(),
     ok.
 
 test_basic_supervisor() ->
@@ -259,3 +260,33 @@ test_supervisor_order() ->
     unlink(SupPid),
     exit(SupPid, shutdown),
     ok.
+
+test_which_children() ->
+    % Test with no children
+    {ok, SupPid} = supervisor:start_link(?MODULE, {test_no_child, self()}),
+    [] = supervisor:which_children(SupPid),
+
+    % Add a child and test
+    {ok, _ChildPid} = supervisor:start_child(SupPid, #{
+        id => test_child,
+        start => {ping_pong_server, start_link, [self()]},
+        restart => permanent,
+        shutdown => 5000,
+        type => worker
+    }),
+
+    % Check which_children returns the child info
+    [{test_child, ChildPid, worker, [ping_pong_server]}] = supervisor:which_children(SupPid),
+    true = is_pid(ChildPid),
+
+    % Terminate the child and check it shows as undefined
+    ok = supervisor:terminate_child(SupPid, test_child),
+    [{test_child, undefined, worker, [ping_pong_server]}] = supervisor:which_children(SupPid),
+
+    % Delete the child and check empty list
+    ok = supervisor:delete_child(SupPid, test_child),
+    [] = supervisor:which_children(SupPid),
+
+    unlink(SupPid),
+    exit(SupPid, shutdown),
+    ok.