Track Bundler version in lockfile

lib/bundler/definition.rb

@@ -56,6 +56,7 @@ def initialize(lockfile, dependencies, sources, unlock, ruby_version = nil)
         @lockfile_contents = Bundler.read_file(lockfile)
         locked = LockfileParser.new(@lockfile_contents)
         @platforms      = locked.platforms
+        @locked_bundler_version = locked.bundler_version
 
         if unlock != true
           @locked_deps    = locked.dependencies
@@ -256,6 +257,16 @@ def lock(file)
         "#{File.expand_path(file)}"
     end
 
+    # Returns the version of Bundler that is creating or has created
+    # Gemfile.lock. Used in #to_lock.
+    def lock_version
+      if @locked_bundler_version && @locked_bundler_version < Gem::Version.new(Bundler::VERSION)
+        new_version = Bundler::VERSION
+      end
+
+      new_version || @locked_bundler_version || Bundler::VERSION
+    end
+
     def to_lock
       out = ""
 
@@ -294,6 +305,10 @@ def to_lock
           handled << dep.name
       end
 
+      # Record the version of Bundler that was used to create the lockfile
+      out << "\nBUNDLED WITH\n"
+      out << "  #{lock_version}\n"
+
       out
     end
 

lib/bundler/lockfile_parser.rb

@@ -12,8 +12,9 @@
 
 module Bundler
   class LockfileParser
-    attr_reader :sources, :dependencies, :specs, :platforms
+    attr_reader :sources, :dependencies, :specs, :platforms, :bundler_version
 
+    BUNDLED      = "BUNDLED WITH"
     DEPENDENCIES = "DEPENDENCIES"
     PLATFORMS    = "PLATFORMS"
     GIT          = "GIT"
@@ -41,18 +42,32 @@ def initialize(lockfile)
           @state = :dependency
         elsif line == PLATFORMS
           @state = :platform
+        elsif line == BUNDLED
+          @state = :bundled_with
         else
           send("parse_#{@state}", line)
         end
       end
       @sources << @rubygems_aggregate
       @specs = @specs.values
+      warn_for_outdated_bundler_version
     rescue ArgumentError => e
       Bundler.ui.debug(e)
       raise LockfileError, "Your lockfile is unreadable. Run `rm Gemfile.lock` " \
         "and then `bundle install` to generate a new lockfile."
     end
 
+    def warn_for_outdated_bundler_version
+      return unless bundler_version
+      prerelease_text = bundler_version.prerelease? ? " --pre" : ""
+      if Gem::Version.new(Bundler::VERSION) < Gem::Version.new(bundler_version)
+        Bundler.ui.warn "Warning: the running version of Bundler is older " \
+             "than the version that created the lockfile. We suggest you " \
+             "upgrade to the latest version of Bundler by running `gem " \
+             "install bundler#{prerelease_text}`.\n"
+      end
+    end
+
   private
 
     TYPES = {
@@ -157,5 +172,12 @@ def parse_platform(line)
       end
     end
 
+    def parse_bundled_with(line)
+      line = line.strip
+      if Gem::Version.correct?(line)
+        @bundler_version = Gem::Version.create(line)
+      end
+    end
+
   end
 end

spec/commands/lock_spec.rb

@@ -47,6 +47,9 @@ def read_lockfile(file = "Gemfile.lock")
         foo
         rails
         with_license
+
+      BUNDLED WITH
+        #{Bundler::VERSION}
     L
   end
 

spec/install/gems/flex_spec.rb

@@ -267,6 +267,9 @@
 
       DEPENDENCIES
         rack
+
+      BUNDLED WITH
+        #{Bundler::VERSION}
       L
     end
   end