Ignore return value of Lager log functions

To work around erlang-lager/lager#546 which blocks
OTP 24 compatibility work in projects that use Lager.

For Cuttlefish, explicitly ignoring return values is a practical
option.

src/cuttlefish.erl

@@ -123,7 +123,7 @@ invalid(Reason) ->
 %% being logged.
 -spec warn(iodata()) -> ok.
 warn(Str) ->
-    lager:warning(Str, []).
+    _ = lager:warning(Str, []).
 
 -ifdef(TEST).
 

src/cuttlefish_conf.erl

@@ -139,7 +139,7 @@ generate_file(Mappings, Filename) ->
     _ = [ begin
           io:format(S, "~s~n", [lists:flatten(Line)])
       end || Line <- ConfFileLines],
-    % add an include directive at the end that will allow 
+    % add an include directive at the end that will allow
     % other conf files in `conf.d` and have them get picked up
     % in order to override settings
     % example use case is a k8s configMap that is mapped as a file
@@ -168,7 +168,7 @@ generate_element(MappingRecord) ->
     case Level of
         basic -> ok;
         Level ->
-            lager:warning("{level, ~p} has been deprecated. Use 'hidden' or '{hidden, true}'", [Level])
+            _ = lager:warning("{level, ~p} has been deprecated. Use 'hidden' or '{hidden, true}'", [Level])
     end,
 
     case generate_element(Hidden, Level, Default, Commented) of

src/cuttlefish_error.erl

@@ -177,7 +177,7 @@ print(FormatString, Args) ->
 print({error, ErrorTerm}) ->
     print(lists:flatten(xlate(ErrorTerm)));
 print(String) ->
-    case lager:error("~s", [String]) of
+    case _ = lager:error("~s", [String]) of
         {error, lager_not_running} ->
             io:format("~s~n", [String]),
             ok;

src/cuttlefish_escript.erl

@@ -85,9 +85,9 @@ main(Args) ->
     application:set_env(lager, handlers, [{lager_stderr_backend, LogLevel}]),
     application:set_env(lager, crash_log, false),
     lager:start(),
-    lager:debug("Cuttlefish set to debug level logging"),
+    _ = lager:debug("Cuttlefish set to debug level logging"),
 
-    lager:debug("Parsed arguments: ~p", [ParsedArgs]),
+    _ = lager:debug("Parsed arguments: ~p", [ParsedArgs]),
 
     case Command of
         help ->
@@ -104,7 +104,7 @@ main(Args) ->
 
 %% This shows the effective configuration, including defaults
 effective(ParsedArgs) ->
-    lager:debug("cuttlefish `effective`", []),
+    _ = lager:debug("cuttlefish `effective`", []),
     EtcDir = proplists:get_value(etc_dir, ParsedArgs),
 
     %% Should we even show this?
@@ -114,15 +114,15 @@ effective(ParsedArgs) ->
     case {AppConfigExists, VMArgsExists} of
         {false, false} ->
             AdvancedConfigFile = proplists:get_value(advanced_conf_file, ParsedArgs, filename:join(EtcDir, "advanced.config")),
-            lager:debug("Will look for advanced.config at '~s'", [AdvancedConfigFile]),
+            _ = lager:debug("Will look for advanced.config at '~s'", [AdvancedConfigFile]),
             AdvConfig = case filelib:is_file(AdvancedConfigFile) of
                 true ->
-                    lager:debug("~s detected, overlaying proplists", [AdvancedConfigFile]),
+                    _ = lager:debug("~s detected, overlaying proplists", [AdvancedConfigFile]),
                     case file:consult(AdvancedConfigFile) of
                         {ok, [AdvancedConfig]} ->
                             AdvancedConfig;
                         {error, Error} ->
-                            lager:error("Error parsing advanced.config: ~s", [file:format_error(Error)]),
+                            _ = lager:error("Error parsing advanced.config: ~s", [file:format_error(Error)]),
                             stop_deactivate()
                     end;
                 _ ->
@@ -162,7 +162,7 @@ describe(_ParsedArgs, []) ->
 describe(ParsedArgs, [Query|_]) when is_list(Query) ->
     QDef = cuttlefish_variable:tokenize(Query),
 
-    lager:debug("cuttlefish describe '~s'", [Query]),
+    _ = lager:debug("cuttlefish describe '~s'", [Query]),
     {_, Mappings, _} = load_schema(ParsedArgs),
 
