Auto merge of #5327 - bundler:seg-outdated-bundler-message, r=indirect

[CLI] Warn when running an outdated bundler version

Closes https://github.com/bundler/bundler/issues/4683.

The `send`s are super hacky but ¯\_(ツ)_/¯

2 files changed, 24 insertions, 1 deletions

diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index eb9362a5..a70d66f2 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -13,6 +13,7 @@ module Bundler
       Bundler.ui = UI::Shell.new
       raise e
     ensure
+      warn_on_outdated_bundler
       Bundler::SharedHelpers.print_major_deprecations!
     end
 
@@ -579,5 +580,26 @@ module Bundler
       command.reject!(&:empty?)
       Bundler.ui.info "Running `#{command * " "}` with bundler #{Bundler::VERSION}"
     end
+
+    def self.warn_on_outdated_bundler
+      return if Bundler.settings[:disable_version_check]
+
+      latest = Fetcher::CompactIndex.
+               new(nil, Source::Rubygems::Remote.new(URI("https://rubygems.org")), nil).
+               send(:compact_index_client).
+               instance_variable_get(:@cache).
+               dependencies("bundler").
+               map {|d| Gem::Version.new(d.first) }.
+               max
+      return unless latest
+
+      current = Gem::Version.new(VERSION)
+      return if current >= latest
+
+      Bundler.ui.warn "The latest bundler is #{latest}, but you are currently running #{current}.\nTo update, run `gem install bundler#{" --pre" if latest.prerelease?}`"
+    rescue
+      nil
+    end
+    private_class_method :warn_on_outdated_bundler
   end
 end
diff --git a/lib/bundler/settings.rb b/lib/bundler/settings.rb
index 35ad17ae..b2136384 100644
--- a/lib/bundler/settings.rb
+++ b/lib/bundler/settings.rb
@@ -11,6 +11,8 @@ module Bundler
       disable_exec_load
       disable_local_branch_check
       disable_shared_gems
+      disable_version_check
+      force_ruby_platform
       frozen
       gem.coc
       gem.mit
@@ -18,7 +20,6 @@ module Bundler
       major_deprecations
       no_install
       no_prune
-      force_ruby_platform
       only_update_to_newer_versions
       plugins
       silence_root_warning