Bundler original_env.GEM_HOME is incorrect if bundler version is trampolined

[shanesmith]

Describe the problem as clearly as you can

The value for Bundler.original_env['GEM_HOME'] is incorrect in the following scenario:

• The BUNDLED WITH version found in Gemfile.lock is not installed in the Gem Path
• The BUNDLE_PATH (or BUNDLE_DEPLOYMENT) is set
• The script is executed with bundle exec

The impact is that system gems can't be run with Bundle.unbundled_X, which is how the issue was first encountered.

gem install ejson2env
bundle exec ruby -e 'Bundler.unbundled_system("ejson2env")
# [...] can't find gem ejson2env (>= 0.a) with executable ejson2env (Gem::GemNotFoundException)

Did you try upgrading rubygems & bundler?

Yes

Post steps to reproduce the problem

FROM ruby:3.2.2-bullseye

RUN mkdir /app

COPY <<EOF /app/Gemfile
source "https://rubygems.org"
gem "a", "~> 0.2.8"
EOF

COPY <<EOF /app/Gemfile.lock
GEM
  remote: https://rubygems.org/
  specs:
    a (0.2.8)

PLATFORMS
  ruby

DEPENDENCIES
  a (~> 0.2.8)

BUNDLED WITH
   2.4.0
EOF

RUN gem update --system

ENV BUNDLE_PATH '/vendor/bundle'

RUN cd app && bundle install

Which command did you run?

docker build -t foo . && docker run -i foo bash - <<'EOF'
echo -n "system: "
bundle version

cd app

echo -n "app: "
bundle version

echo -n "GEM_HOME: "
echo $GEM_HOME

echo -n "original_env.GEM_HOME: "
bundle exec ruby -e 'puts Bundler.original_env["GEM_HOME"]'
EOF

What were you expecting to happen?

Expected output to be:

system: Bundler version 2.5.7 (2024-03-22 commit 199531f621)
app: Bundler version 2.4.0 (2022-12-24 commit e67004d0fe)
GEM_HOME: /usr/local/bundle
original_env.GEM_HOME: /usr/local/bundle

What actually happened?

Actual output is:

system: Bundler version 2.5.7 (2024-03-22 commit 199531f621)
app: Bundler version 2.4.0 (2022-12-24 commit e67004d0fe)
GEM_HOME: /usr/local/bundle
original_env.GEM_HOME: /vendor/bundle/ruby/3.2.0

Other notes

I know of a couple workarounds, any of these fixes the issue:

1. Set BUNDLE_VERSION=system
2. Pre-install the BUNDLED WITH version (ex: gem install bundler:2.4.0)
3. Use -rbundler/setup instead of bundle exec (ex: ruby -rbundler/setup -e 'puts Bundler.original_env["GEM_HOME"]')

If not included with the output of your command, run bundle env and paste the output below

Environment

Bundler       2.4.0
  Platforms   ruby, aarch64-linux
Ruby          3.2.2p53 (2023-03-30 revision e51014f9c05aa65cbf203442d37fef7c12390015) [aarch64-linux]
  Full Path   /usr/local/bin/ruby
  Config Dir  /usr/local/etc
RubyGems      3.5.7
  Gem Home    /vendor/bundle/ruby/3.2.0
  Gem Path    /vendor/bundle/ruby/3.2.0
  User Home   /root
  User Path   /root/.local/share/gem/ruby/3.2.0
  Bin Dir     /vendor/bundle/ruby/3.2.0/bin
Tools
  Git         2.30.2
  RVM         not installed
  rbenv       not installed
  chruby      not installed

Bundler Build Metadata

Built At          2022-12-24
Git SHA           e67004d0fe
Released Version  true

Bundler settings

app_config
  Set via BUNDLE_APP_CONFIG: "/usr/local/bundle"
path
  Set via BUNDLE_PATH: "/vendor/bundle"
silence_root_warning
  Set via BUNDLE_SILENCE_ROOT_WARNING: true