fix: Trim triple newlines instead of double newlines

[Munksgaard]

Removing double newlines breaks formatting in e.g. the generated browser docs,
and breaks doctests, since they expect the example code sections to be separated
by the rest of the comments by double newlines.

Instead, we should focus on collapsing triple newlines, which can occur for
legitimate reasons, e.g. a section of the generated documentation doesn't return
any text, but which shouldn't be showed in the resulting documentation.

Fixes: #2433

I tried adding a regression test to code_interface_test.exs by adding the following, but it didn't work because Code.fetch_docs returned {:error, :module_not_found}:

  defmodule CalculationDocumentation do
    use Ash.Resource,
      data_layer: Ash.DataLayer.Ets,
      domain: Ash.Test.Domain

    attributes do
      attribute :foo, :string do
        public? true
      end
    end

    actions do
      defaults create: :*
    end

    calculations do
      calculate :foo_calculation, :boolean, expr(true) do
        description """
        Calculate a foo.

        This is hard to do.
        """
      end
    end

    code_interface do
      define_calculation :foo_calculation
    end
  end

  describe "documentation" do
    test "calculation code interface doc string doesn't strip double newlines" do
      generated_doc =
        Code.fetch_docs(CalculationDocumentation)
        |> dbg
        |> elem(6)
        |> Enum.find(&(elem(&1, 0) == {:function, :foo, 1}))
        |> elem(3)
        |> Map.fetch!("en")
        |> dbg

      assert String.contains?(generated_doc, """
             Calculate a foo.

             This is hard to do.
             """)
    end
  end

Any suggestions for a better way to test this would be greatly appreciated.

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Edit: Updated to reflect this comment: #2433 (comment)

[zachdaniel]

We can't remove this right now because AshPhoenix is using it. Also I see a formatting error, is that from these changes or in main? Either way, will merge once this is added back in 😄

[Munksgaard]

I got to the same realization when I went to sleep last night, sorry about that!

The formatting changes are caused by my changes, though there was also a formatting error in actions/destroy/bulk.ex which I've fixed in a separate commit.

[Munksgaard]

See also my comment in ash-project/ash_phoenix#439 (comment)

[Munksgaard]

Huh, the formatter in the CI behaves differently from my local install, with regards to that bulk destroy change. I'll remove that commit again.

[zachdaniel]

Thanks for pointing out the issues here! I'm just going to update the trim_double_newlines function to trim triple newlines. Its not a public function (@doc false) so it really doesn't matter how accurate the name is 😄

[zachdaniel]

This will then automatically resolve the issue in AshPhoenix as well 😄

[Munksgaard]

Thanks!