Using `~p` dynamically inside a macro

Questions & Help Questions
, ,
5

Hmm, I think sigil_p/2 pattern matches against ast and unquoting that expression results in fully evaluated binary.

I bet there would be a more intuitive solution but this works:

defmodule A do
  defmacro __using__(opts) do
    path = opts[:path]

    quote do
      use Phoenix.Component

      def handle_event("event", _, socket) do
        path = sigil_p(unquote({:<<>>, _meta = [], ["/#{path}"]}), [])

        # ...
        {:noreply, socket}
      end
    end
  end
end

defmodule B do
  use A, path: "my-path"
end

warning: no route path for InformedCMSWeb.Router matches "/my-path"
  iex:112: B.handle_event/3

So I passed the simplified version of desired ast:

iex> quote(do: "/#{path}")
{:<<>>, [],
 [
   "/",
   {:"::", [],
    [
      {{:., [], [Kernel, :to_string]}, [], [{:path, [], Elixir}]},
      {:binary, [], Elixir}
    ]}
 ]}