[ParallelInstaller] Do not deadlock when the lockfile is missing depe…

…ndencies entirely

lib/bundler/installer/parallel_installer.rb

@@ -71,6 +71,10 @@ def all_dependencies
       def to_s
         "#<#{self.class} #{@spec.full_name} (#{state})>"
       end
+
+      def full_name
+        @spec.full_name
+      end
     end
 
     def self.call(*args)
@@ -164,7 +168,11 @@ def check_for_corrupt_lockfile
         warning << "* #{missing.map(&:name).join(", ")} depended upon by #{spec.name}"
       end
 
-      Bundler.ui.warn(warning.join("\n"))
+      warning = warning.join("\n")
+
+      fatally_missing_specs = missing_dependencies.map(&:last).flatten.map(&:name) - @specs.map(&:name)
+      return Bundler.ui.warning(warning) if fatally_missing_specs.empty?
+      raise InstallError, warning.concat("\n\nBundler is unable to continue installing without #{fatal.join(",")} in the lockfile.")
     end
 
     def require_tree_for_spec(spec)

spec/lock/lockfile_spec.rb

@@ -1258,6 +1258,35 @@
     L
   end
 
+  it "does not deadlock when the lockfile is missing dependencies entirely" do
+    lockfile <<-L
+      GEM
+        remote: file:#{gem_repo1}/
+        specs:
+          thin (1.0)
+
+      PLATFORMS
+        ruby
+
+      DEPENDENCIES
+        thin
+    L
+
+    install_gemfile <<-G
+      source "file://#{gem_repo1}"
+      gem "thin"
+    G
+
+    expect(out).to end_with(<<-S.strip)
+Your lockfile was created by an old Bundler that left some things out.
+You can fix this by adding the missing gems to your Gemfile, running bundle install, and then removing the gems from your Gemfile.
+The missing gems are:
+* rack depended upon by thin
+
+Bundler is unable to continue installing without rack in the lockfile.
+    S
+  end
+
   describe "a line ending" do
     def set_lockfile_mtime_to_known_value
       time = Time.local(2000, 1, 1, 0, 0, 0)