Variable import order caused by "option go_package" in conjunction with "import"

[ashleyvega]

When one or both of the option go_package lines in the below 2 files are enabled, the import order changes randomly between:

	_ "." // or "github.com/someuser/api_a"
	_ "github.com/mwitkow/go-proto-validators"

and vice versa.

File: a.proto

syntax = "proto3";
package a;
// option go_package = "github.com/someuser/api_a";
message Thing { string id = 1; }

File: b.proto

syntax = "proto3";
import "a.proto";
package b;
// option go_package = "github.com/someuser/api_b";
import "github.com/mwitkow/go-proto-validators/validator.proto";
message SomethingContainingThing { a.Thing thing = 1 [(validator.field) = {msg_exists : true}]; }

Makefile

default: b.validator.pb.go b.pb.go

%.validator.pb.go: %.proto a.proto
	@protoc -I. -Ivendor -Ivendor/github.com/protocolbuffers/protobuf/src --govalidators_out=paths=source_relative:. "$<"

%.pb.go: %.proto a.proto
	@protoc -I. -Ivendor -Ivendor/github.com/protocolbuffers/protobuf/src --go_out=paths=source_relative:. "$<"

.PHONY: clean
clean:
	@rm -f *.pb.go

Script to highlight flake

F="b.validator.pb.go"
while true ; do
    rm -f "$F"
    make "$F"
    md5="$(md5sum "$F" | awk '{print $1}')"
    echo -e "$(date)\t$md5"
    mv "$F "$md5-$F"
done

(If F is changed to b.pb.go, no flakiness is observed in the output.)

In the vendor dir we have:

tree -d vendor
vendor/
└── github.com
    ├── google
    │   └── protobuf
    │       └── src
    │           └── google
    │               └── protobuf
    │                   ├── compiler
    │                   │   ├── cpp
    │                   │   └── ruby
    │                   └── util
    │                       └── internal
    │                           └── testdata
    └── mwitkow
        └── go-proto-validators
            ├── examples
            └── test

Versions:

• mwitkow/go-proto-validators is at 1f38828 (28/Mar/2019)
• protocolbuffers/protobuf is at f425b9f (12/Feb/2019, or v3.7.0+incompatible according to go.mod)

[zifter]

Fix here gogo/protobuf#700