mirror of
https://github.com/gusaul/grpcox.git
synced 2024-11-17 14:56:26 +00:00
42 lines
2.4 KiB
Go
42 lines
2.4 KiB
Go
|
// Package desc contains "rich descriptors" for protocol buffers. The built-in
|
||
|
|
// descriptor types are simple protobuf messages, each one representing a
|
||
|
|
// different kind of element in the AST of a .proto source file.
|
||
|
|
//
|
||
|
|
// Because of this inherent "tree" quality, these build-in descriptors cannot
|
||
|
|
// refer to their enclosing file descriptor. Nor can a field descriptor refer to
|
||
|
|
// a message or enum descriptor that represents the field's type (for enum and
|
||
|
|
// nested message fields). All such links must instead be stringly typed. This
|
||
|
|
// limitation makes them much harder to use for doing interesting things with
|
||
|
|
// reflection.
|
||
|
|
//
|
||
|
|
// Without this package, resolving references to types is particularly complex.
|
||
|
|
// For example, resolving a field's type, the message type an extension extends,
|
||
|
|
// or the request and response types of an RPC method all require searching
|
||
|
|
// through symbols defined not only in the file in which these elements are
|
||
|
|
// declared but also in its transitive closure of dependencies.
|
||
|
|
//
|
||
|
|
// "Rich descriptors" avoid the need to deal with the complexities described
|
||
|
|
// above. A rich descriptor has all type references resolved and provides
|
||
|
|
// methods to access other rich descriptors for all referenced elements. Each
|
||
|
|
// rich descriptor has a usefully broad API, but does not try to mimic the full
|
||
|
|
// interface of the underlying descriptor proto. Instead, every rich descriptor
|
||
|
|
// provides access to that underlying proto, for extracting descriptor
|
||
|
|
// properties that are not immediately accessible through rich descriptor's
|
||
|
|
// methods.
|
||
|
|
//
|
||
|
|
// Rich descriptors can be accessed in similar ways as their "poor" cousins
|
||
|
|
// (descriptor protos). Instead of using proto.FileDescriptor, use
|
||
|
|
// desc.LoadFileDescriptor. Message descriptors and extension field descriptors
|
||
|
|
// can also be easily accessed using desc.LoadMessageDescriptor and
|
||
|
|
// desc.LoadFieldDescriptorForExtension, respectively.
|
||
|
|
//
|
||
|
|
// It is also possible create rich descriptors for proto messages that a given
|
||
|
|
// Go program doesn't even know about. For example, they could be loaded from a
|
||
|
|
// FileDescriptorSet file (which can be generated by protoc) or loaded from a
|
||
|
|
// server. This enables interesting things like dynamic clients: where a Go
|
||
|
|
// program can be an RPC client of a service it wasn't compiled to know about.
|
||
|
|
//
|
||
|
|
// Also see the grpcreflect, dynamic, and grpcdynamic packages in this same
|
||
|
|
// repo to see just how useful rich descriptors really are.
|
||
|
|
package desc
|