inaka · bormilan · May 29, 2025 · Apr 14, 2025
diff --git a/doc_rules/elvis_style/no_single_match_maybe.md b/doc_rules/elvis_style/no_single_match_maybe.md
@@ -2,6 +2,9 @@
 
 Single-match maybe statements should be avoided.
 
+> [!NOTE]  
+> This rule only works under Erlang/OTP 27+.
+
 ## Avoid
 
 ```erlang

diff --git a/rebar.config b/rebar.config
@@ -1,6 +1,13 @@
 %% == Compiler and Profiles ==
 
-{erl_opts, [warn_unused_import, warn_export_vars, warnings_as_errors, verbose, report, debug_info]}.
+{erl_opts, [
+    warn_unused_import,
+    warn_export_vars,
+    warnings_as_errors,
+    verbose,
+    report,
+    debug_info
+]}.
 
 {minimum_otp_vsn, "25"}.
 

diff --git a/src/elvis_config.erl b/src/elvis_config.erl
@@ -1,5 +1,7 @@
 -module(elvis_config).
 
+-feature(maybe_expr, enable).
+
 -export([
     from_rebar/1,
     from_file/1,
@@ -82,28 +84,62 @@ validate(Config) ->
     lists:foreach(fun do_validate/1, Config).
 
 do_validate(RuleGroup) ->
-    case maps:is_key(src_dirs, RuleGroup) orelse maps:is_key(dirs, RuleGroup) of
-        false ->
-            throw({invalid_config, {missing_dirs, RuleGroup}});
-        true ->
-            ok
-    end,
-    case maps:is_key(dirs, RuleGroup) of
-        true ->
-            case maps:is_key(filter, RuleGroup) of
-                false ->
-                    throw({invalid_config, {missing_filter, RuleGroup}});
-                true ->
-                    ok
-            end;
-        false ->
-            ok
-    end,
-    case maps:is_key(rules, RuleGroup) orelse maps:is_key(ruleset, RuleGroup) of
+    maybe
+        ok ?= maybe_missing_dirs(RuleGroup),
+        ok ?= maybe_missing_filter(RuleGroup),
+        ok ?= maybe_missing_rules(RuleGroup),
+        ok ?= maybe_invalid_rules(RuleGroup)
+    else
+        {error, Error} ->
+            throw({invalid_config, Error})
+    end.
+
+maybe_missing_dirs(RuleGroup) ->
+    maybe_boolean_wrapper(
+        not (maps:is_key(dirs, RuleGroup) andalso not maps:is_key(filter, RuleGroup)), missing_dir
+    ).
+
+maybe_missing_filter(RuleGroup) ->
+    maybe_boolean_wrapper(
+        maps:is_key(src_dirs, RuleGroup) orelse maps:is_key(dirs, RuleGroup), missing_filter
+    ).
+
+maybe_missing_rules(RuleGroup) ->
+    maybe_boolean_wrapper(
+        maps:is_key(rules, RuleGroup) orelse maps:is_key(ruleset, RuleGroup), missing_rules
+    ).
+
+maybe_boolean_wrapper(true, _Flag) -> ok;
+maybe_boolean_wrapper(false, Flag) -> {error, Flag}.
+
+maybe_invalid_rules(#{rules := Rules}) ->
+    case invalid_rules(Rules) of
+        [] -> ok;
+        InvalidRules -> {error, {invalid_rules, InvalidRules}}
+    end;
+maybe_invalid_rules(_) ->
+    ok.
+
+invalid_rules(Rules) ->
+    lists:filtermap(fun is_invalid_rule/1, Rules).
