Four approaches to expressing nested logic

four_approaches.ex

defmodule Sample do
  #
  # VERSION 1
  # The naive approach: just nest the if/else statements. Pretty readable.
  #
  
  def custom_block(project, label) do
    # ... validations ...
    if project do
      if block = Enum.find(project.custom_blocks, & &1.label == label) do
        raw block.body
      else
        default_block(label)
      end
    else
      default_block(label)
    end
  end

  #
  # VERSION 2
  # I think this is what "with" statements are for, let's try that. Feels clunky and redundant though.
  #

  def custom_block(project, label) do
    # ... validations ...
    with true <- project != nil,
         block <- Enum.find(project.custom_blocks, & &1.label == label),
         true <- block != nil do
      raw block.body
    else
      default_block(label)
    end
  end

  #
  # VERSION 3
  # Pattern-matching to reduce the verbosity of the "with" statement. Still feels weird.
  #

  def custom_block(project, label) do
    # ... validations ...
    with %Project{} <- project,
         %CustomBlock{} = block <- Enum.find(project.custom_blocks, & &1.label == label) do
      raw block.body
    else
      default_block(label)
    end
  end

  #
  # VERSION 4
  # Helper function with 2 signatures lets me get rid of the nestedness in the main function. Psew.
  #

  def custom_block(project, label) do
    # ... validations ...
    if block = find_block(project, label) do
      raw block.body
    else
      default_block(label)
    end
  end

  defp find_block(nil, label), do: nil
  defp find_block(proj, label), do: Enum.find(proj.custom_blocks, & &1.label == label)
end