[rubygems/rubygems] Simulate Bundler 4 in a better way

Overriding the version constant feels too magic and creates a set of
problems. For example, Bundler will lock the simulated version, and that
can cause issues when the lockfile is used under an environment not
simulating Bundler 4 (it will try to auto-install and auto-switch to a
version that does not exist).

On top of that, it can only be configured with an ENV variable which is
not too flexible.

This commit takes a different approach of using a setting, which is
configurable through ENV or `bundle config`, and pass the simulated
version to `Bundler::FeatureFlag`. The real version is still the one set
by `VERSION`, but anything that `Bundler::FeatureFlag` controls will use
the logic of the "simulated version".

In particular, all feature flags and deprecation messages will respect
the simulated version, and this is exactly the set of functionality that
we want users to be able to easily try before releasing it.

8129402193

lib/bundler.rb

@@ -567,7 +567,7 @@ module Bundler
     end
 
     def feature_flag
-      @feature_flag ||= FeatureFlag.new(VERSION)
+      @feature_flag ||= FeatureFlag.new(settings[:simulate_version] || VERSION)
     end
 
     def reset!

lib/bundler/environment_preserver.rb

@@ -6,7 +6,6 @@ module Bundler
     BUNDLER_KEYS = %w[
       BUNDLE_BIN_PATH
       BUNDLE_GEMFILE
-      BUNDLER_4_MODE
       BUNDLER_VERSION
       BUNDLER_SETUP
       GEM_HOME

lib/bundler/feature_flag.rb

@@ -50,6 +50,8 @@ module Bundler
       @major_version >= target_major_version
     end
 
+    attr_reader :bundler_version
+
     def initialize(bundler_version)
       @bundler_version = Gem::Version.create(bundler_version)
       @major_version = @bundler_version.segments.first

lib/bundler/self_manager.rb

@@ -98,7 +98,6 @@ module Bundler
 
     def autoswitching_applies?
       ENV["BUNDLER_VERSION"].nil? &&
-        ENV["BUNDLER_4_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 = (ENV["BUNDLER_4_MODE"] == "true" ? "4.0.0" : "2.7.0.dev").freeze
+  VERSION = "2.7.0.dev".freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= gem_version.segments.first

spec/bundler/bundler/settings_spec.rb

@@ -333,7 +333,7 @@ that would suck --ehhh=oh geez it looks like i might have broken bundler somehow
       C
 
       expect(Bundler.ui).not_to receive(:warn)
-      expect(settings.all).to be_empty
+      expect(settings.all).to eq(simulated_version ? ["simulate_version"] : [])
     end
 
     it "converts older keys with dashes" do

spec/bundler/commands/config_spec.rb

@@ -453,7 +453,7 @@ E
     it "does not make bundler crash and ignores the configuration" do
       bundle "config list --parseable"
 
-      expect(out).to be_empty
+      expect(out).to eq(simulated_version ? "simulate_version=#{simulated_version}" : "")
       expect(err).to be_empty
 
       ruby(<<~RUBY)
@@ -476,26 +476,38 @@ E
   describe "subcommands" do
     it "list" do
       bundle "config list", env: { "BUNDLE_FOO" => "bar" }
-      expect(out).to eq "Settings are listed in order of priority. The top value will be used.\nfoo\nSet via BUNDLE_FOO: \"bar\""
+      expected = "Settings are listed in order of priority. The top value will be used.\nfoo\nSet via BUNDLE_FOO: \"bar\""
+      expected += "\n\nsimulate_version\nSet via BUNDLE_SIMULATE_VERSION: \"#{simulated_version}\"" if simulated_version
+      expect(out).to eq(expected)
 
       bundle "config list", env: { "BUNDLE_FOO" => "bar" }, parseable: true
-      expect(out).to eq "foo=bar"
+      expected = "foo=bar"
+      expected += "\nsimulate_version=#{simulated_version}" if simulated_version
+      expect(out).to eq(expected)
     end
 
     it "list with credentials" do
       bundle "config list", env: { "BUNDLE_GEMS__MYSERVER__COM" => "user:password" }
-      expect(out).to eq "Settings are listed in order of priority. The top value will be used.\ngems.myserver.com\nSet via BUNDLE_GEMS__MYSERVER__COM: \"user:[REDACTED]\""
+      expected = "Settings are listed in order of priority. The top value will be used.\ngems.myserver.com\nSet via BUNDLE_GEMS__MYSERVER__COM: \"user:[REDACTED]\""
+      expected += "\n\nsimulate_version\nSet via BUNDLE_SIMULATE_VERSION: \"#{simulated_version}\"" if simulated_version
+      expect(out).to eq(expected)
 
