Auto merge of #4643 - bundler:seg-postit-trampoline, r=indirect

[bundle] Automatically trampoline to postit

- [x] Specs

~~Except on bundle exec, since that would be too slow~~

~~If you want, I guess we could vendor postit and manually setup the `LOAD_PATH` and `-r` the full path to the vendored postit exe. Your call.~~ Done this

\c @indirect

17 files changed, 341 insertions, 3 deletions

diff --git a/Rakefile b/Rakefile
index 43c5c58237..9bc34e4177 100644
--- a/Rakefile
+++ b/Rakefile
@@ -296,10 +296,21 @@ begin
     lib.prefix = "Bundler"
     lib.vendor_lib = "lib/bundler/vendor/thor"
   end
+
+  Automatiek::RakeTask.new("postit") do |lib|
+    lib.download = { :github => "https://github.com/bundler/postit" }
+    lib.namespace = "PostIt"
+    lib.vendor_lib = "lib/bundler/vendor/postit"
+
+    def lib.namespace_files
+      process_files(namespace, "BundlerVendoredPostIt")
+    end
+  end
 rescue LoadError
   namespace :vendor do
     task(:molinillo) { abort "Install the automatiek gem to be able to vendor gems." }
     task(:thor) { abort "Install the automatiek gem to be able to vendor gems." }
+    task(:postit) { abort "Install the automatiek gem to be able to vendor gems." }
   end
 end
 
diff --git a/exe/bundle b/exe/bundle
index 3fb4ccfce9..51a9035d97 100755
--- a/exe/bundle
+++ b/exe/bundle
@@ -4,6 +4,13 @@
 # Exit cleanly from an early interrupt
 Signal.trap("INT") { exit 1 }
 
+unless ENV["BUNDLE_DISABLE_POSTIT"]
+  update = "update".start_with?(ARGV.first || " ") && ARGV.find {|a| a.start_with?("--bundler") }
+  update &&= update =~ /--bundler(?:=(.+))?/ && $1 || "> 0.a"
+  ENV["BUNDLER_VERSION"] = update if update
+  require "bundler/postit_trampoline"
+end
+
 require "bundler"
 # Check if an older version of bundler is installed
 $LOAD_PATH.each do |path|
diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index 8585142352..c3a9a01e2b 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -204,6 +204,8 @@ module Bundler
       "Force downloading every gem."
     method_option "ruby", :type => :boolean, :banner =>
       "Update ruby specified in Gemfile.lock"
+    method_option "bundler", :type => :string, :lazy_default => "> 0.a", :banner =>
+      "Update the locked version of bundler"
     def update(*gems)
       require "bundler/cli/update"
       Update.new(options, gems).run
diff --git a/lib/bundler/cli/update.rb b/lib/bundler/cli/update.rb
index 037da2915e..33b0557fec 100644
--- a/lib/bundler/cli/update.rb
+++ b/lib/bundler/cli/update.rb
@@ -13,7 +13,7 @@ module Bundler
       sources = Array(options[:source])
       groups  = Array(options[:group]).map(&:to_sym)
 
