lib/plugin.proto

// Copyright 2009 Google Inc.  All rights reserved.
// Author: kenton@google.com (Kenton Varda)
//
// WARNING:  The plugin interface is currently EXPERIMENTAL and is subject to
//   change.
//
// protoc (aka the Protocol Compiler) can be extended via plugins.  A plugin is
// just a program that reads a CodeGeneratorRequest from stdin and writes a
// CodeGeneratorResponse to stdout.
//
// Plugins written using C++ can use net/proto2/compiler/public/plugin.h instead
// of dealing with the raw protocol defined here.
//
// A plugin executable needs only to be placed somewhere in the path.  The
// plugin should be named "protoc-gen-$NAME", and will then be used when the
// flag "--${NAME}_out" is passed to protoc.

syntax = "proto2";
package proto2.compiler;

import "descriptor.proto";

// An encoded CodeGeneratorRequest is written to the plugin's stdin.
message CodeGeneratorRequest {
  // The .proto files that were explicitly listed on the command-line.  The
  // code generator should generate code only for these files.  Each file's
  // descriptor will be included in proto_file, below.
  repeated string file_to_generate = 1;

  // The generator parameter passed on the command-line.
  optional string parameter = 2;

  // FileDescriptorProtos for all files in files_to_generate and everything
  // they import.  The files will appear in topological order, so each file
  // appears before any file that imports it.
  //
  // protoc guarantees that all proto_files will be written after
  // the fields above, even though this is not technically guaranteed by the
  // protobuf wire format.  This theoretically could allow a plugin to stream
  // in the FileDescriptorProtos and handle them one by one rather than read
  // the entire set into memory at once.  However, as of this writing, this
  // is not similarly optimized on protoc's end -- it will store all fields in
  // memory at once before sending them to the plugin.
  repeated FileDescriptorProto proto_file = 15;
}

// The plugin writes an encoded CodeGeneratorResponse to stdout.
message CodeGeneratorResponse {
  // Error message.  If non-empty, code generation failed.  The plugin process
  // should exit with status code zero even if it reports an error in this way.
  //
  // This should be used to indicate errors in .proto files which prevent the
  // code generator from generating correct code.  Errors which indicate a
  // problem in protoc itself -- such as the input CodeGeneratorRequest being
  // unparseable -- should be reported by writing a message to stderr and
  // exiting with a non-zero status code.
  optional string error = 1;

  // Represents a single generated file.
  message File {
    // The file name, relative to the output directory.  The name must not
    // contain "." or ".." components and must be relative, not be absolute (so,
    // the file cannot lie outside the output directory).  "/" must be used as
    // the path separator, not "\".
    //
    // If the name is omitted, the content will be appended to the previous
    // file.  This allows the generator to break large files into small chunks,
    // and allows the generated text to be streamed back to protoc so that large
    // files need not reside completely in memory at one time.  Note that as of
    // this writing protoc does not optimize for this -- it will read the entire
    // CodeGeneratorResponse before writing files to disk.
    optional string name = 1;

    // If non-empty, indicates that the named file should already exist, and the
    // content here is to be inserted into that file at a defined insertion
    // point.  This feature allows a code generator to extend the output
    // produced by another code generator.  The original generator may provide
    // insertion points by placing special annotations in the file that look
    // like:
    //   @@protoc_insertion_point(NAME)
    // The annotation can have arbitrary text before and after it on the line,
    // which allows it to be placed in a comment.  NAME should be replaced with
    // an identifier naming the point -- this is what other generators will use
    // as the insertion_point.  Code inserted at this point will be placed
    // immediately above the line containing the insertion point (thus multiple
    // insertions to the same point will come out in the order they were added).
    // The double-@ is intended to make it unlikely that the generated code
    // could contain things that look like insertion points by accident.
    //
    // For example, the C++ code generator places the following line in the
    // .pb.h files that it generates:
    //   // @@protoc_insertion_point(namespace_scope)
    // This line appears within the scope of the file's package namespace, but
    // outside of any particular class.  Another plugin can then specify the
    // insertion_point "namespace_scope" to generate additional classes or
    // other declarations that should be placed in this scope.
    //
    // Note that if the line containing the insertion point begins with
    // whitespace, the same whitespace will be added to every line of the
    // inserted text.  This is useful for languages like Python, where
    // indentation matters.  In these languages, the insertion point comment
    // should be indented the same amount as any inserted code will need to be
    // in order to work correctly in that context.
    //
    // The code generator that generates the initial file and the one which
    // inserts into it must both run as part of a single invocation of protoc.
    // Code generators are executed in the order in which they appear on the
    // command line.
    //
    // If |insertion_point| is present, |name| must also be present.
    optional string insertion_point = 2;

    // The file contents.
    optional string content = 15;
  }
  repeated File file = 15;
}