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feat: initial release

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Víctor Martínez 2026-01-19 23:25:18 +01:00 committed by JasterV
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version: 2
updates:
- package-ecosystem: "cargo"
directory: "/"
schedule:
interval: "daily"
time: "09:00"
- package-ecosystem: "github-actions"
directory: "/"
schedule:
interval: "weekly"

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name: Release-plz
on:
push:
branches:
- main
jobs:
# Release unpublished packages.
release-plz-release:
name: Release-plz release
runs-on: ubuntu-latest
permissions:
contents: write
steps:
- &checkout
name: Checkout repository
uses: actions/checkout@v6
with:
fetch-depth: 0
persist-credentials: false
- &install-rust
name: Install Rust toolchain
uses: dtolnay/rust-toolchain@stable
- name: Run release-plz
uses: release-plz/action@v0.5
with:
command: release
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_AUTH_KEY }}
# Create a PR with the new versions and changelog, preparing the next release.
release-plz-pr:
name: Release-plz PR
runs-on: ubuntu-latest
permissions:
contents: write
pull-requests: write
concurrency:
group: release-plz-${{ github.ref }}
cancel-in-progress: false
steps:
- *checkout
- *install-rust
- name: Run release-plz
uses: release-plz/action@v0.5
with:
command: release-pr
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_AUTH_KEY }}

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name: CI
on:
push:
branches:
- main
pull_request:
concurrency:
group: ci-${{ github.head_ref || github.ref }}
cancel-in-progress: true
env:
CARGO_TERM_COLOR: always
jobs:
ci:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v6
- run: rustup default 1.92.0
- run: rustup component add clippy rustfmt
- uses: Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1 # ratchet:Swatinem/rust-cache@v2
- uses: taiki-e/install-action@ae532dedd825648efd18d9c49c9a443d0398ca0a # ratchet:taiki-e/install-action@cargo-make
- name: Install protoc compiler
run: |
sudo apt update -y
sudo apt install -y protobuf-compiler
- run: cargo make ci
- run: cargo make test
alls-green:
if: always()
runs-on: ubuntu-latest
needs:
- ci
steps:
- run: ${{ !contains(needs.*.result, 'failure') }}

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/target

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grab/CHANGELOG.md

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[workspace]
members = ["grab", "echo-service"]
resolver = "2"

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[config]
# Sets the default task to run when executing `cargo make` without arguments
default_to_workspace = false
skip_core_tasks = true
# --- Main Flow Tasks ---
[tasks.default]
description = "Default task: Formats, Lints, and Builds"
dependencies = ["fmt", "clippy", "build"]
[tasks.ci]
description = "CI task: Runs checks without modifying files"
dependencies = ["fmt-check", "clippy", "test"]
# --- Atomic Tasks ---
[tasks.run]
description = "Runs the CLI tool with dynamic arguments"
command = "cargo"
# Added '-p grab' to explicitly target the CLI binary in the workspace
args = ["run", "-p", "grab", "${@}"]
[tasks.fmt]
description = "Formats all source files"
command = "cargo"
args = ["fmt", "--all"]
[tasks.fmt-check]
description = "Checks formatting without modifying files (fails if unformatted)"
command = "cargo"
args = ["fmt", "--all", "--", "--check"]
[tasks.clippy]
description = "Runs Clippy lints on the workspace"
command = "cargo"
# Added '--workspace' to lint both crates
args = [
"clippy",
"--workspace",
"--all-targets",
"--all-features",
"--",
"-D",
"warnings",
]
[tasks.test]
description = "Runs tests for the grab crate only"
command = "cargo"
# Added '-p grab' to strictly run integration/unit tests for the CLI
args = ["nextest", "run", "--no-fail-fast", "-p", "grab"]

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grab/README.md

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[package]
name = "echo-service"
edition = "2024"
publish = false
[dependencies]
bytes = "1"
prost = "0.14"
tonic = "0.14"
prost-types = "0.14"
tonic-prost = "0.14.2"
[build-dependencies]
tonic-prost-build = "0.14"

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use std::env::var;
use std::io::Result;
fn main() -> Result<()> {
// List of proto files containing a message definition
let proto_files = &[
// Services
"proto/echo.proto",
];
// Name of the folder containing the proto definitions
let proto_folder = "proto";
let out_dir = var("OUT_DIR").expect("Missing OUT_DIR environment variable");
let descriptors_path = format!("{}/descriptors.bin", out_dir);
tonic_prost_build::configure()
.file_descriptor_set_path(descriptors_path)
.protoc_arg("--experimental_allow_proto3_optional")
.build_client(false)
.compile_protos(proto_files, &[proto_folder])
.unwrap();
Ok(())
}

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syntax = "proto3";
package echo;
service EchoService {
rpc UnaryEcho (EchoRequest) returns (EchoResponse);
rpc ServerStreamingEcho (EchoRequest) returns (stream EchoResponse);
rpc ClientStreamingEcho (stream EchoRequest) returns (EchoResponse);
rpc BidirectionalEcho (stream EchoRequest) returns (stream EchoResponse);
}
message EchoRequest {
string message = 1;
}
message EchoResponse {
string message = 1;
}

