From ad25bf83114a433b3a63ecc8c0fabeb27417edf9 Mon Sep 17 00:00:00 2001
From: Andrew Thompson <andrew@hijacked.us>
Date: Sat, 2 Feb 2019 17:06:09 -0800
Subject: [PATCH] Add an env var to stop lager actually booting

---
 src/lager_app.erl | 15 ++++++++++-----
 src/lager_sup.erl | 41 +++++++++++++++++++++++------------------
 2 files changed, 33 insertions(+), 23 deletions(-)

diff --git a/src/lager_app.erl b/src/lager_app.erl
index 1475f80..53f880d 100644
--- a/src/lager_app.erl
+++ b/src/lager_app.erl
@@ -226,11 +226,16 @@ get_env(Application, Key, Default) ->
 
 start(_StartType, _StartArgs) ->
     {ok, Pid} = lager_sup:start_link(),
-    SavedHandlers = boot(),
-    _ = boot('__all_extra'),
-    _ = boot('__traces'),
-    clean_up_config_checks(),
-    {ok, Pid, SavedHandlers}.
+    case application:get_env(lager, lager_use_logger, false) of
+        false ->
+            SavedHandlers = boot(),
+            _ = boot('__all_extra'),
+            _ = boot('__traces'),
+            clean_up_config_checks(),
+            {ok, Pid, SavedHandlers};
+        true ->
+            {ok, Pid}
+    end.
 
 boot() ->
     %% Handle the default sink.
diff --git a/src/lager_sup.erl b/src/lager_sup.erl
index 97bfd00..890f272 100644
--- a/src/lager_sup.erl
+++ b/src/lager_sup.erl
@@ -32,24 +32,29 @@ start_link() ->
     supervisor:start_link({local, ?MODULE}, ?MODULE, []).
 
 init([]) ->
-    %% set up the config, is safe even during relups
-    lager_config:new(),
-    %% TODO:
-    %% Always start lager_event as the default and make sure that
-    %% other gen_event stuff can start up as needed
-    %%
-    %% Maybe a new API to handle the sink and its policy?
-    Children = [
-        {lager, {gen_event, start_link, [{local, lager_event}]},
-            permanent, 5000, worker, dynamic},
-        {lager_handler_watcher_sup, {lager_handler_watcher_sup, start_link, []},
-            permanent, 5000, supervisor, [lager_handler_watcher_sup]}],
-
-    CrashLog = decide_crash_log(application:get_env(lager, crash_log, false)),
-
-    {ok, {{one_for_one, 10, 60},
-          Children ++ CrashLog
-         }}.
+    case application:get_env(lager, lager_use_logger, false) of
+        true ->
+            {ok, {{one_for_one, 10, 60}, []}};
+        false ->
+            %% set up the config, is safe even during relups
+            lager_config:new(),
+            %% TODO:
+            %% Always start lager_event as the default and make sure that
+            %% other gen_event stuff can start up as needed
+            %%
+            %% Maybe a new API to handle the sink and its policy?
+            Children = [
+                        {lager, {gen_event, start_link, [{local, lager_event}]},
+                         permanent, 5000, worker, dynamic},
+                        {lager_handler_watcher_sup, {lager_handler_watcher_sup, start_link, []},
+                         permanent, 5000, supervisor, [lager_handler_watcher_sup]}],
+
+            CrashLog = decide_crash_log(application:get_env(lager, crash_log, false)),
+
+            {ok, {{one_for_one, 10, 60},
+                  Children ++ CrashLog
+                 }}
+    end.
 
 validate_positive({ok, Val}, _Default) when is_integer(Val) andalso Val >= 0 ->
     Val;