Testing my understanding of how `BUNDLE_DEPLOYMENT` affects `bundle install`

README.md

I didn't expect the BUNDLE_DEPLOYMENT=true to override the BUNDLE_WITHOUT=test

It doesn't. If you call bundle list you see the correct list of gems.

docker build --build-arg BUNDLE_WITHOUT="test" --build-arg BUNDLE_DEPLOYMENT=true -t bundle-deployment-bug:env .
docker run --rm -it -e BUNDLE_DEPLOYMENT=true -e BUNDLE_WITHOUT=test bundle-deployment-bug:env

Shows that the pry gem is missing (it's in the development group) but that the minitest gem is present, even though it was set to be skipped by BUNDLE_WITHOUT=test

Dockerfile

# syntax = docker/dockerfile:1

FROM registry.docker.com/library/ruby:3.3.1-slim as base

ARG BUNDLE_DEPLOYMENT \
    BUNDLE_WITHOUT

ENV BUNDLE_DEPLOYMENT=$BUNDLE_DEPLOYMENT \
    BUNDLE_WITHOUT=$BUNDLE_WITHOUT \
    BUNDLE_PATH="/usr/local/bundle" \
    GEM_PATH="/usr/local/bundle" \
    GEM_HOME="/usr/local/bundle"

WORKDIR /rails    
FROM base as build    
COPY Gemfile Gemfile.lock ./
RUN bundle install && \
    rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git
# Copy this directory to the layer
COPY . .

FROM base    
COPY --from=build /usr/local/bundle /usr/local/bundle
COPY --from=build /rails /rails

# List the gems the Gemfile specifies
CMD ["bundle", "list"]

Gemfile

source "https://rubygems.org"

ruby "3.3.1"

group :development do
  gem "pry" 
end

group :test do
  gem "minitest"
end

gem "rake"