     FindResults = fun(QueryVar) ->
@@ -249,20 +249,20 @@ generate(ParsedArgs) ->
     %% even though cuttlefish is awesome
     FilesToUse = case {AppConfigExists, VMArgsExists} of
         {true, true} ->
-            lager:info("~s and ~s exists, disabling cuttlefish.", [ExistingAppConfigName, ExistingVMArgsName]),
-            lager:info("If you'd like to know more about cuttlefish, check your local library!", []),
-            lager:info(" or see http://github.com/Kyorai/cuttlefish", []),
+            _ = lager:info("~s and ~s exists, disabling cuttlefish.", [ExistingAppConfigName, ExistingVMArgsName]),
+            _ = lager:info("If you'd like to know more about cuttlefish, check your local library!", []),
+            _ = lager:info(" or see http://github.com/Kyorai/cuttlefish", []),
             {ExistingAppConfigName, ExistingVMArgsName};
         {true, false} ->
-            lager:info("~s exists, generating vm.args", [ExistingAppConfigName]),
+            _ = lager:info("~s exists, generating vm.args", [ExistingAppConfigName]),
             {_, NewVMArgs} = engage_cuttlefish(ParsedArgs),
             {ExistingAppConfigName, NewVMArgs};
         {false, true} ->
-            lager:info("~s exists, generating app.config", [ExistingVMArgsName]),
+            _ = lager:info("~s exists, generating app.config", [ExistingVMArgsName]),
             {NewAppConfig, _} = engage_cuttlefish(ParsedArgs),
             {NewAppConfig, ExistingVMArgsName};
         _ ->
-            lager:info("No app.config or vm.args detected in ~s, activating cuttlefish", [EtcDir]),
+            _ = lager:info("No app.config or vm.args detected in ~s, activating cuttlefish", [EtcDir]),
             engage_cuttlefish(ParsedArgs)
     end,
 
@@ -297,10 +297,10 @@ load_schema(ParsedArgs) ->
     SortedSchemaFiles = lists:sort(fun(A,B) -> A < B end, SchemaFiles),
     case length(SortedSchemaFiles) of
         0 ->
-            lager:debug("No Schema files found in specified", []),
+            _ = lager:debug("No Schema files found in specified", []),
             stop_deactivate();
         _ ->
-            lager:debug("SchemaFiles: ~p", [SortedSchemaFiles])
+            _ = lager:debug("SchemaFiles: ~p", [SortedSchemaFiles])
     end,
 
     Schema = cuttlefish_schema:files(SortedSchemaFiles),
@@ -314,10 +314,10 @@ load_schema(ParsedArgs) ->
 
 load_conf(ParsedArgs) ->
     ConfFiles = proplists:get_all_values(conf_file, ParsedArgs),
-    lager:debug("ConfFiles: ~p", [ConfFiles]),
+    _ = lager:debug("ConfFiles: ~p", [ConfFiles]),
     case cuttlefish_conf:files(ConfFiles) of
         {errorlist, Errors} ->
-            _ = [ lager:error(cuttlefish_error:xlate(E)) ||
+            _ = [ _ = lager:error(cuttlefish_error:xlate(E)) ||
                     {error, E} <- Errors],
             stop_deactivate(),
             {errorlist, Errors};
@@ -340,7 +340,7 @@ writable_destination_path(ParsedArgs) ->
         ok ->
             AbsoluteDestPath;
         {error, E} ->
-            lager:error(
+            _ = lager:error(
                 "Error creating ~s: ~s",
                 [AbsoluteDestPath, file:format_error(E)]),
             error
@@ -363,32 +363,32 @@ engage_cuttlefish(ParsedArgs) ->
     DestinationVMArgsFilename = filename_maker(proplists:get_value(dest_file, ParsedArgs, "vm"), "args"),
     DestinationVMArgs = filename:join(AbsPath, DestinationVMArgsFilename),
 
-    lager:debug("Generating config in: ~p", [Destination]),
-    lager:debug("Generating vm.args in: ~p", [DestinationVMArgs]),
+    _ = lager:debug("Generating config in: ~p", [Destination]),
+    _ = lager:debug("Generating vm.args in: ~p", [DestinationVMArgs]),
 
