Copyright 2019 The Go Authors. All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
Package descopts contains the nil pointers to concrete descriptor options. This package exists as a form of reverse dependency injection so that certain packages (e.g., internal/filedesc and internal/filetype can avoid a direct dependency on the descriptor proto package).
package descopts

import pref 
These variables are set by the init function in descriptor.pb.go via logic in internal/filetype. In other words, so long as the descriptor proto package is linked in, these variables will be populated. Each variable is populated with a nil pointer to the options struct.