bundler: Using a custom path while using system gems is unsupported - ruby-on-rails

Question

I am using GitLab-CI/CD to build my Rails application. I have noticed my builds are failing due to Using a custom path while using system gems is unsupported error, which were working perfectly fine before.
Tried to check newer update releases but didn't find any issues. Does any one have any idea on recent updates or somthing on mentioned issue?
Bellow is my gitlab-ci.yml
variables:
GIT_SUBMODULE_STRATEGY: recursive
cache:
key: ${CI_JOB_NAME}
paths:
- vendor/ruby
before_script:
- apt-get update -qq
- ruby -v
- which ruby
- gem --version
- git --version
- gem update --system 2.7.6
- gem install bundler -v 2.0.1
- bundle -v
- bundle config ${REPO_URL} ${BUNDLE_GITLAB__TOKEN}
- bundle config --global disable_shared_gems true
- bundle install --jobs $(nproc) "${FLAGS[#]}" --path vendor
rubocop:
tags:
- rubocop
script:
- bundle exec rubocop
# rspec:
# stage: test
# script:
# - bundle exec rspec
And bellow is the brief error I'm getting
$ apt-get update -qq
$ ruby -v
ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-linux]
$ which ruby
/usr/local/bin/ruby
$ gem --version
3.0.3
$ git --version
git version 2.20.1
$ gem update --system 2.7.6
Updating rubygems-update
Successfully installed rubygems-update-2.7.6
Installing RubyGems 2.7.6
Bundler 1.16.1 installed
RubyGems 2.7.6 installed
Regenerating binstubs
------------------------------------------------------------------------------
RubyGems installed the following executables:
/usr/local/bin/gem
/usr/local/bin/bundle
RubyGems system software updated
$ gem install bundler -v 2.0.1
Successfully installed bundler-2.0.1
1 gem installed
$ bundle -v
Bundler version 2.0.1
$ bundle config https://gitlab.com/dharshannn/test-star.git ${BUNDLE_GITLAB__TOKEN}
$ bundle config --global disable_shared_gems true
$ bundle install --jobs $(nproc) "${FLAGS[#]}" --path vendor
Using a custom path while using system gems is unsupported.
path:
Set for your local app (/usr/local/bundle/config): "vendor"
path.system:
Set via BUNDLE_PATH__SYSTEM: true
disable_shared_gems:
Set for the current user (/root/.bundle/config): true
ERROR: Job failed: exit code 1

Answer 1

The same happened to me today. I am pretty sure that there was no update to bundler or gem. The Docker image however has been updated (I was using ruby:2.6.3). I also added a new dependency when this started happening, so I suspect it was dependent on a gem which was already installed in the system path thus the error message.
You can get around it by specifying the following configuration variables in your .gitlab-ci.yml:
variables:
BUNDLE_DISABLE_SHARED_GEMS: "true"
BUNDLE_PATH__SYSTEM: "false"
This will configure Bundler to not use shared gems and disable system gems fully.
See https://bundler.io/v2.0/bundle_config.html
disable_shared_gems (BUNDLE_DISABLE_SHARED_GEMS): Stop Bundler from accessing gems installed to RubyGems' normal location.
and
path.system (BUNDLE_PATH__SYSTEM): Whether Bundler will install gems into the default system path (Gem.dir).