帶有ical附件的多部分電子郵件顯示不正確

我不確定這是否是我的代碼ActionMailer、Mail甚至icalendar gem 的問題？

用戶注冊一個活動，他們會收到一封帶有 ical 附件的電子郵件：

# app/mailers/registration_mailer.rb

class RegistrationMailer < ApplicationMailer
  helper MailerHelper

  def created(registration)
    ...

    cal = Icalendar::Calendar.new
    cal.event do |e|
      e.dtstart = @event.start_time
      e.dtend = @event.end_time
      e.organizer = 'mailto:[email protected]'
      e.attendee = @recipient
      e.location = @location.addr_one_liner
      e.summary = @summary
      e.description = @description
    end
    cal.append_custom_property('METHOD', 'REQUEST')
    mail.attachments[@attachment_title] = { mime_type: 'text/calendar', content: cal.to_ical }

    mail(to: @recipient.email, subject: "[20 Liters] You registered for a filter build on #{@event.mailer_time}")
  end

  ...
end

我有文本和 HTML 視圖：

• app/views/registration_mailer/created.text.erb
• app/views/registration_mailer/created.html.erb

當我省略附件時，電子郵件的結構如下：

Header stuff...
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_63358693571_1146901122e"; charset=UTF-8
Content-Transfer-Encoding: 7bit

----==_mimepart_63358693571_1146901122e
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the text version of the email here]

----==_mimepart_63358693571_1146901122e
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the HTML version of the email here]
----==_mimepart_63358693571_1146901122e--

當附件存在時，電子郵件的結構如下：

Header stuff...
Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="--==_mimepart_6335c3388b140_114924286ed"; charset=UTF-8
Content-Transfer-Encoding: 7bit

----==_mimepart_6335c3388b140_114924286ed
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the text version of the email here]

----==_mimepart_6335c3388b140_114924286ed
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the HTML version of the email here]

----==_mimepart_6335c3388b140_114924286ed
Content-Type: multipart/alternative; boundary="--==_mimepart_6335c3389bc30_114924287a3"; charset=UTF-8
Content-Transfer-Encoding: 7bit

----==_mimepart_6335c3389bc30_114924287a3
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the text version of the email AGAIN]

----==_mimepart_6335c3389bc30_114924287a3
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit

[the HTML version of the email AGAIN]

----==_mimepart_6335c3389bc30_114924287a3--
----==_mimepart_6335c3388b140_114924286ed
Content-Type: text/calendar; charset=UTF-8
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=20Liters_filterbuild_20221011T0900.ical
Content-ID: <6335[email protected]>

[numbers and letters]
----==_mimepart_6335c3388b140_114924286ed--

突然是一棵奇怪的樹：

1. Content-Type: multipart/mixed
    A. Content-Type: text/plain
    B. Content-Type: text/html
    C. Content-Type: multipart/alternative
        i. Content-Type: text/plain
        ii. Content-Type: text/html
    D. Content-Type: text/calendar

Rails 的郵件預覽不會重現此問題，使用 Litmus 的電子郵件客戶端預覽也不會（因為它似乎洗掉了文本部分和附件），但我假設內容型別的變形結構不僅僅是特定于客戶端的渲染問題。

我認為這是來自 ActionMailer 下面的 Mail gem 奇怪地構造了內容型別，但我在這里有點超出我的深度。可能是ActionMailer，我真的不知道該怎么說。

我不是很精通這個，但我想我想要這個結構：

1. Content-Type: multipart/mixed
    A. Content-Type: multipart/alternative
        i. Content-Type: text/plain
        ii. Content-Type: text/html
    B. Content-Type: text/calendar

所以，兩個問題：

1.如果是我的代碼，我做錯了什么？

2.如果不是我的代碼，我可以強制我想要的結構嗎？

我一直在梳理 ActionMailer 和 Mail 代碼庫，但還沒有找到一種方法將我的電子郵件手動形成到這個級別。

uj5u.com熱心網友回復：

經過更多的挖掘，我責怪ActionMailer，盡管我仍然不確定為什么 text 和 html 部分被添加了兩次。

我特定用途的猴子補丁是讓 ActionMailer 和 Mail 構建mail物件，然后手動洗掉不需要的部分：

# app/mailers/registration_mailer.rb

...

mail.attachments[@attachment_title] = { mime_type: 'text/calendar', content: cal.to_ical }

mail(to: @recipient.email, subject: "[20 Liters] You registered for a filter build on #{@event.mailer_time}")

# PATCH: text and html parts are getting inserted in multipart/mixed (top level) as well as multipart/alternative (2nd level)
mail.parts.reject! { |part| !part.attachment? && !part.multipart? }

這僅適用于我的具體情況。如果mail為您創建的嵌套不同，則您的reject!陳述句將需要不同。

在我的例子中，mail構建這個結構：

1. Content-Type: multipart/mixed
    A. Content-Type: text/plain
    B. Content-Type: text/html
    C. Content-Type: multipart/alternative
        i. Content-Type: text/plain
        ii. Content-Type: text/html
    D. Content-Type: text/calendar

所以我進入第一級（A. - D.）并拒絕任何不是多部分且不是附件的部分：

1. Content-Type: multipart/mixed
    A. Content-Type: text/plain <-- not multipart, not attachment = rejected
    B. Content-Type: text/html <-- not multipart, not attachment = rejected
    C. Content-Type: multipart/alternative  <-- is multipart, not attachment = kept
        i. Content-Type: text/plain
        ii. Content-Type: text/html
    D. Content-Type: text/calendar  <-- not multipart, is attachment = kept

如果您遇到此問題，我建議您使用除錯器來檢查您的mail物件，特別關注parts. 請記住，它parts可以是深度嵌套的。

Mail::Part繼承Mail::Message其中有一些有用的方法可以用來確定訊息的“形狀”：

• multipart?
• attachment?
• attachments
• has_attachments?
• boundary
• parts
• all_parts

還有祝你好運。

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