[rubygems/rubygems] Add auto_install support to require "bundler/setup"

We have some places that already use `bundle config auto_install true`,
ie:

https://github.com/technicalpickles/rubygems/blob/7a144f3374f6a400cc9832f072dc1fc0bca8c724/bundler/lib/bundler/cli.rb#L11

This applies the same logic (copy and pasted) to happen when you
`require "bundler/setup"`.

https://github.com/rubygems/rubygems/commit/bb3c922341

1 files changed, 15 insertions, 0 deletions

diff --git a/spec/bundler/runtime/setup_spec.rb b/spec/bundler/runtime/setup_spec.rb
index ccfe5d55b6..0344d24223 100644
--- a/spec/bundler/runtime/setup_spec.rb
+++ b/spec/bundler/runtime/setup_spec.rb
@@ -1599,4 +1599,19 @@ end
     sys_exec "#{Gem.ruby} #{script}", raise_on_error: false
     expect(out).to include("requiring foo used the monkeypatch")
   end
+
+  it "performs an automatic bundle install" do
+    gemfile <<-G
+      source "#{file_uri_for(gem_repo1)}"
+      gem "rack", :group => :test
+    G
+
+    bundle "config set auto_install 1"
+
+    ruby <<-RUBY
+      require 'bundler/setup'
+    RUBY
+    expect(err).to be_empty
+    expect(out).to include("Installing rack 1.0.0")
+  end
 end