add verbosity config option, output only errors unless set

config/test.pass.config

@@ -0,0 +1,15 @@
+[ % this check passes
+ {
+   elvis,
+   [
+    {config,
+     [#{dirs => ["../../_build/test/lib/elvis/test/examples"],
+        filter => "**.erl",
+        rules => [{elvis_style, line_length, #{limit => 800}]
+       }]
+    },
+    {output_format, plain}
+   ]
+ }
+].
+

src/elvis_result.erl

@@ -1,5 +1,7 @@
 -module(elvis_result).
 
+-compile({no_auto_import, [error/2]}).
+
 %% API
 -export([
          new/3,
@@ -112,22 +114,22 @@ print([Result | Results]) ->
 %% File
 print(#{file := File, rules := Rules}) ->
     Path = elvis_file:path(File),
-    Status = case status(Rules) of
-                 ok -> "{{green-bold}}OK";
-                 fail -> "{{red-bold}}FAIL"
-             end,
-
-    elvis_utils:notice("# ~s [~s{{white-bold}}]", [Path, Status]),
+    case status(Rules) of
+        ok ->
+          elvis_utils:notice("# ~s [{{green-bold}}OK{{white-bold}}]", [Path]);
+        fail ->
+          elvis_utils:error("# ~s [{{red-bold}}FAIL{{white-bold}}]", [Path])
+    end,
     print(Rules);
 %% Rule
 print(#{items := []}) ->
     ok;
 print(#{name := Name, items := Items}) ->
-    elvis_utils:notice("  - ~s", [atom_to_list(Name)]),
+    elvis_utils:error("  - ~s", [atom_to_list(Name)]),
     print(Items);
 %% Item
 print(#{message := Msg, info := Info}) ->
-    elvis_utils:notice("    - " ++ Msg, Info);
+    elvis_utils:error("    - " ++ Msg, Info);
 %% Error
 print(#{error_msg := Msg, info := Info}) ->
     elvis_utils:error_prn(Msg, Info).

src/elvis_utils.erl

@@ -1,5 +1,7 @@
 -module(elvis_utils).
 
+-compile({no_auto_import, [error/2]}).
+
 -export([
          %% Rules
          check_lines/3,
@@ -16,6 +18,8 @@
          info/2,
          notice/1,
          notice/2,
+         error/1,
+         error/2,
          error_prn/1,
          error_prn/2,
          parse_colors/1
@@ -129,7 +133,7 @@ info(Message) ->
 -spec info(string(), [term()]) -> ok.
 info(Message, Args) ->
     ColoredMessage = Message ++ "{{reset}}~n",
-    print(ColoredMessage, Args).
+    print_info(ColoredMessage, Args).
 
 -spec notice(string()) -> ok.
 notice(Message) ->
@@ -138,8 +142,16 @@ notice(Message) ->
 -spec notice(string(), [term()]) -> ok.
 notice(Message, Args) ->
     ColoredMessage = "{{white-bold}}" ++ Message ++ "{{reset}}~n",
-    print(ColoredMessage, Args).
+    print_info(ColoredMessage, Args).
+
+-spec error(string()) -> ok.
+error(Message) ->
+    error(Message, []).
 
+-spec error(string(), [term()]) -> ok.
+error(Message, Args) ->
+    ColoredMessage = "{{white-bold}}" ++ Message ++ "{{reset}}~n",
+    print(ColoredMessage, Args).
 
 -spec error_prn(string()) -> ok.
 error_prn(Message) ->
@@ -150,6 +162,13 @@ error_prn(Message, Args) ->
     ColoredMessage = "{{red}}Error: {{reset}}" ++ Message ++ "{{reset}}~n",
     print(ColoredMessage, Args).
 
+-spec print_info(string(), [term()]) -> ok.
+print_info(Message, Args) ->
+    case application:get_env(elvis, verbose) of
+        {ok, true} -> print(Message, Args);
+        _ -> ok
+    end.
+
 -spec print(string(), [term()]) -> ok.
 print(Message, Args) ->
     case application:get_env(elvis, no_output) of

test/elvis_SUITE.erl

@@ -19,8 +19,12 @@
          rock_this_not_skipping_files/1,
          rock_this_skipping_files/1,
          rock_without_colors/1,
+         rock_with_no_output_has_no_output/1,
+         rock_with_errors_has_output/1,
+         rock_without_errors_has_no_output/1,
+         rock_without_errors_and_with_verbose_has_output/1,
          rock_with_rule_groups/1,
-         %% Utill & Config
+         %% Util & Config
          throw_configuration/1,
          find_file_and_check_src/1,
          find_file_with_ignore/1,
@@ -185,6 +189,44 @@ rock_without_colors(_Config) ->
              _:{badmatch, []} -> ok
          end.
 
+-spec rock_with_no_output_has_no_output(config()) -> ok.
+rock_with_no_output_has_no_output(_Config) ->
+    application:set_env(elvis, no_output, true),
+    ConfigPath = "../../config/test.config",
+    ElvisConfig = elvis_config:load_file(ConfigPath),
+    Fun = fun() -> elvis_core:rock(ElvisConfig) end,
+    [] = check_no_line_output(Fun),
+    application:unset_env(elvis, no_output),
+    ok.
+
+-spec rock_with_errors_has_output(config()) -> ok.
+rock_with_errors_has_output(_Config) ->
+    ConfigPath = "../../config/test.config",
+    ElvisConfig = elvis_config:load_file(ConfigPath),
+    Fun = fun() -> elvis_core:rock(ElvisConfig) end,
+    Expected = "FAIL",
+    [_|_] = check_some_line_output(Fun, Expected, fun matches_regex/2),
+    ok.
+
+-spec rock_without_errors_has_no_output(config()) -> ok.
+rock_without_errors_has_no_output(_Config) ->
+    ConfigPath = "../../config/test.pass.config",
+    ElvisConfig = elvis_config:load_file(ConfigPath),
+    Fun = fun() -> elvis_core:rock(ElvisConfig) end,
+    [] = check_no_line_output(Fun),
+    ok.
+
+-spec rock_without_errors_and_with_verbose_has_output(config()) -> ok.
+rock_without_errors_and_with_verbose_has_output(_Config) ->
+    application:set_env(elvis, verbose, true),
+    ConfigPath = "../../config/test.pass.config",
+    ElvisConfig = elvis_config:load_file(ConfigPath),
+    Fun = fun() -> elvis_core:rock(ElvisConfig) end,
+    Expected = "OK",
+    [_|_] = check_some_line_output(Fun, Expected, fun matches_regex/2),
+    application:unset_env(elvis, verbose),
+    ok.
+
 -spec rock_with_rule_groups(Config::config()) -> ok.
 rock_with_rule_groups(_Config) ->
     % elvis_config will load default elvis_core rules for every
@@ -315,6 +357,12 @@ check_some_line_output(Fun, Expected, FilterFun) ->
     ListFun = fun(Line) -> FilterFun(Line, Expected) end,
     [_ | _] = lists:filter(ListFun, Lines).
 
+check_no_line_output(Fun) ->
+    _ = ct:capture_start(),
+    _ = Fun(),
+    _ = ct:capture_stop(),
+    [] = ct:capture_get([]).
+
 matches_regex(Result, Regex) ->
     case re:run(Result, Regex) of
         {match, _} -> true;