已安装pry-rails仍报undefined method `pry'的Rails容器问题

问题场景 #

通过docker compose run --service-ports --detach [SERVICE_NAME]启动GitLab的Ruby on Rails Web应用容器，目标是用binding.pry断点调试源码函数。为规避初始bundle install问题，进入容器后执行gem install pry-rails安装依赖，但即便Gemfile中已引入该gem，仍触发以下错误：

==> /var/log/gitlab/gitlab-rails/production.log <==
  
ActionView::Template::Error (undefined method `pry' for #<Binding:0x00007ff556ce52b8>
Did you mean?  try):

已确认信息 #

1. pry-rails已成功安装：

root@3cbe23da9b57:/# gem list | grep pry-rails
pry-rails (0.3.9)

root@3cbe23da9b57:/# gem which pry-rails
/opt/gitlab/embedded/lib/ruby/gems/3.0.0/gems/pry-rails-0.3.9/lib/pry-rails.rb

2. Gemfile中的引入配置：

group :development, :test do
  gem 'pry-rails', '~> 0.3.9'
end

3. RubyGems环境信息：

RubyGems Environment:
  - RUBYGEMS VERSION: 3.4.14
  - RUBY VERSION: 3.0.6 (2023-03-30 patchlevel 216) [x86_64-linux]
  - INSTALLATION DIRECTORY: /opt/gitlab/embedded/lib/ruby/gems/3.0.0
  - USER INSTALLATION DIRECTORY: /root/.local/share/gem/ruby/3.0.0
  - RUBY EXECUTABLE: /opt/gitlab/embedded/bin/ruby
  - GIT EXECUTABLE: /opt/gitlab/embedded/bin/git
  - EXECUTABLE DIRECTORY: /opt/gitlab/embedded/bin
  - SPEC CACHE DIRECTORY: /root/.local/share/gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /opt/gitlab/embedded/etc
  - RUBYGEMS PLATFORMS:
     - ruby
     - x86_64-linux
  - GEM PATHS:
     - /opt/gitlab/embedded/lib/ruby/gems/3.0.0
     - /root/.local/share/gem/ruby/3.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => true
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /opt/gitlab/embedded/bin
     - /opt/gitlab/bin
     - /assets
     - /usr/local/sbin
     - /usr/local/bin
     - /usr/sbin
     - /usr/bin
     - /sbin
     - /bin

问题原因 #

1. Bundle环境未加载独立安装的gem：GitLab的Rails应用依赖bundle管理依赖，直接用gem install安装的pry-rails不在bundle的加载路径中，Rails无法识别。
2. 运行环境不匹配：日志显示应用运行在production环境，而pry-rails仅被加入development和test组，生产环境默认不会加载该组的gem。

解决方案 #

方案1：切换到开发环境并执行bundle install #

1. 重新启动容器时指定开发环境：

docker compose run --service-ports --detach -e RAILS_ENV=development [SERVICE_NAME]

2. 进入容器后执行bundle安装，让bundle识别并加载pry-rails：

docker exec [CONTAINER_ID] /bin/bash
bundle install

方案2：临时手动引入pry-rails #

在需要调试的代码前添加手动引入语句，仅作为临时调试方案：

require 'pry-rails'
binding.pry

方案3：修改Gemfile后重新构建镜像（若允许） #

如果可以重新构建镜像，调整Gemfile后执行构建，确保bundle install在镜像构建阶段完成：

1. 确保pry-rails的分组符合运行环境需求，或临时移到全局组（调试完成后改回）；
2. 重新构建Docker镜像并启动容器。

内容的提问来源于stack exchange，提问作者netcat_dd