Only attach the attachments when there's attachments to attach. (#21)

* Only attach the attachments when there's attachments to attach. Fixes #20

* Fixing compilation error. Ensure we can build the email without attachments

spec/carbon_sendgrid_adapter_spec.cr

@@ -156,7 +156,7 @@ describe Carbon::SendGridAdapter do
     end
 
     it "handles attachments" do
-      email = FakeEmail.new(text_body: "0")
+      email = FakeEmailWithAttachments.new(text_body: "0")
       params = Carbon::SendGridAdapter::Email.new(email, api_key: "fake_key").params
       attachments = params["attachments"].as(Array)
       attachments.size.should eq(1)

spec/support/fake_email.cr

@@ -18,13 +18,4 @@ class FakeEmail < Carbon::Email
   cc @cc
   bcc @bcc
   subject @subject
-  attachment contract
-
-  def contract
-    {
-      io:        IO::Memory.new("Sign here"),
-      file_name: "contract.pdf",
-      mime_type: "application/pdf",
-    }
-  end
 end

spec/support/fake_email_with_attachments.cr

@@ -0,0 +1,30 @@
+class FakeEmailWithAttachments < Carbon::Email
+  getter text_body, html_body
+
+  def initialize(
+    @from = Carbon::Address.new("from@example.com"),
+    @to = [] of Carbon::Address,
+    @cc = [] of Carbon::Address,
+    @bcc = [] of Carbon::Address,
+    @headers = {} of String => String,
+    @subject = "subject",
+    @text_body : String? = nil,
+    @html_body : String? = nil
+  )
+  end
+
+  from @from
+  to @to
+  cc @cc
+  bcc @bcc
+  subject @subject
+  attachment contract
+
+  def contract
+    {
+      io:        IO::Memory.new("Sign here"),
+      file_name: "contract.pdf",
+      mime_type: "application/pdf",
+    }
+  end
+end

src/carbon_sendgrid_adapter.cr

@@ -48,6 +48,11 @@ class Carbon::SendGridAdapter < Carbon::Adapter
         "attachments"      => attachments,
       }.compact
 
+      # If Sendgrid sees an empty attachments array, it'll return an error
+      if data["attachments"].empty?
+        data.delete("attachments")
+      end
+
       if asm_data = email.asm
         data = data.merge!({"asm" => asm_data})
       else
@@ -141,7 +146,7 @@ class Carbon::SendGridAdapter < Carbon::Adapter
 
     private def attachments : Array(Hash(String, String))
       files = [] of Hash(String, String)
-      email.attachments.map do |attachment|
+      email.attachments.each do |attachment|
         case attachment
         in AttachFile, ResourceFile
           files.push({"content" => Base64.encode(File.read(attachment[:file_path])), "type" => attachment[:mime_type].to_s, "filename" => attachment[:file_name].to_s, "disposition" => "attachment"})