       bundle "config list", parseable: true, env: { "BUNDLE_GEMS__MYSERVER__COM" => "user:password" }
-      expect(out).to eq "gems.myserver.com=user:password"
+      expected = "gems.myserver.com=user:password"
+      expected += "\nsimulate_version=#{simulated_version}" if simulated_version
+      expect(out).to eq(expected)
     end
 
     it "list with API token credentials" do
       bundle "config list", env: { "BUNDLE_GEMS__MYSERVER__COM" => "api_token:x-oauth-basic" }
-      expect(out).to eq "Settings are listed in order of priority. The top value will be used.\ngems.myserver.com\nSet via BUNDLE_GEMS__MYSERVER__COM: \"[REDACTED]:x-oauth-basic\""
+      expected = "Settings are listed in order of priority. The top value will be used.\ngems.myserver.com\nSet via BUNDLE_GEMS__MYSERVER__COM: \"[REDACTED]:x-oauth-basic\""
+      expected += "\n\nsimulate_version\nSet via BUNDLE_SIMULATE_VERSION: \"#{simulated_version}\"" if simulated_version
+      expect(out).to eq(expected)
 
       bundle "config list", parseable: true, env: { "BUNDLE_GEMS__MYSERVER__COM" => "api_token:x-oauth-basic" }
-      expect(out).to eq "gems.myserver.com=api_token:x-oauth-basic"
+      expected = "gems.myserver.com=api_token:x-oauth-basic"
+      expected += "\nsimulate_version=#{simulated_version}" if simulated_version
+      expect(out).to eq(expected)
     end
 
     it "get" do

spec/bundler/lock/lockfile_spec.rb

@@ -109,7 +109,7 @@ RSpec.describe "the lockfile format" do
          #{version}
     L
 
-    install_gemfile <<-G, verbose: true, env: { "BUNDLER_4_MODE" => nil }
+    install_gemfile <<-G, verbose: true
       source "https://gem.repo4"
 
       gem "myrack"

spec/bundler/realworld/slow_perf_spec.rb

@@ -131,14 +131,8 @@ RSpec.describe "bundle install with complex dependencies", realworld: true do
       end
     G
 
-    if Bundler.feature_flag.bundler_4_mode?
-      bundle "lock", env: { "DEBUG_RESOLVER" => "1" }, raise_on_error: false
+    bundle "lock", env: { "DEBUG_RESOLVER" => "1" }
 
-      expect(out).to include("backtracking").exactly(26).times
-    else
-      bundle "lock", env: { "DEBUG_RESOLVER" => "1" }
-
-      expect(out).to include("Solution found after 10 attempts")
-    end
+    expect(out).to include("Solution found after 10 attempts")
   end
 end

spec/bundler/runtime/self_management_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe "Self management" do
       "9.4.0"
     end
 
-    around do |example|
+    before do
       build_repo4 do
         build_bundler previous_minor
 
@@ -26,8 +26,6 @@ RSpec.describe "Self management" do
       G
 
       pristine_system_gems "bundler-#{current_version}"
-
-      with_env_vars("BUNDLER_4_MODE" => nil, &example)
     end
 
     it "installs locked version when using system path and uses it" do

spec/bundler/support/env.rb

@@ -9,5 +9,9 @@ module Spec
     def rubylib
       ENV["RUBYLIB"].to_s.split(File::PATH_SEPARATOR)
     end
+
+    def simulated_version
+      ENV["BUNDLE_SIMULATE_VERSION"]
+    end
   end
 end

spec/bundler/support/filters.rb

@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 class RequirementChecker < Proc
-  def self.against(present, major_only: false)
-    present = present.split(".")[0] if major_only
-    provided = Gem::Version.new(present)
+  def self.against(provided, major_only: false)
+    provided = Gem::Version.new(provided.segments.first) if major_only
 
     new do |required|
       requirement = Gem::Requirement.new(required)
@@ -28,8 +27,8 @@ end
 RSpec.configure do |config|
   config.filter_run_excluding realworld: true
 
-  config.filter_run_excluding bundler: RequirementChecker.against(Bundler::VERSION, major_only: true)
-  config.filter_run_excluding rubygems: RequirementChecker.against(Gem::VERSION)
+  config.filter_run_excluding bundler: RequirementChecker.against(Bundler.feature_flag.bundler_version, major_only: true)
+  config.filter_run_excluding rubygems: RequirementChecker.against(Gem.rubygems_version)
   config.filter_run_excluding ruby_repo: !ENV["GEM_COMMAND"].nil?
   config.filter_run_excluding no_color_tty: Gem.win_platform? || !ENV["GITHUB_ACTION"].nil?
   config.filter_run_excluding permissions: Gem.win_platform?