protobufjs/ext/descriptor

Experimental extension for interoperability with descriptor.proto types.

Usage

var protobuf   = require("@apollo/protobufjs"), // requires the full library
    descriptor = require("@apollo/protobufjs/ext/descriptor");

var root = ...;

// convert any existing root instance to the corresponding descriptor type
var descriptorMsg = root.toDescriptor("proto2");
// ^ returns a FileDescriptorSet message, see table below

// encode to a descriptor buffer
var buffer = descriptor.FileDescriptorSet.encode(descriptorMsg).finish();

// decode from a descriptor buffer
var decodedDescriptor = descriptor.FileDescriptorSet.decode(buffer);

// convert any existing descriptor to a root instance
root = protobuf.Root.fromDescriptor(decodedDescriptor);
// ^ expects a FileDescriptorSet message or buffer, see table below

// and start all over again

API

The extension adds .fromDescriptor(descriptor[, syntax]) and #toDescriptor([syntax]) methods to reflection objects and exports the .google.protobuf namespace of the internally used Root instance containing the following types present in descriptor.proto:

Descriptor type	protobuf.js type	Remarks
FileDescriptorSet	Root
FileDescriptorProto		dependencies are not supported
FileOptions
FileOptionsOptimizeMode
SourceCodeInfo		not supported
SourceCodeInfoLocation
GeneratedCodeInfo		not supported
GeneratedCodeInfoAnnotation
DescriptorProto	Type
MessageOptions
DescriptorProtoExtensionRange
DescriptorProtoReservedRange
FieldDescriptorProto	Field
FieldDescriptorProtoLabel
FieldDescriptorProtoType
FieldOptions
FieldOptionsCType
FieldOptionsJSType
OneofDescriptorProto	OneOf
OneofOptions
EnumDescriptorProto	Enum
EnumOptions
EnumValueDescriptorProto
EnumValueOptions		not supported
ServiceDescriptorProto	Service
ServiceOptions
MethodDescriptorProto	Method
MethodOptions
UninterpretedOption		not supported
UninterpretedOptionNamePart

Note that not all features of descriptor.proto translate perfectly to a protobuf.js root instance. A root instance has only limited knowlege of packages or individual files for example, which is then compensated by guessing and generating fictional file names.

When using TypeScript, the respective interface types can be used to reference specific message instances (i.e. protobuf.Message<IDescriptorProto>).