Add support for SendGrid's asm_group_id

lib/bamboo/adapters/send_grid_adapter.ex

@@ -103,6 +103,7 @@ defmodule Bamboo.SendGridAdapter do
     |> put_template_id(email)
     |> put_attachments(email)
     |> put_categories(email)
+    |> put_asm_group_id(email)
     |> put_settings(config)
   end
 
@@ -215,6 +216,12 @@ defmodule Bamboo.SendGridAdapter do
 
   defp put_categories(body, _), do: body
 
+  defp put_asm_group_id(body, %Email{private: %{asm_group_id: asm_group_id}}) when is_integer(asm_group_id) do
+    body
+    |> Map.put(:asm, %{group_id: asm_group_id})
+  end
+  defp put_asm_group_id(body, _), do: body
+
   defp put_attachments(body, %Email{attachments: []}), do: body
 
   defp put_attachments(body, %Email{attachments: attachments}) do

lib/bamboo/adapters/send_grid_helper.ex

@@ -15,6 +15,7 @@ defmodule Bamboo.SendGridHelper do
   @id_size 36
   @field_name :send_grid_template
   @categories :categories
+  @asm_group_id :asm_group_id
 
   @doc """
   Specify the template for SendGrid to use for the context of the substitution
@@ -83,6 +84,23 @@ defmodule Bamboo.SendGridHelper do
     raise "expected a list of category strings"
   end
 
+  @doc """
+  An integer id for an ASM (Advanced Suppression Manager) group that this email should belong to.
+  This can be used to let receipients unsubscribe from only a certain type of communication.
+
+  ## Example
+
+      email
+      |> with_asm_group_id(1234)
+  """
+  def with_asm_group_id(email, asm_group_id) when is_integer(asm_group_id) do
+    email
+    |> Email.put_private(@asm_group_id, asm_group_id)
+  end
+  def with_asm_group_id(_email, asm_group_id) do
+    raise "expected the asm_group_id parameter to be an integer, got #{asm_group_id}"
+  end
+
   defp set_template(template, template_id) do
     template
     |> Map.merge(%{template_id: template_id})

test/lib/bamboo/adapters/send_grid_adapter_test.exs

@@ -198,6 +198,20 @@ defmodule Bamboo.SendGridAdapterTest do
     assert personalization["substitutions"] == %{"%foo%" => "bar"}
   end
 
+  test "deliver/2 correctly handles an asm_group_id" do
+    email = new_email(
+      from: {"From", "from@foo.com"},
+      subject: "My Subject",
+    )
+
+    email
+    |> Bamboo.SendGridHelper.with_asm_group_id(1234)
+    |> SendGridAdapter.deliver(@config)
+
+    assert_receive {:fake_sendgrid, %{params: params}}
+    assert params["asm"]["group_id"] == 1234
+  end
+
   test "deliver/2 doesn't force a subject" do
     email = new_email(from: {"From", "from@foo.com"})
 

test/lib/bamboo/adapters/sendgrid_helper_test.exs

@@ -100,4 +100,15 @@ defmodule Bamboo.SendGridHelperTest do
 
     assert length(email.private[:categories]) == 10
   end
+
+  test "with_asm_group_id/2 adds the correct property", %{email: email} do
+    email = email |> with_asm_group_id(1234)
+    assert email.private[:asm_group_id] == 1234
+  end
+
+  test "with_asm_group_id/2 raises on non-integer id", %{email: email} do
+    assert_raise RuntimeError, fn ->
+      email |> with_asm_group_id("1234")
+    end
+  end
 end