-      if gems.empty? && sources.empty? && groups.empty? && !options[:ruby]
+      if gems.empty? && sources.empty? && groups.empty? && !options[:ruby] && !options[:bundler]
         # We're doing a full update
         Bundler.definition(true)
       else
diff --git a/lib/bundler/postit_trampoline.rb b/lib/bundler/postit_trampoline.rb
new file mode 100644
index 0000000000..7406612e5b
--- /dev/null
+++ b/lib/bundler/postit_trampoline.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+postit_lib = File.expand_path("../vendor/postit/lib", __FILE__)
+$:.unshift(postit_lib)
+require "postit"
+require "rubygems"
+
+environment = BundlerVendoredPostIt::Environment.new([])
+version = Gem::Requirement.new(environment.bundler_version)
+
+installed_version =
+  if defined?(Bundler::VERSION)
+    Bundler::VERSION
+  else
+    File.read(File.expand_path("../version.rb", __FILE__)) =~ /VERSION = "(.+)"/
+    $1
+  end
+installed_version &&= Gem::Version.new(installed_version)
+
+if !version.satisfied_by?(installed_version)
+  begin
+    installer = BundlerVendoredPostIt::Installer.new(version)
+    installer.install!
+  rescue => e
+    abort <<-EOS.strip
+Installing the inferred bundler version (#{version}) failed.
+If you'd like to update to the current bundler version (#{installed_version}) in this project, run `bundle update --bundler`.
+The error was: #{e}
+    EOS
+  end
+
+  Gem.loaded_specs.delete("bundler") unless defined?(Bundler)
+  gem "bundler", version
+  $:.delete(File.expand_path("../..", __FILE__))
+else
+  begin
+    gem "bundler", version
+  rescue LoadError
+    $:.unshift(File.expand_path("../..", __FILE__))
+  end
+end
+
+running_version = begin
+  require "bundler/version"
+  Bundler::VERSION
+rescue LoadError, NameError
+  nil
+end
+
+if !Gem::Version.correct?(running_version.to_s) || !version.satisfied_by?(Gem::Version.create(running_version))
+  abort "The running bundler (#{running_version}) does not match the required `#{version}`"
+end
+
+$:.delete_at($:.find_index(postit_lib))
diff --git a/lib/bundler/setup.rb b/lib/bundler/setup.rb
index 9aae6478cd..c888dabf2c 100644
--- a/lib/bundler/setup.rb
+++ b/lib/bundler/setup.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+require "bundler/postit_trampoline" unless ENV["BUNDLE_DISABLE_POSTIT"]
 require "bundler/shared_helpers"
 
 if Bundler::SharedHelpers.in_bundle?
diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index e21d616ecd..01f1118d7b 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -169,6 +169,7 @@ module Bundler
 
       # Set BUNDLE_GEMFILE
       ENV["BUNDLE_GEMFILE"] = find_gemfile.to_s
+      ENV["BUNDLER_VERSION"] = Bundler::VERSION
     end
 
