defmodule Credo.Check.Refactor.FilterReject do
use Credo.Check,
id: "EX4009",
tags: [:controversial],
explanations: [
check: """
One `Enum.filter/2` is more efficient than `Enum.filter/2 |> Enum.reject/2`.
This should be refactored:
["a", "b", "c"]
|> Enum.filter(&String.contains?(&1, "x"))
|> Enum.reject(&String.contains?(&1, "a"))
to look like this:
Enum.filter(["a", "b", "c"], fn letter ->
String.contains?(letter, "x") && !String.contains?(letter, "a")
end)
The reason for this is performance, because the two calls to
`Enum.reject/2` and `Enum.filter/2` require two iterations whereas
doing the functions in the single `Enum.filter/2` only requires one.
"""
]
alias Credo.Check.Refactor.EnumHelpers
@doc false
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
message = "One `Enum.filter/2` is more efficient than `Enum.filter/2 |> Enum.reject/2`"
trigger = "|>"
Credo.Code.prewalk(
source_file,
&EnumHelpers.traverse(&1, &2, issue_meta, message, trigger, :filter, :reject, __MODULE__)
)
end
end