     Schema = load_schema(ParsedArgs),
     Conf = load_conf(ParsedArgs),
     NewConfig = case cuttlefish_generator:map(Schema, Conf, ParsedArgs) of
         {error, Phase, {errorlist, Errors}} ->
-            lager:error("Error generating configuration in phase ~s", [Phase]),
+            _ = lager:error("Error generating configuration in phase ~s", [Phase]),
             _ = [ cuttlefish_error:print(E) || E <- Errors],
             stop_deactivate();
         ValidConfig -> ValidConfig
     end,
 
     AdvancedConfigFile = proplists:get_value(advanced_conf_file, ParsedArgs, filename:join(EtcDir, "advanced.config")),
-    lager:debug("AdvancedConfigFile: ~p", [AdvancedConfigFile]),
+    _ = lager:debug("AdvancedConfigFile: ~p", [AdvancedConfigFile]),
     FinalConfig = case filelib:is_file(AdvancedConfigFile) of
         true ->
-            lager:info("advanced config file is detected at ~s, overlaying proplists", [AdvancedConfigFile]),
+            _ = lager:info("advanced config file is detected at ~s, overlaying proplists", [AdvancedConfigFile]),
             case file:consult(AdvancedConfigFile) of
                 {ok, [AdvancedConfig]} ->
                     cuttlefish_advanced:overlay(NewConfig, AdvancedConfig);
                 {ok, OtherTerms} ->
-                    lager:error("Error parsing ~s, incorrect format: ~p", [AdvancedConfigFile, OtherTerms]),
+                    _ = lager:error("Error parsing ~s, incorrect format: ~p", [AdvancedConfigFile, OtherTerms]),
                     stop_deactivate();
                 {error, Error} ->
-                    lager:error("Error parsing ~s: ~s", [AdvancedConfigFile, file:format_error(Error)]),
+                    _ = lager:error("Error parsing ~s: ~s", [AdvancedConfigFile, file:format_error(Error)]),
                     stop_deactivate()
             end;
         _ ->
@@ -450,7 +450,7 @@ delete([File|Files], MaxHistory) ->
     case file:delete(File) of
         ok -> ok;
         {error, Reason} ->
-            lager:error("Could not delete ~s, ~p", [File, Reason])
+            _ = lager:error("Could not delete ~s, ~p", [File, Reason])
     end,
     delete(Files, MaxHistory).
 
@@ -464,14 +464,14 @@ delete([File|Files], MaxHistory) ->
 maybe_log_file_error(_, ok) ->
     ok;
 maybe_log_file_error(Filename, {error, Reason}) ->
-    lager:error("Error writing ~s: ~s", [Filename, file:format_error(Reason)]),
+    _ = lager:error("Error writing ~s: ~s", [Filename, file:format_error(Reason)]),
     ok.
 
 -spec check_existence(string(), string()) -> {boolean(), string()}.
 check_existence(EtcDir, Filename) ->
     FullName = filename:join(EtcDir, Filename), %% Barfolomew
     Exists = filelib:is_file(FullName),
-    lager:info("Checking ~s exists... ~p", [FullName, Exists]),
+    _ = lager:info("Checking ~s exists... ~p", [FullName, Exists]),
     {Exists, FullName}.
 
 filename_maker(Filename, Extension) ->
@@ -503,7 +503,7 @@ zero_pad(Integer) ->
     end.
 
 print_schema(Schema) ->
-    lager:info("Printing Schema Mappings"),
+    _ = lager:info("Printing Schema Mappings"),
     {_, Mappings, _} = Schema,
 
