rabbitmq_prelaunch: Fix all warnings reported by Dialyzer

They are all return values being unmatched. Many were related to list
comprehensions being used as a loop mechanism but the result was unused.
These list comprehensions were replaced by lists:foreach/2.

5 files changed, 42 insertions, 25 deletions

diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
index 4091e28b0c..b564fadf51 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
@@ -219,6 +219,7 @@ remove_pid_file(#{pid_file := PidFile, keep_pid_file_on_exit := true}) ->
     ok;
 remove_pid_file(#{pid_file := PidFile}) ->
     rabbit_log_prelaunch:debug("Deleting PID file: ~s", [PidFile]),
-    _ = file:delete(PidFile);
+    _ = file:delete(PidFile),
+    ok;
 remove_pid_file(_) ->
     ok.
diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
index 928cc45e14..0e107a007d 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
@@ -192,8 +192,11 @@ generate_config_from_cuttlefish_files(Context,
         _ ->
             rabbit_log_prelaunch:debug(
               "Configuration schemas found:~n", []),
-            [rabbit_log_prelaunch:debug("  - ~ts", [SchemaFile])
-             || SchemaFile <- SchemaFiles],
+            lists:foreach(
+              fun(SchemaFile) ->
+                      rabbit_log_prelaunch:debug("  - ~ts", [SchemaFile])
+              end,
+              SchemaFiles),
             ok
     end,
     Schema = cuttlefish_schema:files(SchemaFiles),
@@ -201,15 +204,17 @@ generate_config_from_cuttlefish_files(Context,
     %% Load configuration.
     rabbit_log_prelaunch:debug(
       "Loading configuration files (Cuttlefish based):"),
-    [rabbit_log_prelaunch:debug(
-       "  - ~ts", [ConfigFile]) || ConfigFile <- ConfigFiles],
+    lists:foreach(
+      fun(ConfigFile) ->
+              rabbit_log_prelaunch:debug("  - ~ts", [ConfigFile])
+      end, ConfigFiles),
     case cuttlefish_conf:files(ConfigFiles) of
         {errorlist, Errors} ->
             rabbit_log_prelaunch:error("Error generating configuration:", []),
-            [rabbit_log_prelaunch:error(
-               "  - ~ts",
-               [cuttlefish_error:xlate(Error)])
-             || Error <- Errors],
+            lists:foreach(
+              fun(Error) ->
+                      rabbit_log_prelaunch:error("  - ~ts", [cuttlefish_error:xlate(Error)])
+              end, Errors),
             throw({error, failed_to_generate_configuration_file});
         Config0 ->
             %% Finalize configuration, based on the schema.
@@ -219,10 +224,12 @@ generate_config_from_cuttlefish_files(Context,
                              rabbit_log_prelaunch:error(
                                "Error generating configuration in phase ~ts:",
                                [Phase]),
-                             [rabbit_log_prelaunch:error(
-                                "  - ~ts",
-                                [cuttlefish_error:xlate(Error)])
-                              || Error <- Errors],
+                             lists:foreach(
+                               fun(Error) ->
+                                       rabbit_log_prelaunch:error(
+                                         "  - ~ts",
+                                         [cuttlefish_error:xlate(Error)])
+                               end, Errors),
                              throw(
                                {error, failed_to_generate_configuration_file});
                          ValidConfig ->
@@ -294,7 +301,8 @@ list_schemas_in_app(App) ->
                    []
            end,
     case Unload of
-        true  -> application:unload(App);
+        true  -> _ = application:unload(App),
+                 ok;
         false -> ok
     end,
     List.
@@ -447,11 +455,11 @@ get_passphrase(ConfigEntryDecoder) ->
     case proplists:get_value(passphrase, ConfigEntryDecoder) of
         prompt ->
             IoDevice = get_input_iodevice(),
-            io:setopts(IoDevice, [{echo, false}]),
+            ok = io:setopts(IoDevice, [{echo, false}]),
             PP = lists:droplast(io:get_line(IoDevice,
                 "\nPlease enter the passphrase to unlock encrypted "
                 "configuration entries.\n\nPassphrase: ")),
-            io:setopts(IoDevice, [{echo, true}]),
+            ok = io:setopts(IoDevice, [{echo, true}]),
             io:format(IoDevice, "~n", []),
             PP;
         {file, Filename} ->
diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_dist.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_dist.erl
index ccb3c28ab6..3d718438a7 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_dist.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_dist.erl
@@ -33,9 +33,11 @@ do_setup(#{nodename := Node, nodename_type := NameType}) ->
             %% "minimum transition traffic interval" as defined in
             %% net_kernel:set_net_ticktime/1.
             MTTI = Ticktime * 1000 div 4,
-            {ok, _} = net_kernel:start([Node, NameType, MTTI]);
+            {ok, _} = net_kernel:start([Node, NameType, MTTI]),
+            ok;
         _ ->
-            {ok, _} = net_kernel:start([Node, NameType])
+            {ok, _} = net_kernel:start([Node, NameType]),
+            ok
     end,
     ok.
 
@@ -53,7 +55,7 @@ duplicate_node_check(#{split_nodename := {NodeName, NodeHost}}) ->
                 true ->
                     throw({error, {duplicate_node_name, NodeName, NodeHost}});
                 false ->
-                    net_kernel:stop(),
+                    ok = net_kernel:stop(),
                     ok
             end;
         {error, EpmdReason} ->
diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_early_logging.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_early_logging.erl
index d5a5486f10..431422276f 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_early_logging.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_early_logging.erl
@@ -35,8 +35,9 @@ do_setup_early_logging(#{log_levels := LogLevels} = Context,
                             #{global := Level} -> Level;
                             _                  -> warning
                         end,
-            lager_app:start_handler(
-              lager_event, ConsoleBackend, [{level, GLogLevel}]);
+            _ = lager_app:start_handler(
+                  lager_event, ConsoleBackend, [{level, GLogLevel}]),
+            ok;
         false ->
             ok
     end,
@@ -99,8 +100,10 @@ get_log_level(LogLevels, Sink) ->
 
 enable_quick_dbg(#{dbg_output := Output, dbg_mods := Mods}) ->
     case Output of
-        stdout -> {ok, _} = dbg:tracer();
-        _      -> {ok, _} = dbg:tracer(port, dbg:trace_port(file, Output))
+        stdout -> {ok, _} = dbg:tracer(),
+                  ok;
+        _      -> {ok, _} = dbg:tracer(port, dbg:trace_port(file, Output)),
+                  ok
     end,
     {ok, _} = dbg:p(all, c),
     lists:foreach(fun(M) -> {ok, _} = dbg:tp(M, cx) end, Mods).
diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_errors.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_errors.erl
index 86bf579210..2a2eb2b7fd 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_errors.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_errors.erl
@@ -103,7 +103,10 @@ log_message(Message) ->
               ?BOOT_FAILED_FOOTER,
               [$\n],
               all),
-    [rabbit_log_prelaunch:error("~s", [Line]) || Line <- Lines],
-    [io:format(standard_error, "~s~n", [Line]) || Line <- Lines],
+    lists:foreach(
+      fun(Line) ->
+              rabbit_log_prelaunch:error("~s", [Line]),
+              io:format(standard_error, "~s~n", [Line])
+      end, Lines),
     timer:sleep(1000),
     ok.