Imports are confusing

I have a gRPC client that is trying to import a service and no matter what I try it does not get around the problem. Seems that importing for gRPC has some hidden naming rules which are not spelled out in the example I have seen.

 cargo build
   Compiling client v0.1.0 (/Users/bihaber/projects/rust/helloworld/helloworld/client)
error[E0432]: unresolved import `self::IMService::IMService_client`
 --> src/
3 | use self::IMService::{HelloRequest, IMService_client::HelloClient};
  |                                     ^^^^^^^^^^^^^^^^ could not find `IMService_client` in `IMService`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `client` (bin "client") due to previous error

Protobuf look like -

syntax = "proto3";
package hello;

// The greeting service definition.
service IMService {
  // This is the description for the grpc SayHello Greeter Service. This takes in a HelloRequest as message and returns
  // a HelloReply greeting message. Used to Send a greeting.
  rpc SayHello (HelloRequest) returns (HelloReply) {}

// The request message containing the user's name.
message HelloRequest {
  // This is the description for the name attribute of the HelloRequest message.
  string name = 1;
  string pass = 2;

// The response message containing the greetings
message HelloReply {
  // This is the description for the message attribute of the HelloReply message.
  string message = 1;
  string token = 2;

Assuming you’re using the tonic crate to do this, it looks like the submodule name is generated by this function, so you’re probably looking for something like this:

use self::IMService::i_m_service_client::IMServiceClient;

Simplifying down to just the problematic import, we have:

use self::IMService::IMService_client::HelloClient;

This appears in src/ self in this context is the top-level module for the crate - the module defined either by if this is a library crate, or by if this is a binary crate, assuming Cargo's defaults apply.

That means that, for this import to resolve, that crate needs to contain a namespace named IMService (probably as a module), which in turn needs to contain an IMService_client namespace (ditto), which in turn exposes a symbol HelloClient. The error points to that second step: IMService does exists, but whatever it is, it doesn't contain IMService_client.

If these are all expected to be modules, where is IMService defined?

If the answer is "mod IMService; in or in," does the file src/ exist?

If the answer to the above is yes, does that file include a declaration for the symbol IMService_client (for example via a mod or pub use statement, or by defining a type, function, trait, or similar)?

1 Like

There is no src/ Everything is in the src/ I suspect there is a naming issue with gRPC. I have tried many ways to get around the problem and the only thing that seems to work is making everything a single word in lower case. But other problems prevent the program from working.

Error: Status { code: Unimplemented, message: "Method not found: imserver.imserver/hello", metadata: MetadataMap { headers: {"content-type": "application/grpc"} }, source: None }
And yes I had to jerk around the names to get it to build and run. This error doesn't make sense as everything matches the proto.

as everything matches the proto.

i haven't used tonic or gRPC in Rust, but i have tiny experience with gRPC in python.

I assume process is similar to other languages -> so your protofile with name XXX.proto should "translate" to a newly generated (plus some naming case conversions possibly) after bubbling through tonic_build crate as part of a build process? Is my assumption that XXX = "IMService_client" correct?

could be hard to narrow down problem as we dont know wheter/how you deviated for standard workflow...
assuming you cannot share full project on online repo, maybe try adding here:

  • output of tree bash command - to show project structure of relevant files, primarily including

    • location of .proto
    • file that has problematic "uses" statement
    • whole chain of parent modules/folders up to cargo root directory
  • steps that you had to take in so called jerking and maybe an error tha lead you to it

This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.