filter_reject.ex (1199B)
1 defmodule Credo.Check.Refactor.FilterReject do 2 use Credo.Check, 3 tags: [:controversial], 4 explanations: [ 5 check: """ 6 One `Enum.filter/2` is more efficient than `Enum.filter/2 |> Enum.reject/2`. 7 8 This should be refactored: 9 10 ["a", "b", "c"] 11 |> Enum.filter(&String.contains?(&1, "x")) 12 |> Enum.reject(&String.contains?(&1, "a")) 13 14 to look like this: 15 16 Enum.filter(["a", "b", "c"], fn letter -> 17 String.contains?(letter, "x") && !String.contains?(letter, "a") 18 end) 19 20 The reason for this is performance, because the two calls to 21 `Enum.reject/2` and `Enum.filter/2` require two iterations whereas 22 doing the functions in the single `Enum.filter/2` only requires one. 23 """ 24 ] 25 26 alias Credo.Check.Refactor.EnumHelpers 27 28 @doc false 29 def run(source_file, params \\ []) do 30 issue_meta = IssueMeta.for(source_file, params) 31 32 message = "One `Enum.filter/2` is more efficient than `Enum.filter/2 |> Enum.reject/2`" 33 trigger = "|>" 34 35 Credo.Code.prewalk( 36 source_file, 37 &EnumHelpers.traverse(&1, &2, issue_meta, message, trigger, :filter, :reject, __MODULE__) 38 ) 39 end 40 end