Credo: how to exclude functions?

Sebb · July 2, 2022, 2:54pm

The checks PipeChainStart and ABC-Size allow a parameter excluded_functions.
This does not seem to work.

https://hexdocs.pm/credo/Credo.Check.Refactor.PipeChainStart.html

I have this function credo does not like:

def hello do
    Kernel.+(1, 1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
    |> Kernel.+(1)
  end

credo complains:

┃ [F] → Function is too complex (ABC size is 31, max is 30).
┃       lib/credo_check.ex:3:7 #(CredoCheck.hello)
┃ [F] → Pipe chain should start with a raw value.
┃       lib/credo_check.ex:5 #(CredoCheck.hello)

with this config:

{Credo.Check.Refactor.PipeChainStart, [excluded_functions: ["hello"]]},
{Credo.Check.Refactor.ABCSize, [excluded_functions: ["hello"]]},

I also tried

:hello
"CredoCheck.hello"
"hello/0"
~r/hello/

al2o3cr · July 2, 2022, 3:31pm

Based on the tests for PipeChainStart, excluded_functions is a list of functions that are allowed to start a chain, not functions that are allowed to have a chain in them:

github.com

rrrene/credo/blob/61a91b0abf3b085f60a41703d2fbcf361b5c1481/test/credo/check/refactor/pipe_chain_start_test.exs#L219-L229


      
          test "it should NOT report a violation for an excluded function call" do
            """
            String.trim("users") |> String.upcase
            """
            |> to_source_file
            |> run_check(
              @described_check,
              excluded_functions: ~w(String.trim table put_in)
            )
            |> refute_issues
          end

You likely want inline config comments on hello instead.

Sebb · July 4, 2022, 3:56pm

thanks for looking into this.

Makes sense for Pipe, but for ABC excluded_functions should exclude functions that are allowed to be complex, right?

al2o3cr · July 4, 2022, 7:07pm

Looks like Pipe has similar functionality, for similar reasons:

github.com

rrrene/credo/blob/61a91b0abf3b085f60a41703d2fbcf361b5c1481/test/credo/check/refactor/abc_size_test.exs#L255-L271


      
          test "it should NOT count functions given to ignore for abc size" do
            source = """
            def fun() do
              Favorite
              |> where(user_id: ^user.id)
              |> join(:left, [f], t in Template, f.entity_id == t.id and f.entity_type == "template")
              |> join(:left, [f, t], d in Document, f.entity_id == d.id and f.entity_type == "document")
              |> join(:left, [f, t, d], dt in Template, dt.id == d.template_id)
              |> join(:left, [f, t, d, dt], c in Category, c.id == t.category_id or c.id == dt.category_id)
              |> select([f, t, d, dt, c], c)
              |> distinct(true)
              |> Repo.all()
            end
            """
          
          
  assert rounded_abc_size(source, ["where", "join", "select", "distinct"]) == 1
          end

ViseLuca · October 27, 2022, 10:50am

Hi but how can I exclude a function?

For example I have

┃ [F] → Pipe chain should start with a raw value.

(row in Transaction)
    |> from(where: &1.id == ^transaction_id)
    |> Worms.Repo.one()

How can I exclude the from function to be warned by credo?

gregvaughn · October 27, 2022, 10:05pm

This may be an unwelcome tangent, but credo would not complain if you wrote this code in the more idiomatic way

Worms.Repo.get(Transaction, transaction_id)

DavidRawk-Blake · September 18, 2023, 7:56am

The example is contrived. I don’t understand how people can’t see this. It’s meant to be silly…

Sometimes a function is only complex if you can’t read. Which is perfectly sane for a linter to catch. But the OP code isn’t complex.