     def set_path
diff --git a/lib/bundler/vendor/postit/lib/postit.rb b/lib/bundler/vendor/postit/lib/postit.rb
new file mode 100644
index 0000000000..4b3ff34d49
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit.rb
@@ -0,0 +1,15 @@
+require 'postit/environment'
+require 'postit/installer'
+require 'postit/parser'
+require 'postit/version'
+require 'rubygems'
+
+module BundlerVendoredPostIt
+  def self.setup
+    load File.expand_path('../postit/setup.rb', __FILE__)
+  end
+
+  def self.bundler_version
+    defined?(Bundler::VERSION) && Bundler::VERSION
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/environment.rb b/lib/bundler/vendor/postit/lib/postit/environment.rb
new file mode 100644
index 0000000000..b758fa0ccb
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/environment.rb
@@ -0,0 +1,44 @@
+require 'postit/parser'
+
+module BundlerVendoredPostIt
+  class Environment
+    def initialize(argv)
+      @argv = argv
+    end
+
+    def env_var_version
+      ENV['BUNDLER_VERSION']
+    end
+
+    def cli_arg_version
+      return unless str = @argv.first
+      str = str.dup.force_encoding('BINARY') if str.respond_to?(:force_encoding)
+      if Gem::Version.correct?(str)
+        @argv.shift
+        str
+      end
+    end
+
+    def gemfile
+      ENV['BUNDLE_GEMFILE'] || 'Gemfile'
+    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
+      BundlerVendoredPostIt::Parser.new(lockfile).parse
+    end
+
+    def bundler_version
+      @bundler_version ||= begin
+        env_var_version || cli_arg_version ||
+          lockfile_version || "#{Gem::Requirement.default}.a"
+      end
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/installer.rb b/lib/bundler/vendor/postit/lib/postit/installer.rb
new file mode 100644
index 0000000000..4139038df8
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/installer.rb
@@ -0,0 +1,28 @@
+module BundlerVendoredPostIt
+  class Installer
+    def initialize(bundler_version)
+      @bundler_version = bundler_version
+    end
+
+    def installed?
+      if Gem::Specification.respond_to?(:find_by_name)
+        !Gem::Specification.find_by_name('bundler', @bundler_version).nil?
+      else
+        requirement = Gem::Requirement.new(@bundler_version)
+        Gem.source_index.gems.values.any? do |s|
+          s.name == 'bundler' && requirement.satisfied_by?(s.version)
+        end
+      end
+    rescue LoadError
+      false
+    end
+
+    def install!
+      return if installed?
+      require 'rubygems/dependency_installer'
+      installer = Gem::DependencyInstaller.new
+      installer.install('bundler', @bundler_version)
+      installer.installed_gems
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/parser.rb b/lib/bundler/vendor/postit/lib/postit/parser.rb
new file mode 100644
index 0000000000..98c4a3578f
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/parser.rb
@@ -0,0 +1,21 @@
+require 'rubygems'
+
+module BundlerVendoredPostIt
+  class Parser
+    def initialize(file)
+      @file = file
+    end
+
+    BUNDLED_WITH =
+      /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+
+    def parse
+      return unless lockfile = File.file?(@file) && File.read(@file)
+      if lockfile =~ BUNDLED_WITH
+        Regexp.last_match(1)
+      else
+        '< 1.10'
+      end
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/setup.rb b/lib/bundler/vendor/postit/lib/postit/setup.rb
new file mode 100644
index 0000000000..260edd559d
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/setup.rb
@@ -0,0 +1,12 @@
+require 'postit/environment'
+require 'postit/installer'
+
+environment = BundlerVendoredPostIt::Environment.new(ARGV)
+version = environment.bundler_version
+
+installer = BundlerVendoredPostIt::Installer.new(version)
+installer.install!
+
+gem 'bundler', version
+
+require 'bundler/version'
diff --git a/lib/bundler/vendor/postit/lib/postit/version.rb b/lib/bundler/vendor/postit/lib/postit/version.rb
new file mode 100644
index 0000000000..1a16501024
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/version.rb
@@ -0,0 +1,3 @@
+module BundlerVendoredPostIt
+  VERSION = '0.1.2'.freeze
+end
diff --git a/spec/bundler/shared_helpers_spec.rb b/spec/bundler/shared_helpers_spec.rb
index 98f7994f9f..2ad0c98dba 100644
--- a/spec/bundler/shared_helpers_spec.rb
+++ b/spec/bundler/shared_helpers_spec.rb
@@ -222,7 +222,7 @@ describe Bundler::SharedHelpers do
     shared_examples_for "ENV['RUBYOPT'] gets set correctly" do
       it "ensures -rbundler/setup is at the beginning of ENV['RUBYOPT']" do
         subject.set_bundle_environment
-        expect(ENV["RUBYOPT"].split(" ").first).to include("-rbundler/setup")
+        expect(ENV["RUBYOPT"].split(" ")).to start_with("-rbundler/setup")
       end
     end
 
