kernel: Fix code:get_doc/1,2 when cover_compiled

[williamthome]

This PR fixes a bug getting docs when a module is compiled by the cover module. Also, the cover_compiled error was missing in the spec.

To reproduce, first compile the module via cover:compile and run code:get_doc.

Find this bug via the new doctest, for example:

% src/otp_doctest
-module(otp_doctest).

-export([foo/0]).

-doc ~"""
```
> otp_doctest:foo().
bar % must fail
```
""".
foo() ->
    foo.

% rebar.config
{profiles, [
    {test, [
        {cover_enabled, true}
    ]}
]}.

% test/otp_doctest_SUITE.erl
-module(otp_doctest_SUITE).
-behaviour(ct_suite).
-compile([export_all, nowarn_export_all]).

all() ->
    [doctests].

doctests(Config) when is_list(Config) ->
    shell_docs:test(otp_doctest, []).

The expected result is to fail, but the test passed:

$ rebar3 ct
===> Verifying dependencies...
===> Analyzing applications...
===> Compiling otp_doctest
===> Running Common Test suites...
%%% otp_doctest_SUITE: .
All 1 tests passed.

After this PR the error is raised:

===> Verifying dependencies...
===> Analyzing applications...
===> Compiling otp_doctest
===> Running Common Test suites...
%%% otp_doctest_SUITE:
%%% otp_doctest_SUITE ==> doctests: FAILED
%%% otp_doctest_SUITE ==> {{badmatch,foo},
 [{erl_eval,expr,6,[{file,"erl_eval.erl"},{line,670}]},
  {shell_docs_test,run_tests,2,[{file,"shell_docs_test.erl"},{line,198}]},
  {lists,foldl,3,[{file,"lists.erl"},{line,2150}]},
  {shell_docs_test,test,2,[{file,"shell_docs_test.erl"},{line,153}]},
  {shell_docs_test,parse_and_run,3,[{file,"shell_docs_test.erl"},{line,137}]},
  {shell_docs_test,'-parse_and_run/3-lc$^0/1-0-',3,
                   [{file,"shell_docs_test.erl"},{line,133}]},
  {shell_docs_test,'-module/2-lc$^0/1-0-',3,
                   [{file,"shell_docs_test.erl"},{line,122}]},
  {shell_docs_test,module,2,[{file,"shell_docs_test.erl"},{line,123}]}]}

cc @garazdawi

[github-actions]

CT Test Results

    3 files    392 suites   1h 14m 23s ⏱️
2 305 tests 2 063 ✅ 241 💤 1 ❌
7 298 runs  7 005 ✅ 292 💤 1 ❌

For more details on these failures, see this check.

Results for commit 06adfb2.

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// Erlang/OTP Github Action Bot

[williamthome]

I think this fix should be in the maint branch, but I changed the base branch and a bunch of commits appeared in this PR.

[bjorng]

Thanks for your pull request.

Please add a test case to beam_doc_SUITE in the compiler application.

[michalmuskala]

As a side point, I wonder if rebar3 should switch how it uses cover, to just compiling the code in the first place with the appropriate flags, rather than dynamically recompiling it - it's much faster and avoids issues like this - it was one of the reasons to add the new coverage system - it doesn't require dynamic recompilation.

[williamthome]

Please add a test case to beam_doc_SUITE in the compiler application.

Done.

[bjorng]

I pushed a fixup commit that fixed a few issues. If you agree, please squash the commits.

• A test case that changes the working directory is usually not safe to run in a group concurrently with other test cases. For me, one to four test cases failed each time I ran beam_doc_SUITE.
• If Cover is already running, the test case must be skipped. We often run the compiler tests with Cover enabled.
• Cover must be stopped when done, irregardless of whether the test case failed or not.

[williamthome]

I pushed a fixup commit that fixed a few issues. If you agree, please squash the commits.

• A test case that changes the working directory is usually not safe to run in a group concurrently with other test cases. For me, one to four test cases failed each time I ran beam_doc_SUITE.
• If Cover is already running, the test case must be skipped. We often run the compiler tests with Cover enabled.
• Cover must be stopped when done, irregardless of whether the test case failed or not.

Agree and squashed. Thank you for the fix and explanation!

[bjorng]

Added to our daily builds.

[bjorng]

I forgot to run Dialyzer before I pushed my suggestion for simpler implementation. It turns out that one clause will never match. I've pushed a new fixup commit. Please squash.

[williamthome]

Please squash.

Done.

[bjorng]

Thanks for your pull request.