Bundler在更新Rails时找不到当前ActiveModel

Question

正在尝试将Rails 4.2.9应用程序更新到Rails 5.2.1。已更改Gemfile：

gem 'rails', '5.2.1'

但是Bundler似乎找不到合适的ActiveModel版本(在Gemfile中的任何地方都没有专门调用)。

我已经将下面提到的gem更新到它们的最新版本(active_model_serializers、clearance、simple_form、sanitize和capybara-angular )(更新到0.2.5，因为0.2.6违反了规范)，并且测试通过了4.2.9)。

我不知道该怎么做。有什么想法？

$ bundle update rails
  ...
  Bundler could not find compatible versions for gem "activemodel":
  In Gemfile:
    active_model_serializers (= 0.10.7) was resolved to 0.10.7, which depends on
      activemodel (< 6, >= 4.1)

    clearance (= 1.16.1) was resolved to 1.16.1, which depends on
      email_validator (~> 1.4) was resolved to 1.6.0, which depends on
        activemodel

    rails (= 5.2.1) was resolved to 5.2.1, which depends on
      activemodel (= 5.2.1)

    simple_form (= 3.5.1) was resolved to 3.5.1, which depends on
      activemodel (< 5.2, > 4)

Bundler could not find compatible versions for gem "nokogiri":
  In Gemfile:
    nokogiri (= 1.7.2)

    capybara-angular (= 0.2.5) was resolved to 0.2.5, which depends on
      capybara (>= 2.5.0) was resolved to 2.18.0, which depends on
        nokogiri (>= 1.3.3)

    sanitize (= 4.6.6) was resolved to 4.6.6, which depends on
      nokogumbo (~> 1.4) was resolved to 1.5.0, which depends on
        nokogiri

    sanitize (= 4.6.6) was resolved to 4.6.6, which depends on
      nokogiri (>= 1.4.4)

    capybara-angular (= 0.2.5) was resolved to 0.2.5, which depends on
      capybara (>= 2.5.0) was resolved to 2.18.0, which depends on
        xpath (< 4.0, >= 2.0) was resolved to 2.1.0, which depends on

Answer 1

您使用的是simple_form版本3.5.1和Rails 5.2.1。version 4.0是支持Rails5.2的第一个simple_form版本。

您可以看出这就是问题所在，因为下面这行代码：

simple_form (= 3.5.1) was resolved to 3.5.1, which depends on
  activemodel (< 5.2, > 4)

将simple_form升级到4.0.0或更高版本，应可解决此问题。

大多数gem存储库都会包含一个记录此类兼容性问题的CHANGELOG，因此，第一步是访问gem的存储库，检查您是否拥有最新版本。(或者至少是一个兼容的)