defmodule Credo.Check.Readability.LargeNumbers do
use Credo.Check,
id: "EX3006",
base_priority: :high,
tags: [:formatter],
param_defaults: [
only_greater_than: 9_999,
trailing_digits: []
],
explanations: [
check: """
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.
""",
params: [
only_greater_than: "The check only reports numbers greater than this.",
trailing_digits:
"The check allows for the given number of trailing digits (can be a number, range or list)"
]
]
@doc false
def run(%SourceFile{} = source_file, params) do
min_number = Params.get(params, :only_greater_than, __MODULE__)
issue_meta = IssueMeta.for(source_file, Keyword.merge(params, only_greater_than: min_number))
allowed_trailing_digits =
case Params.get(params, :trailing_digits, __MODULE__) do
%Range{} = value -> Enum.to_list(value)
value -> List.wrap(value)
end
source_file
|> Credo.Code.to_tokens()
|> collect_number_tokens([], min_number)
|> find_issues([], allowed_trailing_digits, 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
token -> acc ++ [token]
end
collect_number_tokens(t, acc, min_number)
end
# tuple for Elixir >= 1.10.0
defp number_token({:flt, {_, _, number}, _} = tuple, min_number) when min_number < number do
tuple
end
# tuple for Elixir >= 1.6.0
defp number_token({:int, {_, _, number}, _} = tuple, min_number) when min_number < number do
tuple
end
defp number_token({:float, {_, _, number}, _} = tuple, min_number) when min_number < number do
tuple
end
# tuple for Elixir <= 1.5.x
defp number_token({:number, _, number} = tuple, min_number) when min_number < number do
tuple
end
defp number_token(_, _), do: nil
defp find_issues([], acc, _allowed_trailing_digits, _issue_meta) do
acc
end
# tuple for Elixir >= 1.10.0
defp find_issues(
[{:flt, {line_no, column1, number} = location, _} | t],
acc,
allowed_trailing_digits,
issue_meta
) do
acc =
acc ++ find_issue(line_no, column1, location, number, allowed_trailing_digits, issue_meta)
find_issues(t, acc, allowed_trailing_digits, issue_meta)
end
# tuple for Elixir >= 1.6.0
defp find_issues(
[{:int, {line_no, column1, number} = location, _} | t],
acc,
allowed_trailing_digits,
issue_meta
) do
acc =
acc ++ find_issue(line_no, column1, location, number, allowed_trailing_digits, issue_meta)
find_issues(t, acc, allowed_trailing_digits, issue_meta)
end
defp find_issues(
[{:float, {line_no, column1, number} = location, _} | t],
acc,
allowed_trailing_digits,
issue_meta
) do
acc =
acc ++ find_issue(line_no, column1, location, number, allowed_trailing_digits, issue_meta)
find_issues(t, acc, allowed_trailing_digits, issue_meta)
end
# tuple for Elixir <= 1.5.x
defp find_issues(
[{:number, {line_no, column1, _column2} = location, number} | t],
acc,
allowed_trailing_digits,
issue_meta
) do
acc =
acc ++ find_issue(line_no, column1, location, number, allowed_trailing_digits, issue_meta)
find_issues(t, acc, allowed_trailing_digits, issue_meta)
end
defp find_issue(line_no, column1, location, number, allowed_trailing_digits, issue_meta) do
source = source_fragment(location, issue_meta)
underscored_versions = number_with_underscores(number, allowed_trailing_digits, source)
if decimal_in_source?(source) && not Enum.member?(underscored_versions, source) do
[
issue_for(
issue_meta,
line_no,
column1,
source,
underscored_versions
)
]
else
[]
end
end
defp number_with_underscores(number, allowed_trailing_digits, _) when is_integer(number) do
number
|> to_string
|> add_underscores_to_number_string(allowed_trailing_digits)
end
defp number_with_underscores(number, allowed_trailing_digits, source_fragment)
when is_number(number) do
case String.split(source_fragment, ".", parts: 2) do
[num, decimal] ->
add_underscores_to_number_string(num, allowed_trailing_digits)
|> Enum.map(fn base -> Enum.join([base, decimal], ".") end)
[num] ->
add_underscores_to_number_string(num, allowed_trailing_digits)
end
end
defp add_underscores_to_number_string(string, allowed_trailing_digits) do
without_trailing_digits =
string
|> String.reverse()
|> String.replace(~r/(\d{3})(?=\d)/, "\\1_")
|> String.reverse()
all_trailing_digit_versions =
Enum.map(allowed_trailing_digits, fn trailing_digits ->
if String.length(string) > trailing_digits do
base =
String.slice(string, 0..(-1 * trailing_digits - 1)//1)
|> String.reverse()
|> String.replace(~r/(\d{3})(?=\d)/, "\\1_")
|> String.reverse()
trailing = String.slice(string, (-1 * trailing_digits)..-1//1)
"#{base}_#{trailing}"
end
end)
([without_trailing_digits] ++ all_trailing_digit_versions)
|> Enum.reject(&is_nil/1)
|> Enum.uniq()
end
defp issue_for(issue_meta, line_no, column, trigger, expected) do
params = IssueMeta.params(issue_meta)
only_greater_than = Params.get(params, :only_greater_than, __MODULE__)
format_issue(
issue_meta,
message:
"Numbers larger than #{only_greater_than} should be written with underscores: #{Enum.join(expected, " or ")}",
line_no: line_no,
column: column,
trigger: trigger
)
end
defp decimal_in_source?(source) do
case String.slice(source, 0, 2) do
"0b" -> false
"0o" -> false
"0x" -> false
"" -> false
_ -> true
end
end
defp source_fragment({line_no, column1, _}, issue_meta) do
line =
issue_meta
|> IssueMeta.source_file()
|> SourceFile.line_at(line_no)
beginning_of_number =
~r/[^0-9_oxb]*([0-9_oxb]+$)/
|> Regex.run(String.slice(line, 1..column1))
|> List.wrap()
|> List.last()
|> to_string()
ending_of_number =
~r/^([0-9_\.]+)/
|> Regex.run(String.slice(line, (column1 + 1)..-1//1))
|> List.wrap()
|> List.last()
|> to_string()
|> String.replace(~r/\.\..*/, "")
beginning_of_number <> ending_of_number
end
end
