1 files changed, 109 insertions, 0 deletions
diff --git a/lib/rubygems/commands/lock_command.rb b/lib/rubygems/commands/lock_command.rb
new file mode 100644
index 0000000000..f7fd5ada16
--- /dev/null
+++ b/lib/rubygems/commands/lock_command.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require_relative "../command"
+
+class Gem::Commands::LockCommand < Gem::Command
+  def initialize
+    super "lock", "Generate a lockdown list of gems",
+          strict: false
+
+    add_option "-s", "--[no-]strict",
+               "fail if unable to satisfy a dependency" do |strict, options|
+      options[:strict] = strict
+    end
+  end
+
+  def arguments # :nodoc:
+    "GEMNAME       name of gem to lock\nVERSION       version of gem to lock"
+  end
+
+  def defaults_str # :nodoc:
+    "--no-strict"
+  end
+
+  def description # :nodoc:
+    <<-EOF
+The lock command will generate a list of +gem+ statements that will lock down
+the versions for the gem given in the command line.  It will specify exact
+versions in the requirements list to ensure that the gems loaded will always
+be consistent.  A full recursive search of all effected gems will be
+generated.
+
+Example:
+
+  gem lock rails-1.0.0 > lockdown.rb
+
+will produce in lockdown.rb:
+
+  require "rubygems"
+  gem 'rails', '= 1.0.0'
+  gem 'rake', '= 0.7.0.1'
+  gem 'activesupport', '= 1.2.5'
+  gem 'activerecord', '= 1.13.2'
+  gem 'actionpack', '= 1.11.2'
+  gem 'actionmailer', '= 1.1.5'
+  gem 'actionwebservice', '= 1.0.0'
+
+Just load lockdown.rb from your application to ensure that the current
+versions are loaded.  Make sure that lockdown.rb is loaded *before* any
+other require statements.
+
+Notice that rails 1.0.0 only requires that rake 0.6.2 or better be used.
+Rake-0.7.0.1 is the most recent version installed that satisfies that, so we
+lock it down to the exact version.
+    EOF
+  end
+
+  def usage # :nodoc:
+    "#{program_name} GEMNAME-VERSION [GEMNAME-VERSION ...]"
+  end
+
+  def complain(message)
+    if options[:strict]
+      raise Gem::Exception, message
+    else
+      say "# #{message}"
+    end
+  end
+
+  def execute
+    say "require 'rubygems'"
+
+    locked = {}
+
+    pending = options[:args]
+
+    until pending.empty? do
+      full_name = pending.shift
+
+      spec = Gem::Specification.load spec_path(full_name)
+
+      if spec.nil?
+        complain "Could not find gem #{full_name}, try using the full name"
+        next
+      end
+
+      say "gem '#{spec.name}', '= #{spec.version}'" unless locked[spec.name]
+      locked[spec.name] = true
+
+      spec.runtime_dependencies.each do |dep|
+        next if locked[dep.name]
+        candidates = dep.matching_specs
+
+        if candidates.empty?
+          complain "Unable to satisfy '#{dep}' from currently installed gems"
+        else
+          pending << candidates.last.full_name
+        end
+      end
+    end
+  end
+
+  def spec_path(gem_full_name)
+    gemspecs = Gem.path.map do |path|
+      File.join path, "specifications", "#{gem_full_name}.gemspec"
+    end
+
+    gemspecs.find {|path| File.exist? path }
+  end
+end