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A static code analysis tool with a focus on code consistency and teaching.
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Files
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, elixir_version: ">= 1.3.2"
@doc false
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
min_number = Params.get(params, :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} = location, number} | t], acc, issue_meta) do
source = source_fragment(location, issue_meta)
underscored_number = number_with_underscores(number, source)
new_issue =
if decimal_in_source?(source) && source != underscored_number do
[issue_for(
issue_meta, line_no, column1, source, underscored_number
)]
else
[]
end
acc = acc ++ new_issue
find_issues(t, acc, issue_meta)
end
defp number_with_underscores(number, _) when is_integer(number) do
number
|> to_string
|> add_underscores_to_number_string
end
defp number_with_underscores(number, source_fragment) when is_number(number) do
case String.split(source_fragment, ".", parts: 2) do
[num, decimal] ->
Enum.join([add_underscores_to_number_string(num), decimal], ".")
[num] ->
add_underscores_to_number_string(num)
end
end
defp add_underscores_to_number_string(string) do
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
defp decimal_in_source?(source) do
case String.slice(source, 0, 2) do
"0b" -> false
"0o" -> false
"0x" -> false
_ -> true
end
end
defp source_fragment({line_no, column1, column2} = tuple, issue_meta) do
fragment =
issue_meta
|> IssueMeta.source_file
|> SourceFile.line_at(line_no)
|> String.slice((column1 - 1)..(column2 - 1))
|> String.strip
|> String.replace(~r/\D$/, "")
if Version.match?(System.version, "< 1.3.2-dev") do
source_fragment_pre_132(tuple, issue_meta, fragment)
else
fragment
end
end
# There's a bug in the :elixir_tokenizer.tokenize/3 in versions prior to
# 1.3.2 where the _ in the source code is not included in the token's
# length, so that means we have to re-calculate the token if it has _ in it.
#
# Unfortuately this leaves the line and column counts out of sync so this
# "fix" only works "reliably" for the first number with _ in the line.
defp source_fragment_pre_132({line_no, column1, column2}, issue_meta, first_fragment) do
underscores = (first_fragment |> String.split("_") |> Enum.count) - 1
if underscores > 0 do
issue_meta
|> IssueMeta.source_file
|> SourceFile.line_at(line_no)
|> String.slice((column1 - 1)..(column2 - 2 + underscores))
|> String.strip
|> String.replace(~r/\D$/, "")
else
first_fragment
end
end
end