由于缺少 Mime JSON，rake 任务无法启动答案

【问题标题】：rake task does not launch for lack of Mime JSON由于缺少 Mime JSON，rake 任务无法启动
【发布时间】：2020-12-11 12:06:34
【问题描述】：

在本地安装存储库并为 rails 4.0 应用程序捆绑后，数据库创建

rake db:create

命令失败，返回以下错误：

uninitialized constant Mime::JSON

从 application.rb 这个特定的行调用

Bundler.require(:default, Rails.env)

这一行的前面是：

require File.expand_path('../boot', __FILE__)

require 'rails/all'

如何让 rake 正确处理？

** 更新 ** 根据请求完整的堆栈跟踪如下。我确实通过删除 jbuilder gem 来避免错误。

NameError: uninitialized constant Mime::JSON
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/jbuilder-1.5.3/lib/jbuilder/jbuilder_template.rb:110:in `<class:JbuilderHandler>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/jbuilder-1.5.3/lib/jbuilder/jbuilder_template.rb:108:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/jbuilder-1.5.3/lib/jbuilder.rb:358:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `require'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `block (2 levels) in require'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `each'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `block in require'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `each'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `require'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler.rb:174:in `require'
/Volumes/Mo/r/uelcom/config/application.rb:7:in `<top (required)>'
/Volumes/Mo/r/uelcom/Rakefile:8:in `require'
/Volumes/Mo/r/uelcom/Rakefile:8:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/rake_module.rb:29:in `load'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/rake_module.rb:29:in `load_rakefile'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:703:in `raw_load_rakefile'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:104:in `block in load_rakefile'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:186:in `standard_exception_handling'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:103:in `load_rakefile'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:82:in `block in run'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:186:in `standard_exception_handling'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:80:in `run'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/bin/rake:23:in `load'
/Users/deploy/.rbenv/versions/2.6.1/bin/rake:23:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:63:in `load'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:63:in `kernel_load'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:28:in `run'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli.rb:476:in `exec'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor.rb:399:in `dispatch'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli.rb:30:in `dispatch'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/base.rb:476:in `start'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/cli.rb:24:in `start'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/exe/bundle:46:in `block in <top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/friendly_errors.rb:123:in `with_friendly_errors'
/Users/deploy/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/exe/bundle:34:in `<top (required)>'
/Users/deploy/.rbenv/versions/2.6.1/bin/bundle:23:in `load'
/Users/deploy/.rbenv/versions/2.6.1/bin/bundle:23:in `<main>'

【问题讨论】：

能否请您添加异常的完整回溯？
问题已更新。
你能分享你的Gemfile吗
您使用的是 Rails 5 及以上版本吗？
no 4.0...有点乱，因为弹出了许多宝石和问题。

标签： ruby-on-rails ruby-on-rails-4 rake

【解决方案1】：

看来您使用的是 rails 5 或更高版本。

从 Rails 版本 5 或更高版本开始，不推荐通过 Mime::JSON 访问 Mime 类型，我们需要以 Mime[:json] 访问它

请找到以下相同的参考资料 - Release Note 和 Pull request

不推荐通过常量访问 mime 类型（例如 Mime::HTML）。使用带符号的下标运算符（例如 Mime[:html]）

根据您给出的异常的回溯，gem jbuilder 导致了问题，它以 Mime::JSON 访问 Mime 类型，已弃用。

请在 gem jbuilder 上找到导致错误的行的引用 - Jubilder - Github。

您使用的是旧版本的jbuilder(1.5.3)，请将此 gem 升级到最新版本并尝试

试试下面的版本：

宝石文件

gem 'jbuilder', '~> 2.10'

【讨论】：