Merge pull request #914 from fadushin/loggger_manager-fix

Allow use of logging macros without instantiating the logger manager

This change set allows users to use logging macros and functions in code, but
for those calls not to fail with an error if the logger manager has not been
instantiated.

Users must still instantiate the logger manager (or it is instantiated
automatically as part of the kernel application, TBD) in order for logs to pass
the initial allow phase, but all logs will be silently dropped until the EAVMLib
logger manager is instaniated.

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

libs/eavmlib/src/logger_manager.erl

@@ -80,7 +80,17 @@ get_id() ->
 
 %% @hidden
 allow(Level, Module) ->
-    gen_server:call(?MODULE, {allow, Level, Module}).
+    %% if the logger manager has not been instantiated, then
+    %% "fail" silently (i.e., log nothing).  The logger manager
+    %% either needs to be instantiated manually, or it is be done
+    %% so automatically in OTP-style deployment when the kernel
+    %% is started by init.
+    case erlang:whereis(?MODULE) of
+        undefined ->
+            false;
+        _ ->
+            gen_server:call(?MODULE, {allow, Level, Module})
+    end.
 
 %%
 %% gen_server callbacks

tests/libs/estdlib/test_logger.erl

@@ -46,7 +46,11 @@ test_logger() ->
     ok.
 
 test_default_logger() ->
-    ?ASSERT_FAILURE(?LOG_NOTICE("Tried to log before starting log_manager!")),
+    %% silent "failure" (nothing will be logged) if the
+    %% logger manager has not been instantiated.  In OTP-style
+    %% deployment, the logger manager is initialized in
+    %% the kernel application.
+    ok = ?LOG_NOTICE("Tried to log before starting log_manager!"),
 
     {ok, _Pid} = logger_manager:start_link(#{}),