     {Max, ListOfMappings} = lists:foldr(

src/cuttlefish_generator.erl

@@ -74,7 +74,7 @@ restrict_mappings(M, {Mappings, Keys}, ConfigKeys) ->
 map_add_defaults({_, Mappings, _} = Schema, Config, ParsedArgs) ->
     %% Config at this point is just what's in the .conf file.
     %% add_defaults/2 rolls the default values in from the schema
-    lager:debug("Adding Defaults"),
+    _ = lager:debug("Adding Defaults"),
     DConfig = add_defaults(Config, Mappings),
     case cuttlefish_error:errorlist_maybe(DConfig) of
         {errorlist, EList} ->
@@ -87,7 +87,7 @@ map_add_defaults({_, Mappings, _} = Schema, Config, ParsedArgs) ->
                            [proplists:property()] |
                            {error, atom(), cuttlefish_error:errorlist()}.
 map_value_sub(Schema, Config, ParsedArgs) ->
-    lager:debug("Right Hand Side Substitutions"),
+    _ = lager:debug("Right Hand Side Substitutions"),
      case value_sub(Config) of
          {SubbedConfig, []} ->
             map_transform_datatypes(Schema, SubbedConfig, ParsedArgs);
@@ -102,7 +102,7 @@ map_transform_datatypes({_, Mappings, _} = Schema, DConfig, ParsedArgs) ->
     %% Everything in DConfig is of datatype "string",
     %% transform_datatypes turns them into other erlang terms
     %% based on the schema
-    lager:debug("Applying Datatypes"),
+    _ = lager:debug("Applying Datatypes"),
     case transform_datatypes(DConfig, Mappings, ParsedArgs) of
         {NewConf, []} ->
             map_validate(Schema, NewConf);
@@ -115,7 +115,7 @@ map_transform_datatypes({_, Mappings, _} = Schema, DConfig, ParsedArgs) ->
                           {error, atom(), cuttlefish_error:errorlist()}.
 map_validate(Schema, Conf) ->
     %% Any more advanced validators
-    lager:debug("Validation"),
+    _ = lager:debug("Validation"),
     case cuttlefish_error:errorlist_maybe(run_validations(Schema, Conf)) of
         {errorlist, EList} ->
             {error, validation, {errorlist, EList}};
@@ -160,7 +160,7 @@ apply_mappings({Translations, Mappings, _Validators}, Conf) ->
         end,
         {[], {ordsets:new(),ordsets:new()}},
         Mappings),
-    lager:debug("Applied 1:1 Mappings"),
+    _ = lager:debug("Applied 1:1 Mappings"),
 
     TranslationsToDrop = TranslationsToMaybeDrop -- TranslationsToKeep,
     {DirectMappings, TranslationsToDrop}.
@@ -176,7 +176,7 @@ apply_translations({Translations, _, _} = Schema, Conf, DirectMappings, Translat
                                         {DirectMappings, []}, Translations),
     case Errorlist of
         [] ->
-            lager:debug("Applied Translations"),
+            _ = lager:debug("Applied Translations"),
             Proplist;
         Es ->
             {error, apply_translations, {errorlist, Es}}
@@ -191,7 +191,7 @@ fold_apply_translation(Conf, Schema, TranslationsToDrop) ->
                 false ->
                     {XlatFun, XlatArgs} = prepare_translation_fun(Conf, Schema,
                                                                   Mapping, Xlat),
-                    lager:debug("Running translation for ~s", [Mapping]),
+                    _ = lager:debug("Running translation for ~s", [Mapping]),
                     case try_apply_translation(Mapping, XlatFun, XlatArgs) of
                         unset ->
                             {Acc, Errors};
@@ -201,7 +201,7 @@ fold_apply_translation(Conf, Schema, TranslationsToDrop) ->
                             {Acc, [{error, Term}|Errors]}
                     end;
                 _ ->
-                    lager:debug("~p in Translations to drop...", [Mapping]),
+                    _ = lager:debug("~p in Translations to drop...", [Mapping]),
                     {Acc, Errors}
             end
         end.
@@ -300,7 +300,7 @@ add_default(Conf, Prefixes, MappingRecord, Acc) ->
         %% If Match =:= true, do nothing, the value is set in the .conf file
         _ ->
             %% TODO: Handle with more style and grace
-            lager:error("Both fuzzy and strict match! should not happen"),
+            _ = lager:error("Both fuzzy and strict match! should not happen"),
             [{error, {map_multiple_match, VariableDef}}|Acc]
     end.
 
@@ -415,15 +415,15 @@ transform_datatypes(Conf, Mappings, ParsedArgs) ->
                     %% It will prevent anything from starting, and will let you know
                     %% that you're trying to set something that has no effect
                     VarName = cuttlefish_variable:format(Variable),
-                    lager:error("You've tried to set ~s, but there is no setting with that name.", [VarName]),
-                    lager:error("  Did you mean one of these?"),
+                    _ = lager:error("You've tried to set ~s, but there is no setting with that name.", [VarName]),
+                    _ = lager:error("  Did you mean one of these?"),
 