diff --git a/spec/other/trampoline_spec.rb b/spec/other/trampoline_spec.rb
new file mode 100644
index 0000000000..640c608508
--- /dev/null
+++ b/spec/other/trampoline_spec.rb
@@ -0,0 +1,137 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+describe "bundler version trampolining" do
+  before do
+    ENV["BUNDLE_DISABLE_POSTIT"] = nil
+    FileUtils.rm_rf(system_gem_path)
+    FileUtils.cp_r(base_system_gems, system_gem_path)
+  end
+
+  context "version guessing" do
+    shared_examples_for "guesses" do |version|
+      it "guesses the correct bundler version" do
+        bundle! "--version"
+        expect(out).to eq("Bundler version #{version}")
+
+        if bundled_app("Gemfile").file?
+          bundle! "exec ruby -e 'puts Bundler::VERSION'"
+          expect(out).to eq(version)
+        end
+      end
+    end
+
+    context "with a lockfile" do
+      before do
+        install_gemfile ""
+        lockfile lockfile.sub(Bundler::VERSION, "1.12.0")
+      end
+
+      include_examples "guesses", "1.12.0"
+    end
+
+    context "with BUNDLER_VERSION" do
+      before do
+        ENV["BUNDLER_VERSION"] = "1.12.0"
+      end
+
+      context "with a lockfile" do
+        before { install_gemfile "" }
+        include_examples "guesses", "1.12.0"
+      end
+
+      context "without a lockfile" do
+        include_examples "guesses", "1.12.0"
+      end
+    end
+
+    context "with no hints" do
+      include_examples "guesses", Bundler::VERSION
+    end
+
+    context "with a gemfile and no lockfile" do
+      before do
+        gemfile ""
+      end
+
+      include_examples "guesses", Bundler::VERSION
+    end
+  end
+
+  context "installing missing bundler versions", :realworld => true do
+    before do
+      ENV["BUNDLER_VERSION"] = "1.12.3"
+      if Bundler::RubygemsIntegration.provides?("< 2.6.4")
+        # necessary since we intall with 2.6.4 but the specs can run against
+        # older versions that match againt the "gem" invocation
+        %w(bundle bundler).each do |exe|
+          system_gem_path.join("bin", exe).open("a") do |f|
+            f << %(\ngem "bundler", ">= 0.a"\n)
+          end
+        end
+      end
+    end
+
+    it "guesses & installs the correct bundler version" do
+      expect(system_gem_path.join("gems", "bundler-1.12.3")).not_to exist
+      bundle! "--version"
+      expect(out).to eq("Bundler version 1.12.3")
+      expect(system_gem_path.join("gems", "bundler-1.12.3")).to exist
+    end
+
+    it "fails gracefully when installing the bundler fails" do
+      ENV["BUNDLER_VERSION"] = "9999"
+      bundle "--version", :expect_err => true
+      expect(err).to start_with(<<-E.strip)
+Installing the inferred bundler version (= 9999) failed.
+If you'd like to update to the current bundler version (1.12.5) in this project, run `bundle update --bundler`.
+The error was:
+      E
+    end
+  end
+
+  context "bundle update --bundler" do
+    before do
+      simulate_bundler_version("1.11.1") do
+        install_gemfile ""
+      end
+    end
+
+    it "updates to the specified version" do
+      # HACK: since no released bundler version actually supports this feature!
+      bundle "update --bundler=1.12.0", :expect_err => true
+      expect(out).to include("Unknown switches '--bundler=1.12.0'")
+    end
+
+    it "updates to the specified (running) version" do
+      # HACK: since no released bundler version actually supports this feature!
+      bundle! "update --bundler=#{Bundler::VERSION}"
+      bundle! "--version"
+      expect(out).to eq("Bundler version #{Bundler::VERSION}")
+    end
+
+    it "updates to the running version" do
+      # HACK: since no released bundler version actually supports this feature!
+      bundle! "update --bundler"
+      bundle! "--version"
+      expect(out).to eq("Bundler version #{Bundler::VERSION}")
+    end
+  end
+
+  context "-rbundler/setup" do
+    before do
+      simulate_bundler_version("1.12.0") do
+        install_gemfile ""
+      end
+    end
+
+    it "uses the locked version" do
+      ruby! <<-R
+        require "bundler/setup"
+        puts Bundler::VERSION
+      R
+      expect(err).to be_empty
+      expect(out).to eq("1.12.0")
+    end
+  end
+end
diff --git a/spec/support/helpers.rb b/spec/support/helpers.rb
index ff41dfbfa4..704e2140f5 100644
--- a/spec/support/helpers.rb
+++ b/spec/support/helpers.rb
@@ -12,6 +12,7 @@ module Spec
       end
       FileUtils.mkdir_p(tmp)
       FileUtils.mkdir_p(home)
+      ENV["BUNDLE_DISABLE_POSTIT"] = "1"
       Bundler.send(:remove_instance_variable, :@settings) if Bundler.send(:instance_variable_defined?, :@settings)
     end
 
diff --git a/spec/support/rubygems_ext.rb b/spec/support/rubygems_ext.rb
index 64cc41443d..95f596ea79 100644
--- a/spec/support/rubygems_ext.rb
+++ b/spec/support/rubygems_ext.rb
@@ -11,7 +11,8 @@ module Spec
         # Rake version has to be consistent for tests to pass
         "rake" => "10.0.2",
         # 3.0.0 breaks 1.9.2 specs
-        "builder" => "2.1.2"
+        "builder" => "2.1.2",
+        "bundler" => "1.12.0",
       }
       # ruby-graphviz is used by the viz tests
       deps["ruby-graphviz"] = nil if RUBY_VERSION >= "1.9.3"