Add FeatureFlag classseg-feature-flag

Main use will be code showing what is true setting vs what is flagged

Also can be used to develop for future major versions without needing a separate dev branch

9 files changed, 40 insertions, 8 deletions

diff --git a/lib/bundler.rb b/lib/bundler.rb
index 8b3f60d36a..18b9e75253 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -27,6 +27,7 @@ module Bundler
   autoload :EndpointSpecification,  "bundler/endpoint_specification"
   autoload :Env,                    "bundler/env"
   autoload :Fetcher,                "bundler/fetcher"
+  autoload :FeatureFlag,            "bundler/feature_flag"
   autoload :GemHelper,              "bundler/gem_helper"
   autoload :GemHelpers,             "bundler/gem_helpers"
   autoload :GemVersionPromoter,     "bundler/gem_version_promoter"
@@ -389,6 +390,10 @@ EOF
       @git_present = Bundler.which("git") || Bundler.which("git.exe")
     end
 
+    def feature_flag
+      @feature_flag ||= FeatureFlag.new(VERSION)
+    end
+
     def reset!
       @root = nil
       @settings = nil
diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index 75cceee80d..11edbeb13f 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -92,7 +92,7 @@ module Bundler
     end
 
     def self.handle_no_command_error(command, has_namespace = $thor_runner)
-      if Bundler.settings[:plugins] && Bundler::Plugin.command?(command)
+      if Bundler.feature_flag.plugins? && Bundler::Plugin.command?(command)
         return Bundler::Plugin.exec_command(command, ARGV[1..-1])
       end
 
@@ -491,7 +491,7 @@ module Bundler
       Doctor.new(options).run
     end
 
-    if Bundler.settings[:plugins]
+    if Bundler.feature_flag.plugins?
       require "bundler/cli/plugin"
       desc "plugin SUBCOMMAND ...ARGS", "manage the bundler plugins"
       subcommand "plugin", Plugin
diff --git a/lib/bundler/cli/install.rb b/lib/bundler/cli/install.rb
index 5c7b8c5b0b..9802ea8036 100644
--- a/lib/bundler/cli/install.rb
+++ b/lib/bundler/cli/install.rb
@@ -63,7 +63,7 @@ module Bundler
       # rubygems plugins sometimes hook into the gem install process
       Gem.load_env_plugins if Gem.respond_to?(:load_env_plugins)
 
-      Plugin.gemfile_install(Bundler.default_gemfile) if Bundler.settings[:plugins]
+      Plugin.gemfile_install(Bundler.default_gemfile) if Bundler.feature_flag.plugins?
 
       definition = Bundler.definition
       definition.validate_ruby!
diff --git a/lib/bundler/cli/update.rb b/lib/bundler/cli/update.rb
index 1c35659e0b..c2bf88ff18 100644
--- a/lib/bundler/cli/update.rb
+++ b/lib/bundler/cli/update.rb
@@ -10,7 +10,7 @@ module Bundler
     def run
       Bundler.ui.level = "error" if options[:quiet]
 
-      Plugin.gemfile_install(Bundler.default_gemfile) if Bundler.settings[:plugins]
+      Plugin.gemfile_install(Bundler.default_gemfile) if Bundler.feature_flag.plugins?
 
       sources = Array(options[:source])
       groups  = Array(options[:group]).map(&:to_sym)
diff --git a/lib/bundler/feature_flag.rb b/lib/bundler/feature_flag.rb
new file mode 100644
index 0000000000..80bf2a5150
--- /dev/null
+++ b/lib/bundler/feature_flag.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+module Bundler
+  class FeatureFlag
+    def self.settings_flag(flag)
+      unless Bundler::Settings::BOOL_KEYS.include?(flag.to_s)
+        raise "Cannot use `#{flag}` as a settings feature flag since it isn't a bool key"
+      end
+      define_method("#{flag}?") { Bundler.settings[flag] }
+    end
+
+    (1..10).each {|v| define_method("bundler_#{v}_mode?") { major_version >= v } }
+
+    settings_flag :allow_offline_install
+    settings_flag :plugins
+
+    def initialize(bundler_version)
+      @bundler_version = Gem::Version.create(bundler_version)
+    end
+
+    def major_version
+      @bundler_version.segments.first
+    end
+    private :major_version
+
+    class << self; private :settings_flag; end
+  end
+end
diff --git a/lib/bundler/fetcher/compact_index.rb b/lib/bundler/fetcher/compact_index.rb
index fb77451822..9461368df5 100644
--- a/lib/bundler/fetcher/compact_index.rb
+++ b/lib/bundler/fetcher/compact_index.rb
@@ -110,7 +110,7 @@ module Bundler
           begin
             downloader.fetch(fetch_uri + path, headers)
           rescue NetworkDownError => e
-            raise unless Bundler.settings[:allow_offline_install] && headers["If-None-Match"]
+            raise unless Bundler.feature_flag.allow_offline_install? && headers["If-None-Match"]
             Bundler.ui.warn "Using the cached data for the new index because of a network error: #{e}"
             Net::HTTPNotModified.new(nil, nil, nil)
           end
diff --git a/lib/bundler/inline.rb b/lib/bundler/inline.rb
index dcaf22944c..af542f1e44 100644
--- a/lib/bundler/inline.rb
+++ b/lib/bundler/inline.rb
@@ -41,7 +41,7 @@ def gemfile(install = false, options = {}, &gemfile)
   end
   ENV["BUNDLE_GEMFILE"] ||= "Gemfile"
 
-  Bundler::Plugin.gemfile_install(&gemfile) if Bundler.settings[:plugins]
+  Bundler::Plugin.gemfile_install(&gemfile) if Bundler.feature_flag.plugins?
   builder = Bundler::Dsl.new
   builder.instance_eval(&gemfile)
 
diff --git a/lib/bundler/plugin.rb b/lib/bundler/plugin.rb
index 1f0297f29b..015be99af8 100644
--- a/lib/bundler/plugin.rb
+++ b/lib/bundler/plugin.rb
@@ -158,7 +158,7 @@ module Bundler
     #
     # @param [String] event
     def hook(event, *args, &arg_blk)
-      return unless Bundler.settings[:plugins]
+      return unless Bundler.feature_flag.plugins?
 
       plugins = index.hook_plugins(event)
       return unless plugins.any?
diff --git a/lib/bundler/source/git.rb b/lib/bundler/source/git.rb
index 60fb555f0a..d1757a4a93 100644
--- a/lib/bundler/source/git.rb
+++ b/lib/bundler/source/git.rb
@@ -292,7 +292,7 @@ module Bundler
       def fetch
         git_proxy.checkout
       rescue GitError
-        raise unless Bundler.settings[:allow_offline_install]
+        raise unless Bundler.feature_flag.allow_offline_install?
         Bundler.ui.warn "Using cached git data because of network errors"
       end
     end