Fix Noticed::DeliveryMethods::Email to support keyword arguments

docs/delivery_methods/email.md

@@ -15,6 +15,21 @@ deliver_by :email do |config|
 end
 ```
 
+Mailer methods with keyword arguments are also supported.
+
+```ruby
+deliver_by :email do |config|
+  config.mailer = "UserMailer"
+  config.method = :greeting
+  config.params = ->{ params }
+  config.kwargs = ->{ {body: "Hey there", subject: "Thanks for joining"} }
+
+  # Enqueues a separate job for sending the email using deliver_later.
+  # Deliveries already happen in jobs so this is typically unnecessary.
+  # config.enqueue = false
+end
+```
+
 ##### Options
 
 - `mailer` - **Required**
@@ -30,6 +45,12 @@ end
   Use a custom method to define the params sent to the mailer. `recipient` will be merged into the params.
 
 - `args` - _Optional_
+
+  The arguments for the `method` if it uses **positional arguments** (eg: `def hello(a, b, c=1)`)
+
+- `kwargs` - _Optional_
+
+  The arguments for the `method` if it uses **keyword arguments** (eg: `def hello(a:, b:, c: 1)`)
 
 - `enqueue: false` - _Optional_
 

lib/noticed/delivery_methods/email.rb

@@ -7,7 +7,20 @@ def deliver
         mailer = fetch_constant(:mailer)
         email = evaluate_option(:method)
         args = evaluate_option(:args) || []
-        mail = mailer.with(params).public_send(email, *args)
+        kwargs = evaluate_option(:kwargs) || {}
+
+        if args.present? && kwargs.present?
+          raise ArgumentError, "`args` and `kwargs` cannot both be provided."
+        end
+
+        mailer_instance = mailer.with(params)
+
+        mail = if kwargs.present?
+          mailer_instance.public_send(email, **kwargs)
+        else
+          mailer_instance.public_send(email, *args)
+        end
+
         (!!evaluate_option(:enqueue)) ? mail.deliver_later : mail.deliver_now
       end
 

test/delivery_methods/email_test.rb

@@ -8,7 +8,7 @@ class EmailTest < ActiveSupport::TestCase
     @notification = noticed_notifications(:one)
   end
 
-  test "sends email" do
+  test "sends email (with args)" do
     set_config(
       mailer: "UserMailer",
       method: "new_comment",
@@ -21,6 +21,78 @@ class EmailTest < ActiveSupport::TestCase
     end
   end
 
+  test "sends email (with kwargs)" do
+    set_config(
+      mailer: "UserMailer",
+      method: "greeting",
+      params: -> { {foo: :bar} },
+      kwargs: -> { {body: "Custom"} }
+    )
+
+    assert_emails(1) do
+      @delivery_method.deliver
+    end
+  end
+
+  test "sends email (with kwargs, replacing default argument)" do
+    set_config(
+      mailer: "UserMailer",
+      method: "greeting",
+      params: -> { {foo: :bar} },
+      kwargs: -> { {body: "Custom", subject: "Testing"} }
+    )
+
+    assert_emails(1) do
+      @delivery_method.deliver
+    end
+  end
+
+  test "raises the underlying ArgumentError if kwargs are missing" do
+    set_config(
+      mailer: "UserMailer",
+      method: "greeting",
+      params: -> { {foo: :bar} },
+      kwargs: -> { {baz: 123} }
+    )
+
+    error = assert_raises ArgumentError do
+      @delivery_method.deliver
+    end
+
+    assert_equal "missing keyword: :body", error.message
+  end
+
+  test "raises the underlying ArgumentError if unknown kwargs are given" do
+    set_config(
+      mailer: "UserMailer",
+      method: "greeting",
+      params: -> { {foo: :bar} },
+      kwargs: -> { {body: "Test", baz: 123} }
+    )
+
+    error = assert_raises ArgumentError do
+      @delivery_method.deliver
+    end
+
+    assert_equal "unknown keyword: :baz", error.message
+  end
+
+  test "raises an ArgumentError if both args and kwargs are present, since only one can be used" do
+    set_config(
+      mailer: "UserMailer",
+      method: "greeting",
+      params: -> { {foo: :bar} },
+      args: -> { ["hey"] },
+      kwargs: -> { {body: "Test"} }
+    )
+
+    error = assert_raises ArgumentError do
+      @delivery_method.deliver
+    end
+
+    assert_equal "`args` and `kwargs` cannot both be provided.", error.message
+  end
+
   test "enqueues email" do
     set_config(
       mailer: "UserMailer",

test/dummy/app/mailers/user_mailer.rb

@@ -3,6 +3,10 @@ def new_comment(*args)
     mail(body: "new comment")
   end
 
+  def greeting(body:, subject: "Hello")
+    mail(body: body, subject: subject)
+  end
+
   def receipt
     mail(body: "receipt")
   end