1 files changed, 49 insertions, 0 deletions
diff --git a/lib/rubygems/source/lock.rb b/lib/rubygems/source/lock.rb
new file mode 100644
index 0000000000..70849210bd
--- /dev/null
+++ b/lib/rubygems/source/lock.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+##
+# A Lock source wraps an installed gem's source and sorts before other sources
+# during dependency resolution.  This allows RubyGems to prefer gems from
+# dependency lock files.
+
+class Gem::Source::Lock < Gem::Source
+  ##
+  # The wrapped Gem::Source
+
+  attr_reader :wrapped
+
+  ##
+  # Creates a new Lock source that wraps +source+ and moves it earlier in the
+  # sort list.
+
+  def initialize(source)
+    @wrapped = source
+  end
+
+  def <=>(other) # :nodoc:
+    case other
+    when Gem::Source::Lock then
+      @wrapped <=> other.wrapped
+    when Gem::Source then
+      1
+    end
+  end
+
+  def ==(other) # :nodoc:
+    (self <=> other) == 0
+  end
+
+  def hash # :nodoc:
+    @wrapped.hash ^ 3
+  end
+
+  ##
+  # Delegates to the wrapped source's fetch_spec method.
+
+  def fetch_spec(name_tuple)
+    @wrapped.fetch_spec name_tuple
+  end
+
+  def uri # :nodoc:
+    @wrapped.uri
+  end
+end