Important: This crate's functionality was incorporated into tonic-types and will be actively maintained there. This repository is no longer maintained.

Tonic Richer Error

Assets for implementation of the gRPC Richer Error Model with tonic.

This crate introduces the WithErrorDetails trait and implements it in tonic::Status, allowing the implementation of the gRPC Richer Error Model with tonic in a convenient way.

Examples | Website | Docs

Usage

The WithErrorDetails trait adds associated functions to tonic::Status that can be used on the server side to create a status with error details, that can then be returned to the gRPC client. Moreover, the trait also adds methods to tonic::Status that can be used by a tonic client to extract error details, and handle them with ease.

Getting Started

To build this crate you must have the Protocol Buffer Compiler, protoc, installed. Instructions can be found here.

[dependencies]
tonic = "0.8"
tonic-richer-error = "0.3"

Examples

The examples bellow cover a basic use case. More complete server and client implementations can be found at the examples directory.

Server Side: Generating tonic::Status with an ErrorDetails struct

use tonic::{Code, Status};
use tonic_richer_error::{ErrorDetails, WithErrorDetails};

// ...
// Inside a gRPC server endpoint that returns `Result<Response<T>, Status>`

// Create empty `ErrorDetails` struct
let mut err_details = ErrorDetails::new();

// Add error details conditionally
if some_condition {
    err_details.add_bad_request_violation(
        "field_a",
        "description of why the field_a is invalid"
    );
}

if other_condition {
    err_details.add_bad_request_violation(
        "field_b",
        "description of why the field_b is invalid",
    );
}

// Check if any error details were set and return error status if so
if err_details.has_bad_request_violations() {

    // Add additional error details if necessary
    err_details
        .add_help_link("description of link", "https://resource.example.local")
        .set_localized_message("en-US", "message for the user");

    let status = Status::with_error_details(
        Code::InvalidArgument,
        "bad request",
        err_details,
    );

    return Err(status);
}

// Handle valid request

// ...

Client Side: Extracting an ErrorDetails struct from tonic::Status

use tonic::{Response, Status};
use tonic_richer_error::WithErrorDetails;

// ...

// Where `req_result` was returned by a gRPC client endpoint method
fn handle_request_result<T>(req_result: Result<Response<T>, Status>) {
    match req_result {
        Ok(response) => {
            // Handle successful response
        },
        Err(status) => {
            let err_details = status.get_error_details();
            if let Some(bad_request) = err_details.bad_request {
                // Handle bad_request details
            }
            if let Some(help) = err_details.help {
                // Handle help details
            }
            if let Some(localized_message) = err_details.localized_message {
                // Handle localized_message details
            }
        }
    };
}

Send different standard error messages

Multiple examples are provided at the ErrorDetails doc. Instructions about how to use the fields of the standard error message types correctly are provided at error_details.proto.

Alternative tonic::Status associated functions and methods

In the WithErrorDetails doc, an alternative way of interacting with tonic::Status is presented, using vectors of error details structs wrapped with the ErrorDetail enum. This approach can provide more control over the vector of standard error messages that will be generated or that was received, if necessary. To see how to adopt this approach, please check the WithErrorDetails::with_error_details_vec and WithErrorDetails::get_error_details_vec docs, and also the examples directory.

Besides that, multiple examples with alternative error details extraction methods are provided in the WithErrorDetails doc, which can be specially useful if only one type of standard error message is being handled by the client. For example, using WithErrorDetails::get_details_bad_request is a more direct way of extracting a BadRequest error message from tonic::Status.

License

This project is licensed under the MIT license.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion by you, shall be licensed as MIT, without any additional terms or conditions.