empty charset fix

lib/mail/header.rb

@@ -169,7 +169,11 @@ def []=(name, value)
  def charset=(val)
  params = self[:content_type].parameters rescue nil
  if params
- params[:charset] = val
+ if val
+ params[:charset] = val
+ else
+ params.delete(:charset)
+ end
  end
  @charset = val
  end

lib/mail/message.rb

@@ -1477,7 +1477,9 @@ def add_charset
  warning = "Non US-ASCII detected and no charset defined.\nDefaulting to UTF-8, set your own if this is incorrect.\n"
  warn(warning)
  end
- header[:content_type].parameters['charset'] = @charset
+ if @charset
+ header[:content_type].parameters['charset'] = @charset
+ end
  end
  end
 

spec/mail/message_spec.rb

@@ -1437,6 +1437,39 @@ def message_headers_should_match(message, other)
  expect(mail.parts.last.content_transfer_encoding).to match(/7bit|8bit|binary/)
  end
 
+ describe 'charset=' do
+ before do
+ @mail = Mail.new do
+ to 'mikel@test.lindsaar.net'
+ from 'bob@test.lindsaar.net'
+ subject 'Multipart email'
+ text_part do
+ body 'This is plain text'
+ end
+ html_part do
+ content_type 'text/html; charset=UTF-8'
+ body '<h1>This is HTML</h1>'
+ end
+ end
+ end
+
+ it "should not add an empty charset header" do
+ @mail.charset = nil
+
+ expect(@mail.multipart?).to eq true
+ expect(@mail.parts.count).to eq 2
+ expect(@mail.encoded.scan(/charset=UTF-8/).count).to eq 2
+ end
+
+ it "should remove the charset header" do
+ @mail.charset = 'iso-8859-1'
+ @mail.charset = nil
+
+ expect(@mail.encoded.scan(/charset=UTF-8/).count).to eq 2
+ expect(@mail.encoded.scan(/charset=iso-8859-1/).count).to eq 0
+ end
+ end
+
  describe "convert_to_multipart" do
  subject do
  read_fixture('emails', 'attachment_emails', 'attachment_only_email.eml').tap(&:convert_to_multipart)