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lib/credo/check/readability/large_numbers.ex

defmodule Credo.Check.Readability.LargeNumbers do
@moduledoc """
Numbers can contain underscores for readability purposes.
These do not affect the value of the number, but can help read large numbers
more easily.
141592654 # how large is this number?
141_592_654 # ah, it's in the hundreds of millions!
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,
params: [
only_greater_than: "The check only reports numbers greater than this.",
]
]
@default_params [
only_greater_than: 9_999,
]
use Credo.Check, base_priority: :high
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
min_number = params |> Params.get(:only_greater_than, @default_params)
source_file.source
|> Credo.Code.to_tokens
|> collect_number_tokens([], min_number)
|> find_issues([], issue_meta)
end
defp collect_number_tokens([], acc, _), do: acc
defp collect_number_tokens([head | t], acc, min_number) do
acc =
case number_token(head, min_number) do
nil -> acc
false -> acc
token -> acc ++ [token]
end
collect_number_tokens(t, acc, min_number)
end
defp number_token({:number, _, number} = tuple, min_number) when min_number < number do
tuple
end
defp number_token(_, _), do: nil
defp find_issues([], acc, _issue_meta) do
acc
end
defp find_issues([{:number, {line_no, column1, _column2}, number} | t], acc, issue_meta) do
line =
issue_meta
|> IssueMeta.source_file
|> SourceFile.line_at(line_no)
line_ending = String.slice(line, 0..column1 - 1)
underscore_count =
~r/\d_\d/
|> Regex.run(line_ending)
|> List.wrap
|> Enum.count
temp_string =
line
|> String.slice(column1 - 1 + underscore_count..-1)
found_string =
~r/([0-9\_]*\.[0-9]+|[0-9\_]+)/
|> Regex.run(temp_string)
|> List.first
underscored_number = number_with_underscores(number)
new_issue =
if found_string != underscored_number do
[issue_for(
issue_meta, line_no, column1, found_string, underscored_number
)]
else
[]
end
acc = acc ++ new_issue
find_issues(t, acc, issue_meta)
end
defp number_with_underscores(number) do
number
|> to_string
|> String.reverse
|> String.replace(~r/(\d{3})(?=\d)/, "\\1_")
|> String.reverse
end
def issue_for(issue_meta, line_no, column, trigger, expected) do
format_issue issue_meta,
message: "Large numbers should be written with underscores: #{expected}",
line_no: line_no,
column: column,
trigger: trigger
end
end