Update Mailgun.deliver to return ok/error tuples (#573)

What changed?
==============

Updates Mailgin.deliver function to return ok/error tuples to abide by
the new api.

Note on raising configuration errors
-----------------------------------

We do not change the raising of errors when they deal with configuration
options. Those errors are categorically different. We want to return
ok/error tuples when there's an error building/delivering email. If
a user of Bamboo is missing a configuration variable, it seems important
to raise an error.

lib/bamboo/adapters/mailgun_adapter.ex

@@ -104,13 +104,13 @@ defmodule Bamboo.MailgunAdapter do
          ) do
       {:ok, status, _headers, response} when status > 299 ->
         body = decode_body(body)
-        raise_api_error(@service_name, response, body)
+        {:error, build_api_error(@service_name, response, body)}
 
       {:ok, status, headers, response} ->
-        %{status_code: status, headers: headers, body: response}
+        {:ok, %{status_code: status, headers: headers, body: response}}
 
       {:error, reason} ->
-        raise_api_error(inspect(reason))
+        {:error, build_api_error(inspect(reason))}
     end
   end
 

test/lib/bamboo/adapters/mailgun_adapter_test.exs

@@ -162,6 +162,12 @@ defmodule Bamboo.MailgunAdapterTest do
     assert request_path == "/test.tt/messages"
   end
 
+  test "deliver/2 returns an {:ok, response} tuple" do
+    {:ok, response} = new_email() |> MailgunAdapter.deliver(@config)
+
+    assert %{status_code: 200, headers: _, body: _} = response
+  end
+
   test "deliver/2 sends from, subject, text body, html body, headers, custom vars and recipient variables" do
     email =
       new_email(
@@ -293,28 +299,24 @@ defmodule Bamboo.MailgunAdapterTest do
     assert params["t:text"] == "yes"
   end
 
-  test "raises if the response is not a success" do
+  test "returns an error if the response is not a success" do
     email = new_email(from: "INVALID_EMAIL")
 
-    assert_raise Bamboo.ApiError,
-                 ~r/.*%{.*\"from\" => \"INVALID_EMAIL\".*}/,
-                 fn ->
-                   email |> MailgunAdapter.deliver(@config)
-                 end
+    {:error, %Bamboo.ApiError{} = error} = email |> MailgunAdapter.deliver(@config)
+
+    assert error.message =~ ~r/.*%{.*\"from\" => \"INVALID_EMAIL\".*}/
   end
 
-  test "raises if the response is not a success with attachment" do
+  test "returns an error if the response is not a success with attachment" do
     attachment_source_path = Path.join(__DIR__, "../../../support/attachment.txt")
 
     email =
       new_email(from: "INVALID_EMAIL")
       |> Email.put_attachment(attachment_source_path)
 
-    assert_raise Bamboo.ApiError,
-                 ~r/.*{.*\"from\", \"INVALID_EMAIL\".*}/,
-                 fn ->
-                   email |> MailgunAdapter.deliver(@config)
-                 end
+    {:error, %Bamboo.ApiError{} = error} = email |> MailgunAdapter.deliver(@config)
+
+    assert error.message =~ ~r/.*{.*\"from\", \"INVALID_EMAIL\".*}/
   end
 
   defp new_email(attrs \\ []) do