Type-Registry for Go

Generates a type registry file based off of a set of types discovered during runtime, similar to go stringer. Used to generate a Map of names to reflect.Type from a Protobuf gRPC plugin.

How To Use

type-registry -in mytypes.pb.go

Scans mytypes.pb.go and writes out a map of name to each struct defined in that file, by default the output file is <inputfile>.typeregistry.go.

Options

• -in

  Input file to generate type registry from.

• -out

  Output file name; defaults to infile.typeregistry.go

• -package

  Package name to use in outfile; defaults to package name from infile.

• -registryfield

  Name of the field to declare the registry under; defaults to typeregistry

• -typenameprefix

  A prefix added to the type name values emitted.

  This feature allows generating the type registry of all the gRPC / protobuffer wrapper types. For example, we want to map a message of type Ping to the wrapper type GameMessage_Ping:

    typeregistry["Ping"] = reflect.TypeOf(GameMessage_Ping{})
  

  This requires using a typenameprefix of "GameMessage_".

  Note that this feature only generates type names that are valid structs contained within the infile: if GameMessage_Ping does not exist or is not a struct, "Ping" will be emitted instead:

        typeregistry["Ping"] = reflect.TypeOf(Ping{})
  

Example Usage

From command line, to take an input file from message.pb.go and create a registry mapping the structs in that file to their wrapper structs:

$ type-registry -in testdata/message.pb.go -typenameprefix GameMessage_

This creates an output file testdata/message.pb.typeregistry.go:

// Code generated by "type-registry -in ./message.pb.go -typenameprefix GameMessage_"; DO NOT EDIT.

package message

import "reflect"

var typeregistry = make(map[string]reflect.Type)


func init() {
	typeregistry["GameMessage_GetNotification"] = reflect.TypeOf(GameMessage_GetNotification{})
	typeregistry["DropRequest"] = reflect.TypeOf(GameMessage_DropRequest{})
	typeregistry["ErrorRequest"] = reflect.TypeOf(GameMessage_ErrorRequest{})
	typeregistry["ErrorResponse"] = reflect.TypeOf(GameMessage_ErrorResponse{})
	typeregistry["GetNotification"] = reflect.TypeOf(GameMessage_GetNotification{})
	typeregistry["GameMessage_LoginRequest"] = reflect.TypeOf(GameMessage_LoginRequest{})
	// etc. etc. etc.
}	

Using with go generate

This tool is meant to be used with go:generate for converting .proto files into .proto.go files, and then creating type registries of the structs found in that .proto.go file:

package message

//go:generate protoc -I . message.proto --go_out=plugins=grpc:.
//go:generate type-registry -in ./message.pb.go -typenameprefix GameMessage_

func BuildGameMessageUsingLotsOfReflection(payload interface{}) (result *GameMessage, err error) {
	// find the wrapper type for our payload
	wrapperType := typeregistry[reflect.TypeOf(payload).Name()]
	// do a bunch more stuff...
    return	
}