Add support for Sendgrid unique arguments

lib/bamboo/adapters/send_grid_adapter.ex

@@ -130,6 +130,7 @@ defmodule Bamboo.SendGridAdapter do
     |> put_bypass_list_management(email)
     |> put_google_analytics(email)
     |> put_ip_pool_name(email)
+    |> put_unique_args(email)
   end
 
   defp put_from(body, %Email{from: from}) do
@@ -440,4 +441,12 @@ defmodule Bamboo.SendGridAdapter do
     do: Map.put(body, :ip_pool_name, ip_pool_name)
 
   defp put_ip_pool_name(body, _), do: body
+
+  defp put_unique_args(body, %Email{private: %{unique_args: unique_args}})
+       when is_map(unique_args) do
+    body
+    |> Map.put(:unique_args, unique_args)
+  end
+
+  defp put_unique_args(body, _), do: body
 end

lib/bamboo/adapters/send_grid_helper.ex

@@ -22,6 +22,7 @@ defmodule Bamboo.SendGridHelper do
   @allowed_google_analytics_utm_params ~w(utm_source utm_medium utm_campaign utm_term utm_content)a
   @send_at_field :sendgrid_send_at
   @ip_pool_name_field :ip_pool_name
+  @unique_args :unique_args
 
   @doc """
   Specify the template for SendGrid to use for the context of the substitution
@@ -294,4 +295,25 @@ defmodule Bamboo.SendGridHelper do
     email
     |> Email.put_private(@ip_pool_name_field, ip_pool_name)
   end
+
+  @doc """
+  A map of unique arguments for this email. This will override any existing unique arguments.
+
+  ## Example
+
+      email
+      |> with_unique_args(%{new_arg_1: "new arg 1", new_arg_2: "new arg 2"})
+  """
+  def with_unique_args(email, unique_args) when is_map(unique_args) do
+    unique_args =
+      Map.get(email.private, @unique_args, %{})
+      |> Map.merge(unique_args)
+
+    email
+    |> Email.put_private(@unique_args, unique_args)
+  end
+
+  def with_unique_args(_email, _unique_args) do
+    raise "expected a map of unique arguments"
+  end
 end

test/lib/bamboo/adapters/send_grid_adapter_test.exs

@@ -628,6 +628,25 @@ defmodule Bamboo.SendGridAdapterTest do
     assert msg =~ ~r/'email' field/
   end
 
+  test "deliver/2 correctly handles with_unique_args" do
+    email = new_email()
+
+    unique_args = %{
+      new_arg1: "new arg 1",
+      new_arg2: "new arg 2",
+      new_arg3: "new arg 3"
+    }
+
+    email
+    |> Bamboo.SendGridHelper.with_unique_args(unique_args)
+    |> SendGridAdapter.deliver(@config)
+
+    assert_receive {:fake_sendgrid, %{params: params}}
+    assert params["unique_args"]["new_arg1"] == "new arg 1"
+    assert params["unique_args"]["new_arg2"] == "new arg 2"
+    assert params["unique_args"]["new_arg3"] == "new arg 3"
+  end
+
   test "deliver/2 will set sandbox mode correctly" do
     email = new_email()
     email |> SendGridAdapter.deliver(@config_with_sandbox_enabled)

test/lib/bamboo/adapters/send_grid_helper_test.exs

@@ -207,4 +207,28 @@ defmodule Bamboo.SendGridHelperTest do
     email = email |> with_ip_pool_name(@ip_pool_name)
     assert email.private[:ip_pool_name] == @ip_pool_name
   end
+
+  test "with_unique_args/2 merges multiple maps", %{email: email} do
+    email =
+      email
+      |> with_unique_args(%{new_arg_1: "new arg 1", new_arg_2: "new arg 2"})
+      |> with_unique_args(%{new_arg_3: "new arg 3"})
+
+    assert map_size(email.private[:unique_args]) == 3
+  end
+
+  test "with_unique_args/2 overrides duplicate entries", %{email: email} do
+    email =
+      email
+      |> with_unique_args(%{new_arg_1: "new arg 1"})
+      |> with_unique_args(%{new_arg_1: "latest new arg 1", new_arg_2: "new arg 2"})
+
+    assert map_size(email.private[:unique_args]) == 2
+  end
+
+  test "with_unique_args/2 raises on non-map parameter", %{email: email} do
+    assert_raise RuntimeError, fn ->
+      email |> with_unique_args(["new arg"])
+    end
+  end
 end