You seem to be using agent here to simulate a mutable object. I don’t think that’s a good/idiomatic example for using agents (or processes for that matter).
It appears that traverse function here is used only to gather errors. You could write that in a pure functional way, by extracting a separate function which returns a list of errors. Maybe a function should be renamed to validate or something along those lines to express its main purpose.
Here’s a non-tested attempt:
defp validate([_|_] = data) do
data
|> Stream.map(&validate/1)
|> Enum.concat()
end
defp validate(%{"key" => name, "validate" => validation, "label" => label}) do
case validate_item(body |> Map.fetch!(name), label, validation) do
"" -> []
error -> [error]
end
end
defp validate(%{"components" => components}), do: validate(components)
defp validate(%{"columns" => columns}), do: validate(columns)
defp validate(%{"rows" => rows}), do: validate(rows)
defp validate(_other_kind_of_data), do: []
