Merge branch 'tp/supervisor-pass-on-errors'

* tp/supervisor-pass-on-errors:
  If supervisor:start_link fails to start child, add child id to error reason
  Fix documentation about how supervisor handles crash in child's start function
  Have supervisor send errors up the chain

OTP-10490

1 files changed, 15 insertions, 10 deletions

diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index 7d3c5a0e21..9f93747c3e 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -104,7 +104,9 @@
 %%% SupName = {local, atom()} | {global, atom()}.
 %%% ---------------------------------------------------
 
--type startlink_err() :: {'already_started', pid()} | 'shutdown' | term().
+-type startlink_err() :: {'already_started', pid()}
+                         | {'shutdown', term()}
+                         | term().
 -type startlink_ret() :: {'ok', pid()} | 'ignore' | {'error', startlink_err()}.
 
 -spec start_link(Module, Args) -> startlink_ret() when
@@ -221,8 +223,10 @@ cast(Supervisor, Req) ->
 
 -type init_sup_name() :: sup_name() | 'self'.
 
--type stop_rsn() :: 'shutdown' | {'bad_return', {module(),'init', term()}}
-                  | {'bad_start_spec', term()} | {'start_spec', term()}
+-type stop_rsn() :: {'shutdown', term()}
+                  | {'bad_return', {module(),'init', term()}}
+                  | {'bad_start_spec', term()}
+                  | {'start_spec', term()}
                   | {'supervisor_data', term()}.
 
 -spec init({init_sup_name(), module(), [term()]}) ->
@@ -253,9 +257,9 @@ init_children(State, StartSpec) ->
             case start_children(Children, SupName) of
                 {ok, NChildren} ->
                     {ok, State#state{children = NChildren}};
-                {error, NChildren} ->
+                {error, NChildren, Reason} ->
                     terminate_children(NChildren, SupName),
-                    {stop, shutdown}
+                    {stop, {shutdown, Reason}}
             end;
         Error ->
             {stop, {start_spec, Error}}
@@ -275,9 +279,9 @@ init_dynamic(_State, StartSpec) ->
 %% Func: start_children/2
 %% Args: Children = [child_rec()] in start order
 %%       SupName = {local, atom()} | {global, atom()} | {pid(), Mod}
-%% Purpose: Start all children.  The new list contains #child's 
+%% Purpose: Start all children.  The new list contains #child's
 %%          with pids.
-%% Returns: {ok, NChildren} | {error, NChildren}
+%% Returns: {ok, NChildren} | {error, NChildren, Reason}
 %%          NChildren = [child_rec()] in termination order (reversed
 %%                        start order)
 %%-----------------------------------------------------------------
@@ -293,7 +297,8 @@ start_children([Child|Chs], NChildren, SupName) ->
 	    start_children(Chs, [Child#child{pid = Pid}|NChildren], SupName);
 	{error, Reason} ->
 	    report_error(start_error, Reason, Child, SupName),
-	    {error, lists:reverse(Chs) ++ [Child | NChildren]}
+	    {error, lists:reverse(Chs) ++ [Child | NChildren],
+	     {failed_to_start_child,Child#child.name,Reason}}
     end;
 start_children([], NChildren, _SupName) ->
     {ok, NChildren}.
@@ -793,7 +798,7 @@ restart(rest_for_one, Child, State) ->
     case start_children(ChAfter2, State#state.name) of
 	{ok, ChAfter3} ->
 	    {ok, State#state{children = ChAfter3 ++ ChBefore}};
-	{error, ChAfter3} ->
+	{error, ChAfter3, _Reason} ->
 	    NChild = Child#child{pid=restarting(Child#child.pid)},
 	    NState = State#state{children = ChAfter3 ++ ChBefore},
 	    {try_again, replace_child(NChild,NState)}
@@ -804,7 +809,7 @@ restart(one_for_all, Child, State) ->
     case start_children(Children2, State#state.name) of
 	{ok, NChs} ->
 	    {ok, State#state{children = NChs}};
-	{error, NChs} ->
+	{error, NChs, _Reason} ->
 	    NChild = Child#child{pid=restarting(Child#child.pid)},
 	    NState = State#state{children = NChs},
 	    {try_again, replace_child(NChild,NState)}