ct: Introduce replace mode to cth_log_redirect

In addition to the existing way of logging to both the CT HTML logs and
console, allow users to completely replace the standard logging handler
with the log redirect hook, effectively silencing console logging
output during Common Test runs.

Mostly taken from erlang#7375, with the caveat that "add" mode continues being
the default, and no changes outside of the hook take place.

Additionally, group cth_log_redirect test cases together to allow for
easier module verification.

Author: jchristgit

lib/common_test/doc/src/ct_hooks_chapter.xml

@@ -511,6 +511,25 @@ results(State) ->
         use another level either change the <c>default</c> handler level before
         starting common_test, or use the <seemfa marker="kernel:logger#set_handler_config/3">
         <c>logger:set_handler_config/3</c></seemfa> API.</p>
+        <p>This hook supports the following options:</p>
+        <taglist>
+          <tag><c>{mode, add}</c></tag>
+          <item>
+            <p>Add <c>cth_log_redirect</c> to the default logging handler:
+              Logs will be emitted to both standard output via the
+              default handler, and into the Common Test HTML logs.
+              This is the default behaviour.</p>
+          </item>
+          <tag><c>{mode, replace}</c></tag>
+          <item>
+            <p>Replace the <c>default</c> logging handler with <c>cth_log_redirect</c>
+              instead of logging to both the default handler and this handler.
+              This effectively silences any logger output which would normally be printed
+              to standard output during test runs. To enable this mode, you can pass
+              the following options to <c>ct_run</c>:</p>
+            <p><c>-enable_builtin_hooks false -ct_hooks cth_log_redirect [{mode,replace}]</c></p>
+          </item>
+        </taglist>
        </item>
        <tag><c>cth_surefire</c></tag>
        <item>

lib/common_test/src/cth_log_redirect.erl

@@ -21,7 +21,8 @@
 
 %%% Common Test Framework functions handling test specifications.
 %%%
-%%% This module redirects sasl and error logger info to common test log.
+%%% This module redirects sasl, error logger, and standard logger messages to
+%%% the common test log.
 
 %% CTH Callbacks
 -export([id/1, init/2,
@@ -56,9 +57,9 @@
 id(_Opts) ->
     ?MODULE.
 
-init(?MODULE, _Opts) ->
+init(?MODULE, Opts) ->
     ct_util:mark_process(),
-    ok = start_log_handler(),
+    ok = start_log_handler(Opts),
     {ok, tc_log_async}.
 
 pre_init_per_suite(Suite, Config, State) ->
@@ -115,7 +116,7 @@ post_end_per_group(_Suite, _Group, Config, Return, State) ->
     set_curr_func({group,undefined}, Config),
     {Return, State}.
 
-start_log_handler() ->
+start_log_handler(Options) ->
     case whereis(?MODULE) of
         undefined ->
             ChildSpec =
@@ -137,9 +138,15 @@ start_log_handler() ->
             _Else ->
                 {{?DEFAULT_FORMATTER,?DEFAULT_FORMAT_CONFIG},info}
         end,
-    ok = logger:add_handler(?MODULE,?MODULE,
-                            #{level=>DefaultLevel,
-                              formatter=>DefaultFormatter}).
+    HandlerConfig = #{level => DefaultLevel, formatter => DefaultFormatter},
+    HandlerName = case proplists:get_value(mode, Options, add) of
+                      add ->
+                          ?MODULE;
+                      replace ->
+                          ok = logger:remove_handler(default),
+                          default
+                  end,
+    ok = logger:add_handler(HandlerName, ?MODULE, HandlerConfig).
 
 init([]) ->
     {ok, #eh_state{log_func = tc_log_async}}.

lib/common_test/test/ct_hooks_SUITE.erl

@@ -112,10 +112,16 @@ all(suite) ->
        no_init_suite_config, no_init_config, no_end_config,
        failed_sequence, repeat_force_stop, config_clash,
        callbacks_on_skip, fallback, data_dir,
-       cth_log, cth_log_formatter, cth_log_unexpect
+       {group, cth_log_redirect}
       ]
     ).
 