+
+is_invalid_rule({Module, RuleName, _}) ->
+    is_invalid_rule({Module, RuleName});
+is_invalid_rule({Module, RuleName}) ->
+    maybe
+        {file, _} ?= code:is_loaded(Module),
+        ExportedRules = erlang:get_module_info(Module, exports),
+        case lists:keyfind(RuleName, 1, ExportedRules) of
+            false -> {true, {invalid_rule, {Module, RuleName}}};
+            _ -> false
+        end
+    else
         false ->
-            throw({invalid_config, {missing_rules, RuleGroup}});
-        true ->
-            ok
+            elvis_utils:warn_prn(
+                "Invalid module (~p) specified in elvis.config.~n",
+                [Module]
+            ),
+            false
     end.
 
 -spec normalize(configs()) -> configs().

diff --git a/src/elvis_core.erl b/src/elvis_core.erl
@@ -138,6 +138,7 @@ load_file_data(Config, File) ->
 -spec main([]) -> true | no_return().
 main([]) ->
     ok = application:load(elvis_core),
+    {module, _} = code:ensure_loaded(elvis_style),
     R = rock(elvis_config:from_file("elvis.config")),
     R =:= ok orelse halt(1).
 

diff --git a/test/elvis_SUITE.erl b/test/elvis_SUITE.erl
@@ -31,7 +31,8 @@
     invalid_file/1,
     to_string/1,
     chunk_fold/1,
-    erl_files_strict_ruleset/1
+    erl_files_strict_ruleset/1,
+    rock_with_invalid_rules/1
 ]).
 
 -define(EXCLUDED_FUNS, [module_info, all, test, init_per_suite, end_per_suite, chunk_fold_task]).
@@ -424,6 +425,23 @@ rock_with_umbrella_apps(_Config) ->
         elvis_core:rock(ElvisConfig),
     ok.
 
+-spec rock_with_invalid_rules(config()) -> any().
+rock_with_invalid_rules(_Config) ->
+    ConfigPath = "../../test/examples/invalid_rules.elvis.config",
+    ElvisConfig = elvis_config:from_file(ConfigPath),
+    ExpectedErrorMessage =
+        {invalid_rules, [
+            {invalid_rule, {elvis_style, not_existing_rule}},
+            {invalid_rule, {elvis_style, what_is_this_rule}}
+        ]},
+    try
+        ok = elvis_core:rock(ElvisConfig),
+        ct:fail("Elvis should not have rocked with ~p", [ElvisConfig])
+    catch
+        {invalid_config, ExpectedErrorMessage} ->
+            ok
+    end.
+
 %%%%%%%%%%%%%%%
 %%% Utils
 

diff --git a/test/examples/invalid_rules.elvis.config b/test/examples/invalid_rules.elvis.config
@@ -0,0 +1,47 @@
+[
+    {elvis, [
+        {config, [
+            #{
+                dirs => ["src"],
+                filter => "*.erl",
+                rules =>
+                    [
+                        {elvis_style, invalid_dynamic_call, #{ignore => [elvis_core]}},
+                        {elvis_style, dont_repeat_yourself, #{min_complexity => 20}},
+                        {elvis_style, no_debug_call, #{ignore => [elvis_result, elvis_utils]}},
+                        {elvis_style, god_modules, #{ignore => [elvis_style]}},
+                        {elvis_style, no_throw, disable},
+                        {elvis_style, not_existing_rule},
+                        {elvis_style, what_is_this_rule, #{ignore => [elvis_style]}},
+                        {not_existing_module, dont_repeat_yourself},
+                        {not_existing_module, dont_repeat_yourself, #{min_complexity => 20}}
+                    ],
+                ruleset => erl_files
+            },
+            #{
+                dirs => ["_build/default/lib/elvis_core/ebin"],
+                filter => "*.beam",
+                rules =>
+                    [
+                        {elvis_style, invalid_dynamic_call, #{ignore => [elvis_core]}},
+                        {elvis_style, dont_repeat_yourself, #{min_complexity => 20}},
+                        {elvis_style, no_debug_call, #{ignore => [elvis_result, elvis_utils]}},
+                        {elvis_style, atom_naming_convention, #{ignore => [elvis_task]}},
+                        {elvis_style, god_modules, #{ignore => [elvis_style]}},
+                        {elvis_style, no_throw, disable}
+                    ],
+                ruleset => beam_files
+            },
+            #{
+                dirs => ["."],
+                filter => "rebar.config",
+                ruleset => rebar_config
+            },
+            #{
+                dirs => ["."],
+                filter => "elvis.config",
+                ruleset => elvis_config
+            }
+        ]}
+    ]}
+].
