Passing ENUM value as URL parameter throws error

[igateno]

I'm having issues passing an ENUM values as a URL parameter.

For example, this works just fine: /v0/tickets?id=1

But I have if I have an enum Priority like this:

  enum Priority {
    UNDEFINED = 0;
    LOW = 1;
    MEDIUM = 2;
    HIGH = 3;
    CRITICAL = 4;
  }

Neither /v0/tickets?priority=HIGH or /v0/tickets?priority=3 work for me.

The former returns:

400 Bad Request

{
  "Error": "strconv.ParseInt: parsing \"HIGH\": invalid syntax",
  "Code": 3
}

And the latter crashes my gateway server with this stacktrace:

Server listening on port 9090
2016/05/23 11:19:56 http: panic serving [::1]:50880: reflect.Set: value of type int32 is not assignable to type workflow.Ticket_Priority
goroutine 24 [running]:
net/http.(*conn).serve.func1(0xc82016a280)
        /usr/local/go/src/net/http/server.go:1389 +0xc1
panic(0x408820, 0xc820064ca0)
        /usr/local/go/src/runtime/panic.go:426 +0x4e9
reflect.Value.assignTo(0x4045a0, 0xc8200699c0, 0x85, 0x5a9d30, 0xb, 0x4e9540, 0x0, 0x0, 0x0, 0x0)
        /usr/local/go/src/reflect/value.go:2164 +0x3be
reflect.Value.Set(0x4e9540, 0xc8201e00f0, 0x185, 0x4045a0, 0xc8200699c0, 0x85)
        /usr/local/go/src/reflect/value.go:1334 +0x95
github.com/gengo/grpc-gateway/runtime.populateField(0x4e9540, 0xc8201e00f0, 0x185, 0xc8200696a1, 0x1, 0x0, 0x0)
        /Users/isaac/dev/gopath/src/github.com/gengo/grpc-gateway/runtime/query.go:124 +0x468
github.com/gengo/grpc-gateway/runtime.populateFieldValueFromPath(0x997a10, 0xc8200649d0, 0xc8200787a0, 0x2, 0x2, 0xc8200649f0, 0x1, 0x1, 0x0, 0x0)
        /Users/isaac/dev/gopath/src/github.com/gengo/grpc-gateway/runtime/query.go:83 +0x913
github.com/gengo/grpc-gateway/runtime.PopulateQueryParameters(0x997a10, 0xc8200649d0, 0xc8200697a0, 0x84c200, 0x0, 0x0)
        /Users/isaac/dev/gopath/src/github.com/gengo/grpc-gateway/runtime/query.go:22 +0x207
github.com/my-awesome-api/workflow.request_Workflow_ListTickets_0(0x997bd0, 0xc82006ce80, 0x997c10, 0x8412a0, 0x997d70, 0xc82002e218, 0xc82017e0e0, 0xc820069740, 0x0, 0x0, ...)
        /Users/isaac/dev/gopath/src/github.com/my-awesome-api/workflow/workflow.pb.gw.go:38 +0x100
github.com/my-awesome-api/workflow.RegisterWorkflowHandler.func1(0xe04630, 0xc82006b450, 0xc82017e0e0, 0xc820069740)
        /Users/isaac/dev/gopath/src/github.com/my-awesome-api/workflow/workflow.pb.gw.go:404 +0x28c
github.com/gengo/grpc-gateway/runtime.(*ServeMux).ServeHTTP(0xc820184d50, 0xe04630, 0xc82006b450, 0xc82017e0e0)
        /Users/isaac/dev/gopath/src/github.com/gengo/grpc-gateway/runtime/mux.go:89 +0xc52
net/http.serverHandler.ServeHTTP(0xc820166d00, 0xe04630, 0xc82006b450, 0xc82017e0e0)
        /usr/local/go/src/net/http/server.go:2081 +0x19e
net/http.(*conn).serve(0xc82016a280)
        /usr/local/go/src/net/http/server.go:1472 +0xf2e
created by net/http.(*Server).Serve
        /usr/local/go/src/net/http/server.go:2137 +0x44e

[igateno]

I guess I didn't read far enough into the README before posting this.

Any general guidance for someone who might try to dive in and implement the solution?

[buckhx]

You'd want to add a method that accepts an enum def to the runtime package in convert.go https://github.com/gengo/grpc-gateway/blob/master/runtime/convert.go

and add it to the proto3ConvertFuncs (& proto2) map https://github.com/gengo/grpc-gateway/blob/master/protoc-gen-grpc-gateway/descriptor/types.go#L293

which gets used by Parameter.ConvertFuncExpr() https://github.com/gengo/grpc-gateway/blob/master/protoc-gen-grpc-gateway/descriptor/types.go#L190

and is eventually rendered here in the template https://github.com/gengo/grpc-gateway/blob/master/protoc-gen-grpc-gateway/gengateway/template.go#L210

[tzneal]

The below change at least enables /v0/tickets?priority=3, though there's no range checking. I'll submit a PR if it's an acceptable interim solution until someone really fixes it.

diff --git a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/query.go b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/query.go
index 56a919a..a9102b5 100644
--- a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/query.go
+++ b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/query.go
@@ -121,7 +121,7 @@ func populateField(f reflect.Value, value string) error {
        if err := result[1].Interface(); err != nil {
                return err.(error)
        }
-       f.Set(result[0])
+       f.Set(result[0].Convert(f.Type()))
        return nil
 }