trailing_white_space.ex

defmodule Credo.Check.Readability.TrailingWhiteSpace do
  use Credo.Check,
    base_priority: :low,
    tags: [:formatter],
    param_defaults: [
      ignore_strings: true
    ],
    explanations: [
      check: """
      There should be no white-space (i.e. tabs, spaces) at the end of a line.

      Most text editors provide a way to remove them automatically.
      """,
      params: [
        ignore_strings: "Set to `false` to check lines that are strings or in heredocs"
      ]
    ]

  alias Credo.Code
  alias Credo.Code.Strings
  alias Credo.Code.Heredocs

  @doc false
  @impl true
  def run(%SourceFile{} = source_file, params) do
    issue_meta = IssueMeta.for(source_file, params)
    ignore_strings = Params.get(params, :ignore_strings, __MODULE__)

    source_file
    |> to_lines(ignore_strings)
    |> traverse_line([], issue_meta)
  end

  defp to_lines(source_file, true) do
    source_file
    |> Strings.replace_with_spaces(".", ".")
    |> Heredocs.replace_with_spaces(".", ".", ".", source_file.filename)
    |> Code.to_lines()
  end

  defp to_lines(source_file, false) do
    SourceFile.lines(source_file)
  end

  defp traverse_line([{line_no, line} | tail], issues, issue_meta) do
    issues =
      case Regex.run(~r/\h+$/u, line, return: :index) do
        [{column, line_length}] ->
          [issue_for(issue_meta, line_no, column + 1, line_length) | issues]

        nil ->
          issues
      end

    traverse_line(tail, issues, issue_meta)
  end

  defp traverse_line([], issues, _issue_meta), do: issues

  defp issue_for(issue_meta, line_no, column, line_length) do
    format_issue(
      issue_meta,
      message: "There should be no trailing white-space at the end of a line.",
      line_no: line_no,
      column: column,
      trigger: String.duplicate(" ", line_length)
    )
  end
end