bundler error when spring: true is combined with bundler v1.12 in Rails 4.2 environment

[rmm5t]

Steps to reproduce:

1. gem update --system
2. gem install bundler --version "~> 1.12.5"
3. Configure a Guardfile with guard :minitest, spring: true on a Rails 4.2 environment

Expected Behavior:

• Test suite should run as expected, and use spring to run tests faster on each invocation

Actual Behavior:

require: cannot load such file -- bundler/setup

09:42:26 - INFO - Guard::Minitest 2.4.4 is running, with Minitest::Unit 5.9.0!
09:42:26 - INFO - Running: all tests
/Users/{user}/.rbenv/versions/2.2.5/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- bundler/setup (LoadError)
    from /Users/{user}/.rbenv/versions/2.2.5/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /Users/{user}/work/{myapp}/config/boot.rb:3:in `<top (required)>'
    from bin/rake:6:in `require_relative'
    from bin/rake:6:in `<main>'

Known Workaround Option 1: (downgrade bundler)

1. gem uninstall -Ix bundler
2. gem install bundler --version "~> 1.11.2"

Known Workaround Option 2: (turn off spring, resulting in slower tests)

• Remove spring: true from Guardfile

[rmm5t]

Update: I suspect this might be related to rubygems/bundler#4602

[e2]

I'm guessing it's because of this line:

https://github.com/guard/guard-minitest/blob/2db91fb/lib/guard/minitest/runner.rb#L135

Here's a fix: guard/guard-rspec#378

See this issue: guard/guard-rspec#369

[e2]

If you can prepare a PR based on the fix above, I can make a quick bugfix release.

I believe with_clean_env has been replaceable since forever, so I believe the config option can be skipped. (I haven't researched the differences much).

[rmm5t]

Thanks @e2. Good pointer. I'll prepare a PR as soon as I can get to it.

[rmm5t]

@e2 PR submitted at #140. Skipped the extra config option. Thanks!

[e2]

FYI, I think bugs like this can now be reproduced with gem_isolator, like I used for guard_rspec:

guard/guard-rspec@f565af6

I'll merge the PR without it, but from experience I know it's helpful to reproduce LOAD_PATH and bundler issues which Guard::Minitest is especially prone to.

Thanks again!

[e2]

Released (v2.4.5). Let me know if there's anything else ;)

[rmm5t]

@e2 Thanks for super-fast turnaround.

[e2]

My pleasure :)