diff --git a/test/examples/invalid_rules2.elvis.config b/test/examples/invalid_rules2.elvis.config
@@ -0,0 +1,45 @@
+
+[
+    {elvis, [
+        {config, [
+            #{
+                dirs => ["src"],
+                filter => "*.erl",
+                rules =>
+                    [
+                        {elvis_style, invalid_dynamic_call, #{ignore => [elvis_core]}},
+                        {elvis_style, dont_repeat_yourself, #{min_complexity => 20}},
+                        {elvis_style, no_debug_call, #{ignore => [elvis_result, elvis_utils]}},
+                        {elvis_style, god_modules, #{ignore => [elvis_style]}},
+                        {elvis_style, no_throw, disable}
+                    ],
+                ruleset => erl_files
+            },
+            #{
+                dirs => ["_build/default/lib/elvis_core/ebin"],
+                filter => "*.beam",
+                rules =>
+                    [
+                        {elvis_style, invalid_dynamic_call, #{ignore => [elvis_core]}},
+                        {elvis_style, dont_repeat_yourself, #{min_complexity => 20}},
+                        {elvis_style, no_debug_call, #{ignore => [elvis_result, elvis_utils]}},
+                        {elvis_style, atom_naming_convention, #{ignore => [elvis_task]}},
+                        {elvis_style, god_modules, #{ignore => [elvis_style]}},
+                        {elvis_style, no_throw, disable},
+                        {not_existing_beam_module, no_throw, disable}
+                    ],
+                ruleset => beam_files
+            },
+            #{
+                dirs => ["."],
+                filter => "rebar.config",
+                ruleset => rebar_config
+            },
+            #{
+                dirs => ["."],
+                filter => "elvis.config",
+                ruleset => elvis_config
+            }
+        ]}
+    ]}
+].
diff --git a/test/style_SUITE.erl b/test/style_SUITE.erl
@@ -55,7 +55,6 @@
     verify_no_import/1,
     verify_no_catch_expressions/1,
     verify_no_single_clause_case/1,
-    verify_no_single_match_maybe/1,
     verify_numeric_format/1,
     verify_behaviour_spelling/1,
     verify_always_shortcircuit/1,
@@ -109,6 +108,12 @@
     verify_elvis_attr_param_pattern_matching/1,
     verify_elvis_attr_private_data_types/1
 ]).
+
+-if(?OTP_RELEASE >= 27).
+-export([
+    verify_no_single_match_maybe/1
+]).
+-endif.
 %% Non-rule
 -export([results_are_ordered_by_line/1, oddities/1]).
 
@@ -172,7 +177,6 @@ groups() ->
             verify_always_shortcircuit,
             verify_no_catch_expressions,
             verify_no_single_clause_case,
-            verify_no_single_match_maybe,
             verify_no_macros,
             verify_export_used_types,
             verify_max_anonymous_function_arity,
@@ -2261,6 +2265,7 @@ verify_no_single_clause_case(Config) ->
                 [#{line_num := 6}, #{line_num := 14}, #{line_num := 16}] = R
         end.
 
+-if(?OTP_RELEASE >= 27).
 -spec verify_no_single_match_maybe(config()) -> any().
 verify_no_single_match_maybe(Config) ->
     Group = proplists:get_value(group, Config, erl_files),
@@ -2279,6 +2284,7 @@ verify_no_single_match_maybe(Config) ->
             erl_files ->
                 [#{line_num := 8}, #{line_num := 16}, #{line_num := 17}] = R
         end.
+-endif.
 
 -spec verify_no_match_in_condition(config()) -> any().
 verify_no_match_in_condition(Config) ->