Spring binstub fails when BUNDLE_APP_CONFIG is set

[mattbrictson]

Summary

The BUNDLE_APP_CONFIG environment variable, if set, tells bundler to use a different directory to store its config file (instead of the default ./.bundle). Spring does not pass this variable to its child processes. Therefore when a Spring child process requires bundler/setup, bundler does not look in the correct location for its config. This can lead to fatal errors when using spring binstubs.

Steps to reproduce

The bug can be reproduced by setting BUNDLE_APP_CONFIG and installing gems using the --path option.

We'll use Rails since it automatically sets up binstubs for us.

$ gem install rails -v 5.1.4
$ rails _5.1.4_ new binstub-error --no-rc

Setting BUNDLE_APP_CONFIG and then installing the bundle into vendor/bundle means that from hereon out bundler/setup will only work properly if BUNDLE_APP_CONFIG is honored.

$ mkdir -p /tmp/bundle-config-dir
$ export BUNDLE_APP_CONFIG=/tmp/bundle-config-dir
$ cd binstub-error
$ bundle install --path=vendor/bundle

Remove the system version of rake so that the only way to get it is via vendor/bundle:

$ gem uninstall rake --all

Notice that now the binstubs fails:

$ bin/rake --version
Could not find rake-12.2.1 in any of the sources
Run `bundle install` to install missing gems.

However bundle exec works fine:

$ bundle exec rake --version
rake, version 12.2.1

If we put the bundler config in the default location and unset BUNDLE_APP_CONFIG, the binstub now works:

$ cp -R $BUNDLE_APP_CONFIG .bundle
$ unset BUNDLE_APP_CONFIG
$ bin/rake --version
Running via Spring preloader in process 96969
rake, version 12.2.1

Workaround

Do not use BUNDLE_APP_CONFIG.

Note that Circle CI sets the BUNDLE_APP_CONFIG variable by default in its ruby:2.4.2-node-browsers docker image, so many developers could run into this bug.

[mattbrictson]

Suggested fix: #546.

[eric-hu]

I believe this bug is specific to Rubygems 2.7.1 and either Bundler 1.16.0 or 1.15.4. I've seen CI jobs that passed with 2.7.0 and 1.15.4 but fail with 2.7.1 and both 1.16.0 and 1.15.4. For Spring versions, I'm not sure of the affected range, but 2.0.2 is affected.

[AndKiel]

I've had a similar problem inside docker container.

docker-compose run web bundle exec rails c didn't want to work - bin/spring threw errors about not finding gems in any of the sources.

One solution was to run it like that docker-compose run web /bin/bash -c "unset BUNDLE_APP_CONFIG" && bundle exec rails c

Or set GEM_HOME environment variable to /bundle_cache (I had cache directory configured in docker compose file).

[temochka]

Just ran into this. Looking at the commits above, I assume that most people don’t need Spring in their Docker containers. If that is true, setting DISABLE_SPRING environment variable to 1 in Dockerfile is another possible workaround:

ENV DISABLE_SPRING 1

This way you can benefit from Spring locally but it won’t affect your containers.