A diff-based solution to the problem of undoing the effects of formatting in the Igniter tool by the Ash team. Doesn't work for all the edge cases.

Igniter Diff.livemd

Igniter Diff

Mix.install([
  {:differ, "~> 0.1.1"}
])

UnFormat

defmodule UnFormat do
  def run(input, output) do
    input
    |> Differ.diff(output)
    |> Enum.flat_map(fn
      {op, str} ->
        cond do
          # Undo whitespace changes
          op == :del && str =~ ~r"^\s*$" ->
            [{:eq, str}]

          op == :ins && str =~ ~r"^\s*$" ->
            []

          # Undo opening parens changes
          op == :del && str =~ ~r"^[\s\(]*$" ->
            [{:eq, str}]

          op == :ins && str =~ ~r"^[\s\(]*$" ->
            []

          # Undo closing parens changes
          op == :del && str =~ ~r"^[\s\)]*$" ->
            [{:eq, str}]

          op == :ins && str =~ ~r"^[\s\)]*$" ->
            []

          true ->
            [{op, str}]
        end
    end)
    |> then(&Differ.patch!(input, &1))
  end
end

{:module, UnFormat, <<70, 79, 82, 49, 0, 0, 12, ...>>, {:run, 2}}

Whitespace Deleted

input =
  """
  config :fake,
            
            :buz,        (([:blat]))
    config :fake2, 1 + 1
  """

output =
  """
  config :fake, :buz, [:blat]
  config :fake2, (1 + 1)
  config :fake, foo: "baz"
  """

IO.puts(UnFormat.run(input, output))

config :fake,
          
          :buz,        (([:blat]))
  config :fake2, 1 + 1
config :fake, foo: "baz"

:ok

Whitespace Inserted

input =
  """
  config :fake, :buz, [1,2,3]
  """

output =
  """
  config :fake, :buz, [
    1,
    2,
    3]
  config :fake, foo: "baz"
  """

IO.puts(UnFormat.run(input, output))

config :fake, :buz, [1,2,3]
config :fake, foo: "baz"

:ok