When reading this I expected something different …

It would be nice if you could provide a API which looks like:

xml = """
xml code goes here …
"""

MyLib.parse(xml, "some selector", mapper_module, nested: true)

mapper_module should be a module which implements specific behaviour which let’s say implements such set of functions: struct_mapper/1, content_mapper/2 and cast_func/3.

struct_mapper should be a function which determines module name based on tag, for example:

defmodule Example do
  def struct_mapper("tag-name"), do: ModuleName
end

content_mapper should be a function which determines where specific tag should be added to struct

defmodule Example do
  def content_mapper(MyModule, "content-tag"), do: :content
end

cast_func should be a function like changeset function used in ecto-based projects, for example:

defmodule Example do
  def cast_func(struct, attributes_map, content_map) do
    params = Map.merge(attributes_map, content_map)
    struct |> struct.__struct__.changeset(params) |> do_cast_func()
  end

  defp do_cast_func(%{valid: true} = changeset) do
    {:ok, Changeset.apply_changes(changeset)
  end

  defp do_cast_func(changeset), do: {:error, changeset}
end

Those examples instead of generic predefined structs would allow to nicely cast any XML data into current application structs which would simplify business logic much.

Please notice that with slight changes to mapper_module (I provided just a simple example) you should be able to write a default mapper_module to match your actual predefined structs. That solution would be easier for smaller scripts which does not defines ecto schemas or similar stuff.

What do you think about it?