                     Possibilities = [ begin
                         MapVarName = cuttlefish_variable:format(cuttlefish_mapping:variable(M)),
                         {cuttlefish_util:levenshtein(VarName, MapVarName), MapVarName}
                     end || M <- Mappings],
                     Sorted = lists:sort(Possibilities),
-                    _ = [ lager:error("    ~s", [T]) || {_, T} <- lists:sublist(Sorted, 3) ],
+                    _ = [ _ = lager:error("    ~s", [T]) || {_, T} <- lists:sublist(Sorted, 3) ],
                     {Acc, [ {error, {unknown_variable, VarName}} | ErrorAcc ]};
                 MappingRecord ->
                     DTs = cuttlefish_mapping:datatype(MappingRecord),
@@ -622,7 +622,7 @@ run_validations({_, Mappings, Validators}, Conf) ->
                                              cuttlefish_mapping:variable(M)),
                                            cuttlefish_validator:description(V)
                                          }},
-                    lager:error(cuttlefish_error:xlate(Error)),
+                    _ = lager:error(cuttlefish_error:xlate(Error)),
                     {error, Error}
             end
         end || V <- Vs]

src/cuttlefish_schema.erl

@@ -156,7 +156,7 @@ string(S, {T, M, V}) ->
         {error, {Line, erl_scan, _}, _} ->
             Error = {erl_scan, Line},
             ErrStr = cuttlefish_error:xlate(Error),
-            lager:error(lists:flatten(ErrStr)),
+            _ = lager:error(lists:flatten(ErrStr)),
             {errorlist, [{error, Error}]}
     end.
 

src/cuttlefish_unit.erl

@@ -180,7 +180,7 @@ multiple_schema_generate_templated_config_test() ->
                         ], []},
 
     Config = cuttlefish_unit:generate_templated_config("test/sample_mustache.schema", [], Context, PrereqSchema),
-    lager:error("~p", [Config]),
+    _ = lager:error("~p", [Config]),
     assert_config(Config, "app_a.setting_b", "/c/mustache/a.b"),
     ok.
 

src/cuttlefish_util.erl

@@ -43,27 +43,27 @@
 
 %% @deprecated
 conf_get_value(Key, Conf) ->
-    lager:warning("cuttlefish_util:conf_get_value/2 has been deprecated. use cuttlefish:conf_get/2"),
+    _ = lager:warning("cuttlefish_util:conf_get_value/2 has been deprecated. use cuttlefish:conf_get/2"),
     cuttlefish:conf_get(Key, Conf).
 
 %% @deprecated
 conf_get_value(Key, Conf, Default) ->
-    lager:warning("cuttlefish_util:conf_get_value/3 has been deprecated. use cuttlefish:conf_get/3"),
+    _ = lager:warning("cuttlefish_util:conf_get_value/3 has been deprecated. use cuttlefish:conf_get/3"),
     cuttlefish:conf_get(Key, Conf, Default).
 
 %% @deprecated
 filter_by_variable_starts_with(Prefix, Conf) ->
-    lager:warning("cuttlefish_util:filter_by_variable_starts_with/2 has been deprecated. use cuttlefish_variable:filter_by_prefix/2"),
+    _ = lager:warning("cuttlefish_util:filter_by_variable_starts_with/2 has been deprecated. use cuttlefish_variable:filter_by_prefix/2"),
     cuttlefish_variable:filter_by_prefix(Prefix, Conf).
 
 %% @deprecated
 matches_for_variable_def(VarDef, Conf) ->
-    lager:warning("cuttlefish_util:matches_for_variable_def/2 has been deprecated. use cuttlefish_variable:fuzzy_matches/2"),
+    _ = lager:warning("cuttlefish_util:matches_for_variable_def/2 has been deprecated. use cuttlefish_variable:fuzzy_matches/2"),
     cuttlefish_variable:fuzzy_matches(VarDef, Conf).
 
 %% @deprecated
 fuzzy_variable_match(Var, VarDef) ->
-    lager:warning("cuttlefish_util:fuzzy_variable_match/2 has been deprecated. use cuttlefish_variable:is_fuzzy_match/2"),
+    _ = lager:warning("cuttlefish_util:fuzzy_variable_match/2 has been deprecated. use cuttlefish_variable:is_fuzzy_match/2"),
     cuttlefish_variable:is_fuzzy_match(Var, VarDef).
 
 %% @doc replace the element in a proplist
@@ -172,7 +172,7 @@ levenshtein_test() ->
 
 print_error_test() ->
     application:stop(lager),
-    case lager:error("Error") of
+    case _ = lager:error("Error") of
         {error, lager_not_running} ->
             ?assertEqual(ok, (cuttlefish_error:print("Error")));
         Other ->