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Elixir - Credo

07 Jan 2018
  1. https://github.com/rrrene/credo

configuration

generate Credo config

$ mix credo gen.config

generated config contains all Credo checks with default params.

usage

run Credo

suggestions + style guide on a per file basis:

$ mix credo list --strict

by default low priority issues are not shown - --all-priorities switch (aliased as --strict) allows to include them in the output => there are no special style guide checks enabled by this option.

explain specific issue (explain is a default command when filename:line_number:column string is passed):

$ mix credo lib/neko/user_handler.ex:66:5
$ mix credo explain lib/neko/user_handler.ex:66:5

disable check

  # .credo.exs

- {Credo.Check.Refactor.PipeChainStart, []},
+ {Credo.Check.Refactor.PipeChainStart, false},

ignore Credo errors on a one-off basis

# credo:disable-for-this-file
# credo:disable-for-this-file Credo.Check.Refactor.PipeChainStart

# credo:disable-for-next-line
Registry.fetch(user_id) |> Store.reload(user_id)
# credo:disable-for-next-line Credo.Check.Refactor.PipeChainStart
Registry.fetch(user_id) |> Store.reload(user_id)
# credo:disable-for-lines:2
MapSet.new(list_1)
|> MapSet.intersection(MapSet.new(list_2))

it’s not required to re-enable checks just like for Rubocop.

Vim integration

ale

~/.vim/vimrc:

let g:ale_linters = {
      \   'elixir': ['credo']
      \ }

ALE runs this command for credo linter: mix credo suggest --format=flycheck --read-from-stdin %s.

the main point is that --strict option is missing so low priority issues won’t displayed by ALE.

this can be circumvented, if required, globally by switching to strict mode (= show issues of all priorities):

  # .credo.exs

  %{
    configs: [
      %{
        # ...
-       strict: false,
+       strict: true,
        # ...
      }
    ]
  }

or by changing priority of check of interest:

  # .credo.exs

- {Credo.Check.Readability.MaxLineLength, priority: :low, max_length: 80},
+ {Credo.Check.Readability.MaxLineLength, priority: :normal, max_length: 80},

notes

check priorities

.credo.exs:

Priority values are: low, normal, high, higher

each Credo check has its own default priority, priority of any check can be customized with priority parameter in .credo.exs:

{Credo.Check.Design.AliasUsage, priority: :low},

issue categories

$ mix credo categories