Elixir mailgun 错误：IO.chardata_to_string/1 中没有匹配的函数子句答案

【问题标题】：Elixir mailgun error: no function clause matching in IO.chardata_to_string/1Elixir mailgun 错误：IO.chardata_to_string/1 中没有匹配的函数子句
【发布时间】：2015-12-02 15:53:22
【问题描述】：

当我尝试通过 mailgun 库发送电子邮件时，我收到错误：** (FunctionClauseError) no function clause matching in IO.chardata_to_string/1

我在测试中发现了这个问题：

test/mailers/mailer_test.ex

defmodule Myapp.MailerTest do
  use Myapp.ModelCase

  test "mailer test" do
    Myapp.Mailer.invitation_email("abc.com", "foo@bar.com")
  end
end

lib/mailer.ex

defmodule Myapp.Mailer do
  use Mailgun.Client, domain: "abc.mailgun.org",
                      key: "key-abc",
                      mode: :test,
                      mailgun_test_file_path: "mail.json"

  def invitation_email(host, to_email) do
    send_email to: to_email,
               from: "hi@#{host}",
               subject: "Invitation!",
               html: "<strong>Welcome</strong>"
  end
end

测试运行：

$ mix test test/mailers/mailer_test.ex                                                                                                     
Compiled lib/mailer.ex
Generated myapp app

  1) test mailer test (Myapp.MailerTest)
     test/mailers/mailer_test.ex:4
     ** (FunctionClauseError) no function clause matching in IO.chardata_to_string/1
     stacktrace:
       (elixir) lib/io.ex:333: IO.chardata_to_string(nil)
       (elixir) lib/file.ex:701: File.write/3
       lib/client.ex:22: Mailgun.Client.do_send_email/3
       test/mailers/mailer_test.ex:5

Finished in 0.2 seconds (0.1s on load, 0.01s on tests)
1 test, 1 failure

Randomized with seed 182269

另外，顺便说一句，如果我删除 mode 参数，错误就会消失。但它也不发送电子邮件。

【问题讨论】：

标签： phoenix-framework elixir

【解决方案1】：

mailgun_test_file_path: "mail.json"

应该是：

test_file_path: "mail.json"

https://github.com/chrismccord/mailgun#test-mode

【讨论】：