Credo
Credo v1.6.7

View Source Credo.Check.Refactor.NegatedConditionsWithElse (Credo v1.6.7)

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

Explanation

An if block with a negated condition should not contain an else block.

So while this is fine:

if not allowed? do
  raise "Not allowed!"
end

The code in this example ...

if not allowed? do
  raise "Not allowed!"
else
  proceed_as_planned()
end

... should be refactored to look like this:

if allowed? do
  proceed_as_planned()
else
  raise "Not allowed!"
end

The same goes for negation through ! instead of not.

The reason for this is not a technical but a human one. It is easier to wrap your head around a positive condition and then thinking "and else we do ...".

In the above example raising the error in case something is not allowed might seem so important to put it first. But when you revisit this code a while later or have to introduce a colleague to it, you might be surprised how much clearer things get when the "happy path" comes first.

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.