ExSlop.Check.Refactor.LengthComparison (ExSlop v0.4.2)

Basics

This check has a base priority of normal and works with any version of Elixir.

Explanation

Comparing length/1 against an integer literal walks the whole list just to answer a question about its size.

Unlike LengthInGuard, this fires in any context — guard or body — so moving the comparison out of a guard into an if does not hide the problem, it just relocates it.

# bad
if length(list) == 0, do: :empty
def page(list) when length(list) > 0, do: ...
length(items) <= 5

# good — emptiness
if list == [], do: :empty          # or Enum.empty?(list)
def page([_ | _]), do: ...

# good — exact/maximum size
case list do
  [_, _] -> ...
end

# good — threshold on a large or lazy enum
Enum.count_until(items, 6) <= 5

length/1 itself is fine when you genuinely need the count (logging, arithmetic, a value you reuse) — only the comparison against a literal is flagged.

Check-Specific Parameters

There are no specific parameters for this check.

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.