+groups() ->
+    [
+     {cth_log_redirect, [], [cth_log_unexpect, cth_log_formatter,
+                             cth_log, cth_log_mode_replace]}
+    ].
+
 
 %%--------------------------------------------------------------------
 %% TEST CASES
@@ -300,36 +306,7 @@ data_dir(Config) when is_list(Config) ->
 cth_log(Config) when is_list(Config) ->
     %% test that cth_log_redirect writes properly to
     %% html I/O log
-    ct:timetrap({minutes,10}),
-    StartOpts = do_test(cth_log, "cth_log_SUITE.erl", [], Config),
-    Logdir = proplists:get_value(logdir, StartOpts),
-    TCLogs =
-	filelib:wildcard(
-	  filename:join(Logdir,
-			"ct_run*/cth.tests*/run*/cth_log_suite.tc*.html")),
-    lists:foreach(
-      fun(TCLog) ->
-	      {ok,Bin} = file:read_file(TCLog),
-	      Ts = string:lexemes(binary_to_list(Bin),[$\n]),
-	      Matches = lists:foldl(fun("=ERROR"++_,  {E,I,N,L}) ->
-					    {E+1,I,N,L};
-				       ("=INFO"++_,  {E,I,N,L}) ->
-					    {E,I+1,N,L};
-				       ("=NOTICE"++_,  {E,I,N,L}) ->
-					    {E,I,N+1,L};
-				       ("Logger"++_,  {E,I,N,L}) ->
-					    {E,I,N,L+1};
-				       (_, N) -> N
-				    end, {0,0,0,0}, Ts),
-	      ct:pal("~p ({Error,Info,Notice,Log}) matches in ~tp",
-                     [Matches,TCLog]),
-              MatchList = tuple_to_list(Matches),
-              case [N || N <- MatchList, N<1] of
-                  [] -> ok;
-                  _ -> exit({missing_io,TCLog})
-	      end
-      end, TCLogs),
-    ok.
+    verify_cth_log_output(Config, [], []).
 
 cth_log_formatter(Config) when is_list(Config) ->
     %% test that cth_log_redirect writes properly to
@@ -398,6 +375,12 @@ cth_log_unexpect(Config) when is_list(Config) ->
       end, UnexpIoLogs),
     ok.
 
+cth_log_mode_replace(Config) when is_list(Config) ->
+    %% test that cth_log_redirect writes properly to
+    %% html I/O log when replace mode is used
+    verify_cth_log_output(Config, [{cth_log_redirect, [{mode, replace}]}],
+                          [{enable_builtin_hooks, false}]).
+
 %% OTP-10599 adds the Suite argument as first argument to all hook
 %% callbacks that did not have a Suite argument from before. This test
 %% checks that ct_hooks will fall back to old versions of callbacks if
@@ -542,6 +525,39 @@ gen_config(Name,KeyVals,Config) ->
                                || {Key,Value} <- KeyVals]),
     File.
 
+verify_cth_log_output(Config, CTHooks, ExtraOpts) ->
+    ct:timetrap({minutes,10}),
+    StartOpts = do_test(cth_log, "cth_log_SUITE.erl", CTHooks, Config, ok, 2, ExtraOpts),
+    Logdir = proplists:get_value(logdir, StartOpts),
+    TCLogs =
+	filelib:wildcard(
+	  filename:join(Logdir,
+			"ct_run*/cth.tests*/run*/cth_log_suite.tc*.html")),
+    lists:foreach(
+      fun(TCLog) ->
+	      {ok,Bin} = file:read_file(TCLog),
+	      Ts = string:lexemes(binary_to_list(Bin),[$\n]),
+	      Matches = lists:foldl(fun("=ERROR"++_,  {E,I,N,L}) ->
+					    {E+1,I,N,L};
+				       ("=INFO"++_,  {E,I,N,L}) ->
+					    {E,I+1,N,L};
+				       ("=NOTICE"++_,  {E,I,N,L}) ->
+					    {E,I,N+1,L};
+				       ("Logger"++_,  {E,I,N,L}) ->
+					    {E,I,N,L+1};
+				       (_, N) -> N
+				    end, {0,0,0,0}, Ts),
+	      ct:pal("~p ({Error,Info,Notice,Log}) matches in ~tp",
+                     [Matches,TCLog]),
+              MatchList = tuple_to_list(Matches),
+              case [N || N <- MatchList, N<1] of
+                  [] -> ok;
+                  _ -> exit({missing_io,TCLog})
+	      end
+      end, TCLogs),
+    ok.
+
+
 %%%-----------------------------------------------------------------
 %%% TEST EVENTS
 %%%-----------------------------------------------------------------