GH-585 Fix incomplete references to enums defined in separate packages

[elliotmjackson]

Generated Go code with references to enums from imported packages is broken. To fix this we recursively walk up the parents of the enum until it reaches the root file, prepending Message_ for each message it sees on the way. This builds up the generated enum type name.

resolves #586
resolves #624
resolves #604
resolves #626

Seems to be caused by an assumption in the go file template that assumes enums are defined under a message type.

Following is an _ variable that tries to make sure the import is used somewhere.

	{{ range $pkg, $path := enumPackages (externalEnums .) }}
		_ = {{ $pkg }}.{{ (index (externalEnums $) 0).Parent.Name }}_{{ (index (externalEnums $) 0).Name }}(0)
	{{ end }}

The Parent.Name_Name pattern is only valid in one case, when the enum is defined under a message. Any other place an enum can be defined will break, producing different kinds of failures.

Error case 1: Enum on its own

If the enum is on its own, the Parent is a file and you get something like

// pkg1/foo.proto
enum Enum { }

// pkg2/foo.proto
import "pkg1/foo.proto"

// pkg2/foo.pb.validate.go
_ = pkg1.pkg1/pkg1.proto_Enum(0)

This is not valid go code, and the GoFmt post-processor cannot format it correctly, hence the error.

EDIT: on closer thought, it looks valid (valid division), but it won't compile. I think it becomes invalid when a keyword like type appears as one of the path elements, since go will try and interpret it as a divisor.

Error case 2: enum is under a nested message (two messages deep)

OTOH, if the enum is defined under a nested message (message.message.enum), The Parent is just M2, however the enum type includes both M1 and M2 (type M1_M2_Enum). The result is you get a reference to something that does not exist.

// pkg1/foo.proto
message M1 { message M2 { enum Enum { } } }

// pkg2/foo.proto
import "pkg1/foo.proto"

// pkg2/foo.pb.validate.go
_ = pkg1.M2_Enum(0) // This does not exist, instead 'M1_M2_Enum(0)' is the correct value to use.

This causes code that generates successfully but will not compile.

[joshcarp]

end of day right now, will look at tomorrow

[danielbairstow97]

Is there any update on this fix? This issue has been plaguing me for the last couple weeks

[leefernandes]

huh, this is still borked

[elliotmjackson]

@leefernandes It's my understanding this is fixed BUT it has been "fixed" a few times now. Could you help me with the edge case you've found by example in a new issue?

[leefernandes]

@elliotmjackson Unfortunately I don't have the time to re-create a shareable representation of the proto files to share right now, but it occurred after migrating an enum to be an import. Prior to making the enum an import reference, the validation rule below worked.

	my.package.proto.v1.MyEnum my_enum = 8 [
		(google.api.field_behavior) = REQUIRED
		 // enum rule causes protoc validation error when referencing imported enum.
		 (validate.rules).enum = {
			defined_only: true,
			not_in: [0]
		}
	];

The error

pb.validate.go:154:14: undefined: v1

Here is our version of the lib.

    go_repository(
        name = "com_github_envoyproxy_protoc_gen_validate",
        build_file_proto_mode = "disable",
        importpath = "github.com/envoyproxy/protoc-gen-validate",
        sum = "h1:PS7VIOgmSVhWUEeZwTe7z7zouA22Cr590PzXKbZHOVY=",
        version = "v0.9.1",
    )