Raise if all recipients are nil

See comment:
#40 (comment)

lib/bamboo.ex

@@ -16,5 +16,18 @@ defmodule Bamboo do
     end
   end
 
+  defmodule NilRecipientsError do
+    defexception [:message]
+
+    def exception(email) do
+      message = """
+      All recipients were set to nil. Must specify at least one recipient.
+
+      Full email - #{inspect email, limit: :infinity}
+      """
+      %NilRecipientsError{message: message}
+    end
+  end
+
   def start(_type, _args), do: Bamboo.SentEmail.start_link
 end

lib/bamboo/mailer.ex

@@ -72,15 +72,18 @@ defmodule Bamboo.Mailer do
 
   @doc false
   def deliver(adapter, email, config) do
-    email = email |> Bamboo.Mailer.normalize_addresses
+    email = email |> validate_and_normalize
 
-    debug(email)
-    adapter.deliver(email, config)
+    unless email.to == [] && email.cc == [] && email.bcc == [] do
+      debug(email)
+      adapter.deliver(email, config)
+    end
+    email
   end
 
   @doc false
   def deliver_later(adapter, email, config) do
-    email = email |> Bamboo.Mailer.normalize_addresses
+    email = email |> validate_and_normalize
 
     debug(email)
     adapter.deliver_later(email, config)
@@ -94,6 +97,18 @@ defmodule Bamboo.Mailer do
     """
   end
 
+  defp validate_and_normalize(email) do
+    email |> validate_recipients |> normalize_addresses
+  end
+
+  defp validate_recipients(email) do
+    if email.to == nil && email.cc == nil && email.bcc == nil do
+      raise Bamboo.NilRecipientsError, email
+    else
+      email
+    end
+  end
+
   @doc """
   Wraps to, cc and bcc addresses in a list and normalizes email addresses.
 

test/lib/bamboo/local_adapter_test.exs

@@ -42,7 +42,7 @@ defmodule Bamboo.LocalAdapterTest do
   end
 
   defp new_normalized_email(attrs) do
-    attrs = attrs |> Keyword.put(:from, "foo@bar.com")
+    attrs = Keyword.merge([from: "foo@bar.com", to: "foo@bar.com"], attrs)
     new_email(attrs) |> Bamboo.Mailer.normalize_addresses
   end
 end

test/lib/bamboo/mailer_test.exs

@@ -28,8 +28,11 @@ defmodule Bamboo.MailerTest do
   end
 
   test "deliver/1 calls the adapter with the email and config" do
-    FooMailer.deliver(new_email)
+    email = new_email(to: "foo@bar.com")
 
+    returned_email = FooMailer.deliver(email)
+
+    assert returned_email == email
     assert_received {:deliver, %Bamboo.Email{}, @mailer_config}
   end
 
@@ -41,6 +44,34 @@ defmodule Bamboo.MailerTest do
     end
   end
 
+  test "deliver/1 with empty lists for recipients does not deliver email" do
+    new_email(to: [], cc: [], bcc: []) |> FooMailer.deliver(nil_recipients: :allowed)
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: [], cc: nil, bcc: nil) |> FooMailer.deliver
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: nil, cc: [], bcc: nil) |> FooMailer.deliver
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: nil, cc: nil, bcc: []) |> FooMailer.deliver
+    refute_received {:deliver, _, @mailer_config}
+  end
+
+  test "deliver_later/1 with empty lists for recipients does not deliver email" do
+    new_email(to: [], cc: [], bcc: []) |> FooMailer.deliver_later
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: [], cc: nil, bcc: nil) |> FooMailer.deliver_later
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: nil, cc: [], bcc: nil) |> FooMailer.deliver_later
+    refute_received {:deliver, _, @mailer_config}
+
+    new_email(to: nil, cc: nil, bcc: []) |> FooMailer.deliver_later
+    refute_received {:deliver, _, @mailer_config}
+  end
+
   test "deliver_later/1 calls deliver_later on the adapter" do
     email = new_email
 
@@ -102,7 +133,13 @@ defmodule Bamboo.MailerTest do
     end
   end
 
-  test "raises an error if a map is passed in an not a Bamboo.EmailAddress" do
+  test "raises if all receipients are nil" do
+    assert_raise Bamboo.NilRecipientsError, fn ->
+      new_email(to: nil, cc: nil, bcc: nil) |> FooMailer.deliver
+    end
+  end
+
+  test "raises if a map is passed in instead of a Bamboo.EmailAddress" do
     email = new_email(from: %{foo: :bar})
 
     assert_raise ArgumentError, fn ->
@@ -111,7 +148,7 @@ defmodule Bamboo.MailerTest do
   end
 
   defp new_email(attrs \\ []) do
-    attrs = Keyword.merge([from: "foo@bar.com"], attrs)
+    attrs = Keyword.merge([from: "foo@bar.com", to: "foo@bar.com"], attrs)
     Email.new_email(attrs)
   end
 end

test/lib/bamboo/mandrill_adapter_test.exs

@@ -150,7 +150,7 @@ defmodule Bamboo.MandrillAdapterTest do
   end
 
   defp new_email(attrs \\ []) do
-    attrs = Keyword.merge([from: "foo@bar.com"], attrs)
+    attrs = Keyword.merge([from: "foo@bar.com", to: []], attrs)
     Email.new_email(attrs)
   end
 end

test/lib/bamboo/test_adapter_test.exs

@@ -54,7 +54,7 @@ defmodule Bamboo.TestAdapterTest do
   end
 
   defp new_normalized_email(attrs \\ []) do
-    [from: "foo@bar.com"]
+    [from: "foo@bar.com", to: ["foo@bar.com"]]
     |> Keyword.merge(attrs)
     |> new_email
     |> Bamboo.Mailer.normalize_addresses