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lib/credo/check/readability/parentheses_in_condition.ex

defmodule Credo.Check.Readability.ParenthesesInCondition do
@moduledoc """
Because `if` and `unless` are macros, the preferred style is to not use
parentheses around conditions.
# preferred way
if valid?(username) do
# ...
end
# NOT okay
if( valid?(username) ) do
# ...
end
Like all `Readability` issues, this one is not a technical concern.
But you can improve the odds of others reading and liking your code by making
it easier to follow.
"""
@explanation [check: @moduledoc]
use Credo.Check, base_priority: :high
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
source_file.source
|> Credo.Code.to_tokens
|> collect_parenthetical_tokens([])
|> find_issues([], issue_meta)
end
defp collect_parenthetical_tokens([], acc), do: acc
defp collect_parenthetical_tokens([head | t], acc) do
acc =
case parenthetical_condition?(head, t) do
nil -> acc
false -> acc
token -> acc ++ [token]
end
collect_parenthetical_tokens(t, acc)
end
defp parenthetical_condition?({:"(", _} = token) do
{elem(token, 0), elem(token, 1), nil}
end
defp parenthetical_condition?(_), do: false
defp parenthetical_condition?({:identifier, _, :if}, [next_token | _t]) do
parenthetical_condition?(next_token)
end
defp parenthetical_condition?({:identifier, _, :unless}, [next_token | _t]) do
parenthetical_condition?(next_token)
end
defp parenthetical_condition?({:paren_identifier, _, :if} = token, _) do
token
end
defp parenthetical_condition?({:paren_identifier, _, :unless} = token, _) do
token
end
defp parenthetical_condition?(_, _), do: false
defp find_issues([], acc, _issue_meta) do
acc
end
defp find_issues([{_, {line_no, _, _}, trigger} | t], acc, issue_meta) do
new_issue = issue_for(issue_meta, line_no, trigger)
acc = acc ++ [new_issue]
find_issues(t, acc, issue_meta)
end
defp issue_for(issue_meta, line_no, trigger) do
format_issue issue_meta,
message: "The condition of `#{trigger}` should not be wrapped in parentheses.",
trigger: trigger,
line_no: line_no
end
end