genswagger fails on Ubuntu on Windows (WSL): value of type genswagger.alias is not assignable to type genswagger.alias

[leonbloy]

I cannot make genswagger work on Ubuntu 18 on Windows (WSL1)

My setup:

$ uname -a
Linux DESKTOP-BGT2SIH 4.4.0-18362-Microsoft #476-Microsoft x86_64 x86_64 x86_64 GNU/Linux
$ go version
go version go1.10.3 gccgo (Ubuntu 8.3.0-6ubuntu1~18.04.1) 8.3.0 linux/amd64

I'm using protoc 3.0.0 from Ubuntu package protobuf-compiler 3.0.0-9.1ubuntu1 amd64
The same happens if I replace the binary (and the include files) from latest version 3.11.1

Tested with this sample.proto file

syntax = "proto3";

message SearchRequest {
  string query = 1;
  int32 page_number = 2;
  int32 result_per_page = 3;
}

message SearchResponse {
  repeated Result results = 1;
}

message Result {
  string url = 1;
  string title = 2;
  repeated string snippets = 3;
}

service SearchService {
  rpc Search (SearchRequest) returns (SearchResponse);
}

Generation works ok

$ protoc --go_out=. sample.proto

But the swagger generation fails systematically:

$ protoc --swagger_out=logtostderr=true:. -I. sample.proto
panic: reflect.Set: value of type genswagger.alias is not assignable to type genswagger.alias [recovered]
        panic: reflect.Set: value of type genswagger.alias is not assignable to type genswagger.alias [recovered]
        panic: reflect.Set: value of type genswagger.alias is not assignable to type genswagger.alias

goroutine 1 [running]:
panic
        ../../../src/libgo/go/runtime/panic.go:554
json.r
        ../../../src/libgo/go/encoding/json/encode.go:293
json.func1
        ../../../src/libgo/go/encoding/json/encode.go:287
panic
        ../../../src/libgo/go/runtime/panic.go:495
json.r
        ../../../src/libgo/go/encoding/json/encode.go:293
json.func1
        ../../../src/libgo/go/encoding/json/encode.go:287
panic
        ../../../src/libgo/go/runtime/panic.go:495
reflect.Value.assignTo
        ../../../src/libgo/go/reflect/value.go:2075
reflect.Value.Set
        ../../../src/libgo/go/reflect/value.go:1213
genswagger.extensionMarshalJSON
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:134
github_com_grpc_ecosystem_grpc_gateway_protoc_gen_swagger_genswagger.swaggerInfoObject.MarshalJSON
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:86
json.marshalerEncoder
        ../../../src/libgo/go/encoding/json/encode.go:445
encoding_json.structEncoder.encode
        ../../../src/libgo/go/encoding/json/encode.go:639
encoding_json.encodeState.reflectValue
        ../../../src/libgo/go/encoding/json/encode.go:325
encoding_json.encodeState.marshal
        ../../../src/libgo/go/encoding/json/encode.go:298
encoding_json.Marshal
        ../../../src/libgo/go/encoding/json/encode.go:161
genswagger.extensionMarshalJSON
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:138
github_com_grpc_ecosystem_grpc_gateway_protoc_gen_swagger_genswagger.swaggerObject.MarshalJSON
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:81
json.marshalerEncoder
        ../../../src/libgo/go/encoding/json/encode.go:445
encoding_json.encodeState.reflectValue
        ../../../src/libgo/go/encoding/json/encode.go:325
encoding_json.encodeState.marshal
        ../../../src/libgo/go/encoding/json/encode.go:298
encoding_json.Encoder.Encode
        ../../../src/libgo/go/encoding/json/stream.go:200
genswagger.encodeSwagger
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:146
github_com_grpc_ecosystem_grpc_gateway_protoc_gen_swagger_genswagger.generator.Generate
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/generator.go:212
main.main
        /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/main.go:119
--swagger_out: protoc-gen-swagger: Plugin failed with status code 2.

Using the latest go packages:

$ cd /home/hernan/go/src/github.com/grpc-ecosystem/grpc-gateway
/go/src/github.com/grpc-ecosystem/grpc-gateway$ git log
commit 3c06998610d4d2edea99d12228b1f6ea2d943ce4 (HEAD -> master, origin/master, origin/HEAD)
Author: Guilherme Santos <xguiga@gmail.com>
Date:   Tue Dec 3 18:02:09 2019 +0100

    Override operation_id when available
...

[johanbrandhorst]

Can you try upgrading your Go version? We only support Go 1.12 and 1.13 (those supported by the Go team).

[johanbrandhorst]

Also, I would recommend using the standard Go compiler, not gccgo. It can be installed from https://golang.org/dl/.

[leonbloy]

Problem solved after removing gccgo (I actually removed all go packages and reinstalled golang-go)

Currently working with golang-1.10-go

[johanbrandhorst]

Good to hear 👍