`ActionMailer.deliver_all_later` inline processes mailers before enqueuing

[chaadow]

related to #55448

Steps to reproduce

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  # gem "rails", github: 'rails/rails'
  # If you want to test against edge Rails replace the previous line with this:
  gem "rails", github: "rails/rails", branch: "main"
  gem "net-smtp", github: "ruby/net-smtp", ref: "d496a829f9b99adb44ecc1768c4d005e5f7b779e", require: false
end

require "action_mailer/railtie"
require "minitest/autorun"

class TestApp < Rails::Application
  config.load_defaults Rails::VERSION::STRING.to_f
  config.root = __dir__
  config.eager_load = false
  config.hosts << "example.org"
  config.secret_key_base = "secret_key_base"

  config.logger = Logger.new($stdout)
end
Rails.application.initialize!

$should_not_be_run = false

class TestMailer < ActionMailer::Base
  attr_accessor :should_not_be_run
  def hello_world
    @message = "Hello, world"

    $should_not_be_run = true

    mail from: "test@example.com", to: "user@example.com" do |format|
      format.html { render inline: "<h1><%= @message %></h1>" }
      format.text { render inline: "<%= @message %>" }
    end
  end
end

class BugTest < ActionMailer::TestCase
  test "Does not run hello_world when calling deliver_all_later" do
    email = TestMailer.hello_world

    ActionMailer.deliver_all_later([email])

    assert_not $should_not_be_run
  end
end

Expected behavior

When I can ActionMailer.deliver_all_later([mailer1, mailer2]) it should not process and execute the mailer

Actual behavior

• mailers are called
• mailers are enqueued through the job adapter

So double processing : Inline ( similar to deliver_now ) and "later" by enqueuing in the job adapter

System configuration

Rails version: main aedfc4af7625312bfdec087a0d03e5ad5da80027

Ruby version: 3.4.5