[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"`.

rubygems/rubygems@bb3c922341

lib/bundler.rb

@@ -40,6 +40,7 @@ module Bundler
   SUDO_MUTEX = Thread::Mutex.new
 
   autoload :Checksum,               File.expand_path("bundler/checksum", __dir__)
+  autoload :CLI,                    File.expand_path("bundler/cli", __dir__)
   autoload :CIDetector,             File.expand_path("bundler/ci_detector", __dir__)
   autoload :Definition,             File.expand_path("bundler/definition", __dir__)
   autoload :Dependency,             File.expand_path("bundler/dependency", __dir__)
@@ -165,6 +166,25 @@ def setup(*groups)
       end
     end
 
+    # Automatically install dependencies if Bundler.settings[:auto_install] exists.
+    # This is set through config cmd `bundle config set --global auto_install 1`.
+    #
+    # Note that this method `nil`s out the global Definition object, so it
+    # should be called first, before you instantiate anything like an
+    # `Installer` that'll keep a reference to the old one instead.
+    def auto_install
+      return unless settings[:auto_install]
+
+      begin
+        definition.specs
+      rescue GemNotFound, GitError
+        ui.info "Automatically installing missing gems."
+        reset!
+        CLI::Install.new({}).run
+        reset!
+      end
+    end
+
     # Setups Bundler environment (see Bundler.setup) if it is not already set,
     # and loads all gems from groups specified. Unlike ::setup, can be called
     # multiple times with different groups (if they were allowed by setup).

lib/bundler/cli.rb

@@ -5,6 +5,7 @@
 module Bundler
   class CLI < Thor
     require_relative "cli/common"
+    require_relative "cli/install"
 
     package_name "Bundler"
 
@@ -69,7 +70,7 @@ def initialize(*args)
       Bundler.settings.set_command_option_if_given :retry, options[:retry]
 
       current_cmd = args.last[:current_command].name
-      auto_install if AUTO_INSTALL_CMDS.include?(current_cmd)
+      Bundler.auto_install if AUTO_INSTALL_CMDS.include?(current_cmd)
     rescue UnknownArgumentError => e
       raise InvalidOption, e.message
     ensure
@@ -737,26 +738,6 @@ def self.deprecated_ext_value?(arguments)
 
     private
 
-    # Automatically invoke `bundle install` and resume if
-    # Bundler.settings[:auto_install] exists. This is set through config cmd
-    # `bundle config set --global auto_install 1`.
-    #
-    # Note that this method `nil`s out the global Definition object, so it
-    # should be called first, before you instantiate anything like an
-    # `Installer` that'll keep a reference to the old one instead.
-    def auto_install
-      return unless Bundler.settings[:auto_install]
-
-      begin
-        Bundler.definition.specs
-      rescue GemNotFound, GitError
-        Bundler.ui.info "Automatically installing missing gems."
-        Bundler.reset!
-        invoke :install, []
-        Bundler.reset!
-      end
-    end
-
     def current_command
       _, _, config = @_initializer
       config[:current_command]

lib/bundler/setup.rb

@@ -5,6 +5,9 @@
 if Bundler::SharedHelpers.in_bundle?
   require_relative "../bundler"
 
+  # try to auto_install first before we get to the `Bundler.ui.silence`, so user knows what is happening
+  Bundler.auto_install
+
   if STDOUT.tty? || ENV["BUNDLER_FORCE_TTY"]
     begin
       Bundler.ui.silence { Bundler.setup }

spec/bundler/runtime/setup_spec.rb

@@ -1599,4 +1599,19 @@ def require(path)
     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