Readability checks fail for shorthand module definitions

[jjcarstens]

Environment

• Credo version (mix credo -v): 1.6.4
• Erlang/Elixir version (elixir -v): 1.13.3 OTP 24.3.3
• Operating system: MacOS 12.3

What were you trying to do?

This might be totally out of scope, but I find it interesting non-the-less.

I have a really simple one-liner module definition in a file. Something like

defmodule Person, do: def greet(), do: :howdy

Technically valid Elixir (arguably code smell 🥴 ), and it crashes during Elixir.Credo.Check.Readability.* checks.

Log output

> firmware √ % mix credo                                                                                                                                                                                                                               CB-87-test-firmware
Checking 26 source files ...
Error while running Elixir.Credo.Check.Readability.Specs on test/support/test.ex
Error while running Elixir.Credo.Check.Readability.ModuleDoc on test/support/test.ex

14:38:15.333 [error] Task #PID<0.498.0> started from #PID<0.395.0> terminating
** (ArithmeticError) bad argument in arithmetic expression
    :erlang.+(1, nil)
    (credo 1.6.4) lib/credo/priority.ex:83: anonymous fn/2 in Credo.Priority.scope_priorities/1
    (elixir 1.13.3) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.13.3) lib/enum.ex:1496: Enum.into/3
    (credo 1.6.4) lib/credo/check.ex:714: Credo.Check.priority_for/2
    (credo 1.6.4) lib/credo/check.ex:654: Credo.Check.add_line_no_options/3
    (credo 1.6.4) lib/credo/check.ex:624: Credo.Check.format_issue/5
    (credo 1.6.4) lib/credo/check/readability/module_doc.ex:87: Credo.Check.Readability.ModuleDoc.traverse/4
Function: #Function<5.41562928/0 in Credo.Check.Readability.ModuleDoc.do_run_on_all_source_files/3>
    Args: []

14:38:15.333 [error] Task #PID<0.1815.0> started from #PID<0.1763.0> terminating
** (ArithmeticError) bad argument in arithmetic expression
    :erlang.+(1, nil)
    (credo 1.6.4) lib/credo/priority.ex:83: anonymous fn/2 in Credo.Priority.scope_priorities/1
    (elixir 1.13.3) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.13.3) lib/enum.ex:1496: Enum.into/3
    (credo 1.6.4) lib/credo/check.ex:714: Credo.Check.priority_for/2
    (credo 1.6.4) lib/credo/check.ex:654: Credo.Check.add_line_no_options/3
    (credo 1.6.4) lib/credo/check.ex:624: Credo.Check.format_issue/5
    (credo 1.6.4) lib/credo/check/readability/specs.ex:104: Credo.Check.Readability.Specs.traverse/4
Function: #Function<5.24813483/0 in Credo.Check.Readability.Specs.do_run_on_all_source_files/3>
    Args: []
** (EXIT from #PID<0.93.0>) an exception was raised:
    ** (ArithmeticError) bad argument in arithmetic expression
        :erlang.+(1, nil)
        (credo 1.6.4) lib/credo/priority.ex:83: anonymous fn/2 in Credo.Priority.scope_priorities/1
        (elixir 1.13.3) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
        (elixir 1.13.3) lib/enum.ex:1496: Enum.into/3
        (credo 1.6.4) lib/credo/check.ex:714: Credo.Check.priority_for/2
        (credo 1.6.4) lib/credo/check.ex:654: Credo.Check.add_line_no_options/3
        (credo 1.6.4) lib/credo/check.ex:624: Credo.Check.format_issue/5
        (credo 1.6.4) lib/credo/check/readability/specs.ex:104: Credo.Check.Readability.Specs.traverse/4

Oddly enough, I can successfully get past it by actually including the moduledoc

defmodule Test, do: @moduledoc "why though?!"; def test(), do: :howdy

I don't even know if I would call this a bug or expect a fix, so do what you will with this issue. It's at least interesting and maybe useful for posterity 😉

[rrrene]

Judging from the log, this might actually highlight a deeper issue.

Thx for reporting! 👍

[rrrene]

Thx for reporting this! 👍 It should be be fixed in the latest version of Credo.

If it is not, please feel free to re-open this issue!