Service reflection can not handle directory paths with imported proto files

[nkoson]

What version of gRPC are you using?

1.63.2

What version of Go are you using (go version)?

1.21.0

What operating system (Linux, Windows, …) and version?

macOS 13.2

What did you do?

My proto file
api/proto/services/foo/v1/foo.proto

imports a file from another directory:
import "api/proto/v1/bar.proto";

and I instruct protoc with
-I ./

start the gRPC server and describe its services with grpcurl:

grpcurl -plaintext -use-reflection localhost:8888 describe

File not found: api/proto/v1/bar.proto

(for the record, the issue persists in Postman as well)

However, if I change the import in api/proto/services/foo/v1/foo.proto to
import "bar.proto";

and instruct protoc with
-I ./api/proto/v1

then service reflection works fine.

What did you expect to see?

Service reflection should be able to traverse directories.

What did you see instead?

Service reflection only working when the import statement does not describe a directory path.