Document previously hidden (though very useful) compiler options

lib/compiler/doc/src/compile.xml

@@ -696,6 +696,20 @@ module.beam: module.erl \
                 fallbacks by accident. Use this option to turn off this kind of
                 warnings.</p>
           </item>
+
+          <tag><c>warn_missing_spec</c></tag>
+          <item>
+              <p>By default, warnings are not emitted when a specification
+                (or contract) for an exported function is not given. Use this
+                option to turn on this kind of warning.</p>
+          </item>
+
+          <tag><c>warn_missing_spec_all</c></tag>
+          <item>
+              <p>By default, warnings are not emitted when a specification
+                (or contract) for an exported or unexported function is not
+                given. Use this option to turn on this kind of warning.</p>
+          </item>
         </taglist>
 
 	<p>Another class of warnings is generated by the compiler

lib/stdlib/test/erl_lint_SUITE.erl

@@ -70,7 +70,8 @@
          otp_14285/1, otp_14378/1,
          external_funs/1,otp_15456/1,otp_15563/1,
          unused_type/1,removed/1, otp_16516/1,
-         inline_nifs/1]).
+         inline_nifs/1,
+         compile_options/1]).
 
 suite() ->
     [{ct_hooks,[ts_install_cth]},
@@ -93,7 +94,7 @@ all() ->
      record_errors, otp_11879_cont, non_latin1_module, otp_14323,
      stacktrace_syntax, otp_14285, otp_14378, external_funs,
      otp_15456, otp_15563, unused_type, removed, otp_16516,
-     inline_nifs].
+     inline_nifs, compile_options].
 
 groups() -> 
     [{unused_vars_warn, [],
@@ -4448,6 +4449,19 @@ inline_nifs(Config) ->
            {warnings,[{2,erl_lint,nif_inline}]}}],
     [] = run(Config, Ts).
 
+compile_options(Config) ->
+    WOkay = get_compilation_result(Config, "warn_missing_spec_ok", [warn_missing_spec]),
+    [] = WOkay,
+
+    WError = get_compilation_result(Config, "warn_missing_spec_error", [warn_missing_spec]),
+    [_] = WError,
+
+    WAllOkay = get_compilation_result(Config, "warn_missing_spec_all_ok", [warn_missing_spec_all]),
+    [] = WAllOkay,
+
+    WAllError = get_compilation_result(Config, "warn_missing_spec_all_error", [warn_missing_spec_all]),
+    [_] = WAllError.
+
 format_error(E) ->
     lists:flatten(erl_lint:format_error(E)).
 

lib/stdlib/test/erl_lint_SUITE_data/warn_missing_spec_all_error.erl

@@ -0,0 +1,27 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2020. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(erlc_test_warn_missing_spec_all_error).
+
+-export([external/0]).
+
+external() -> internal().
+
+-spec internal() -> ok.
+internal() -> ok.

lib/stdlib/test/erl_lint_SUITE_data/warn_missing_spec_all_ok.erl

@@ -0,0 +1,28 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2020. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(erlc_test_warn_missing_spec_all_ok).
+
+-export([external/0]).
+
+-spec external() -> ok.
+external() -> internal().
+
+-spec internal() -> ok.
+internal() -> ok.

lib/stdlib/test/erl_lint_SUITE_data/warn_missing_spec_error.erl

@@ -0,0 +1,27 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2020. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(erlc_test_warn_missing_spec_error).
+
+-export([external/0]).
+
+external() -> internal().
+
+-spec internal() -> ok.
+internal() -> ok.

lib/stdlib/test/erl_lint_SUITE_data/warn_missing_spec_ok.erl

@@ -0,0 +1,27 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2020. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(erlc_test_warn_missing_spec_ok).
+
+-export([external/0]).
+
+-spec external() -> ok.
+external() -> internal().
+
+internal() -> ok.