[rubygems/rubygems] Allow enabling "Bundler 3 mode" more easily

Currently to test Bundler 3 mode we have to actually edit the version
file to simulate we're running a future version. This is inconvenient.

Instead, allow passing an environment variable, `BUNDLER_3_MODE`, to set
the "working mode" Bundler should use.

This can now be set easily by end users to enable them to try out the
changes in the future version and give us feedback.

It's unclear how version auto-switching should work when this
environment variable is set, so the auto-switching feature will be
disabled in that case.

4e92e9b209

lib/bundler/environment_preserver.rb

@@ -6,6 +6,7 @@ module Bundler
     BUNDLER_KEYS = %w[
       BUNDLE_BIN_PATH
       BUNDLE_GEMFILE
+      BUNDLER_3_MODE
       BUNDLER_VERSION
       BUNDLER_SETUP
       GEM_HOME

lib/bundler/self_manager.rb

@@ -105,6 +105,7 @@ module Bundler
 
     def autoswitching_applies?
       ENV["BUNDLER_VERSION"].nil? &&
+        ENV["BUNDLER_3_MODE"].nil? &&
         ruby_can_restart_with_same_arguments? &&
         lockfile_version
     end

lib/bundler/version.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 
 module Bundler
-  VERSION = "2.7.0.dev".freeze
+  VERSION = (ENV["BUNDLER_3_MODE"] == "true" ? "3.0.0" : "2.7.0.dev").freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= VERSION.split(".").first.to_i

spec/bundler/commands/update_spec.rb

@@ -1558,7 +1558,7 @@ RSpec.describe "bundle update --bundler" do
     G
     lockfile lockfile.sub(/(^\s*)#{Bundler::VERSION}($)/, "2.99.9")
 
-    bundle :update, bundler: true, verbose: true, preserve_ruby_flags: true
+    bundle :update, bundler: true, verbose: true, preserve_ruby_flags: true, env: { "BUNDLER_3_MODE" => nil }
 
     expect(out).to include("Updating bundler to 999.0.0")
     expect(out).to include("Running `bundle update --bundler \"> 0.a\" --verbose` with bundler 999.0.0")

spec/bundler/lock/lockfile_spec.rb

@@ -109,7 +109,7 @@ RSpec.describe "the lockfile format" do
          #{version}
     L
 
-    install_gemfile <<-G, verbose: true, preserve_ruby_flags: true
+    install_gemfile <<-G, verbose: true, preserve_ruby_flags: true, env: { "BUNDLER_3_MODE" => nil }
       source "https://gem.repo4"
 
       gem "myrack"

spec/bundler/runtime/self_management_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe "Self management" do
       "9.4.0"
     end
 
-    before do
+    around do |example|
       build_repo4 do
         build_bundler previous_minor
 
@@ -26,6 +26,8 @@ RSpec.describe "Self management" do
       G
 
       pristine_system_gems "bundler-#{current_version}"
+
+      with_env_vars("BUNDLER_3_MODE" => nil, &example)
     end
 
     it "installs locked version when using system path and uses it" do

spec/bundler/support/path.rb

@@ -265,7 +265,7 @@ module Spec
     def replace_version_file(version, dir: source_root)
       version_file = File.expand_path("lib/bundler/version.rb", dir)
       contents = File.read(version_file)
-      contents.sub!(/(^\s+VERSION\s*=\s*)"#{Gem::Version::VERSION_PATTERN}"/, %(\\1"#{version}"))
+      contents.sub!(/(^\s+VERSION\s*=\s*).*$/, %(\\1"#{version}"))
       File.open(version_file, "w") {|f| f << contents }
     end
 

test/rubygems/test_gem_commands_setup_command.rb

@@ -4,13 +4,6 @@ require_relative "helper"
 require "rubygems/commands/setup_command"
 
 class TestGemCommandsSetupCommand < Gem::TestCase
-  bundler_gemspec = File.expand_path("../../bundler/lib/bundler/version.rb", __dir__)
-  if File.exist?(bundler_gemspec)
-    BUNDLER_VERS = File.read(bundler_gemspec).match(/VERSION = "(#{Gem::Version::VERSION_PATTERN})"/)[1]
-  else
-    BUNDLER_VERS = "2.0.1"
-  end
-
   def setup
     super
 
@@ -35,7 +28,7 @@ class TestGemCommandsSetupCommand < Gem::TestCase
 
     create_dummy_files(filelist)
 
-    gemspec = util_spec "bundler", BUNDLER_VERS do |s|
+    gemspec = util_spec "bundler", "9.9.9" do |s|
       s.bindir = "exe"
       s.executables = ["bundle", "bundler"]
     end