Add a special bundler binstub that ensures the correct version is activated

2 files changed, 74 insertions, 0 deletions

diff --git a/lib/bundler/templates/Executable b/lib/bundler/templates/Executable
index 86e73fbbc3..9289debc26 100755
--- a/lib/bundler/templates/Executable
+++ b/lib/bundler/templates/Executable
@@ -8,6 +8,9 @@
 # this file is here to facilitate running it.
 #
 
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+load(bundle_binstub) if File.file?(bundle_binstub)
+
 require "pathname"
 ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../<%= relative_gemfile_path %>",
   Pathname.new(__FILE__).realpath)
diff --git a/lib/bundler/templates/Executable.bundler b/lib/bundler/templates/Executable.bundler
new file mode 100644
index 0000000000..351eca7427
--- /dev/null
+++ b/lib/bundler/templates/Executable.bundler
@@ -0,0 +1,71 @@
+#!/usr/bin/env <%= Bundler.settings[:shebang] || RbConfig::CONFIG["ruby_install_name"] %>
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application '<%= executable %>' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "rubygems"
+
+m = Module.new do
+  module_function
+
+  def env_var_version
+    ENV['BUNDLER_VERSION']
+  end
+
+  def cli_arg_version
+    update = "update".start_with?(ARGV.first || " ") && ARGV.find {|a| a.start_with?("--bundler") }
+    update &&= update =~ /--bundler(?:=(.+))?/ && $1 || "> 0.a"
+  end
+
+  def gemfile
+    gemfile = ENV['BUNDLE_GEMFILE']
+    return gemfile if gemfile && !gemfile.empty?
+
+    File.expand_path("../<%= relative_gemfile_path %>", __FILE__)
+  end
+
+  def lockfile
+    File.expand_path case File.basename(gemfile)
+                      when 'gems.rb' then gemfile.sub(/\.rb$/, gemfile)
+                      else "#{gemfile}.lock"
+                      end
+  end
+
+  def lockfile_version
+    return unless File.file?(lockfile)
+    lockfile_contents = File.read(lockfile)
+    return unless lockfile_contents =~ /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+    Regexp.last_match(1)
+  end
+
+  def bundler_version
+    @bundler_version ||= begin
+      env_var_version || cli_arg_version ||
+        lockfile_version || "#{Gem::Requirement.default}.a"
+    end
+  end
+
+  def load_bundler!
+    ENV["BUNDLE_GEMFILE"] ||= gemfile
+
+    activate_bundler(bundler_version)
+  end
+
+  def activate_bundler(bundler_version)
+    gem "bundler", bundler_version
+  rescue StandardError, LoadError => e
+    warn "Activating bundler (#{bundler_version}) failed:\n#{e.message}\n\nTo install the version of bundler this project requires, run `gem install bundler -v '#{bundler_version}'`"
+    exit 42
+  end
+end
+
+m.load_bundler!
+
+if File.expand_path($0) == File.expand_path(__FILE__)
+  load Gem.bin_path("<%= spec.name %>", "<%= executable %>")
+end