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//! # Echo Service
//!
//! **INTERNAL USE ONLY**: This crate exists solely to provide a gRPC server implementation
//! and descriptor set for integration testing the `grab` CLI tool.
//! It is not intended for production use.
pub mod pb {
include!(concat!(env!("OUT_DIR"), "/echo.rs"));
}
pub use pb::echo_service_server::{EchoService, EchoServiceServer};
pub const FILE_DESCRIPTOR_SET: &[u8] = tonic::include_file_descriptor_set!("descriptors");

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# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## [Unreleased]
## `grab` - [0.1.0](https://github.com/JasterV/grab/compare/grab-v0.1.0...grab-v0.1.1) - 2026-01-20
### Added
- **Dynamic gRPC Client**: Implemented a CLI that performs gRPC calls without generating Rust code, bridging JSON payloads to Protobuf binary format at runtime.
- **Schema Loading**: Support for loading Protobuf schemas dynamically from binary `FileDescriptorSet` (`.bin` or `.pb`) files.
- **Full Streaming Support**: Automatic dispatch for all four gRPC access patterns based on the method descriptor:
- Unary (Single Request → Single Response)
- Server Streaming (Single Request → Stream)
- Client Streaming (Stream → Single Response)
- Bidirectional Streaming (Stream → Stream)
- **JSON Transcoding**: Custom `tonic::Codec` implementation (`JsonCodec`) to validate and transcode `serde_json::Value` to/from Protobuf bytes on the fly.
- **Metadata Support**: Ability to attach custom headers/metadata to requests via the `-H` / `--header` flag.
- **Input Validation**: Fast-fail validation that checks if the provided JSON structure is valid before making the network request.

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[package]
authors = ["Victor Martínez Montané <jaster.victor@gmail.com>"]
categories = ["network-programming", "command-line-utilities"]
description = "A dynamic gRPC CLI tool written in Rust (gRPC + Crab)"
edition = "2024"
homepage = "https://github.com/JasterV/grab"
keywords = ["cli", "command-line", "grpc", "grpcurl", "curl"]
license = "MIT OR Apache-2.0"
name = "grab"
publish = true
readme = "README.md"
repository = "https://github.com/JasterV/grab"
rust-version = "1.89"
version = "0.1.0"
[dependencies]
anyhow = "1.0.100"
clap = { version = "4.5.54", features = ["derive"] }
futures-util = "0.3.31"
http = "1.4.0"
http-body = "1.0.1"
prost = "0.14.3"
prost-reflect = { version = "0.16.3", features = ["serde"] }
serde_json = "1.0.149"
thiserror = "2.0.18"
tokio = { version = "1.49.0", features = ["rt-multi-thread", "macros"] }
tokio-stream = "0.1.18"
tonic = "0.14.2"
[dev-dependencies]
echo-service = { path = "../echo-service" }
tokio = { version = "1", features = ["rt-multi-thread", "macros", "test-util"] }

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# gRab 🦀
> ⚠️ **Status: Experimental**
>
> This project is currently in a **highly experimental phase**. It is a working prototype intended for testing and development purposes. APIs, command-line arguments, and internal logic are subject to breaking changes. Please use with caution.
**gRab** (gRPC + Crab) is a lightweight, dynamic gRPC CLI tool written in Rust.
It allows you to make gRPC calls to any server using simple JSON payloads, without needing to compile the specific Protobuf files into the client. By loading a `FileDescriptorSet` at runtime, gRab acts as a bridge between human-readable JSON and binary Protobuf wire format.
It is heavily inspired by tools like `grpcurl` but built to leverage the safety and performance of the Rust ecosystem (Tonic + Prost).
## 🚀 Features
* **Dynamic Encoding/Decoding**: Transcodes JSON to Protobuf (and vice versa) on the fly using `prost-reflect`.
* **Smart Dispatch**: Automatically detects if a call is Unary, Server Streaming, Client Streaming, or Bidirectional based on the descriptor.
* **Fast Fail Validation**: Validates your JSON *before* hitting the network.
* **Zero Compilation Dependencies**: Does not require generating Rust code for your protos. Just point to a descriptor file.
* **Metadata Support**: Easily attach custom headers (authorization, tracing) to your requests.
* **Tonic 0.14**: Built on the latest stable Rust gRPC stack.
## 📦 Installation
### From Source
Ensure you have Rust and Cargo installed.
```bash
git clone https://github.com/JasterV/grab
cd grab
cargo install --path .
```
## 🛠️ Prerequisites: Generating Descriptors
To use gRab, you currently need a binary **FileDescriptorSet** (`.bin` or `.pb`). This file contains the schema definitions for your services.
You can generate this using the standard `protoc` compiler:
```bash
# Generate descriptor.bin including all imports
protoc \
--include_imports \
--descriptor_set_out=descriptor.bin \
--proto_path=. \
my_service.proto
```
> **Note**: The `--include_imports` flag is crucial. It ensures that types defined in imported files (like `google/protobuf/timestamp.proto`) are available for reflection.
## 📖 Usage
**Syntax:**
```bash
grab [OPTIONS] <URL> <METHOD>
```
### Arguments
| Argument | Description | Required |
| --- | --- | --- |
| `<URL>` | Server address (e.g., `http://[::1]:50051`). | **Yes** |
| `<METHOD>` | Fully qualified method name (e.g., `my.package.Service/Method`). | **Yes** |
### Options
| Flag | Short | Description | Required |
| --- | --- | --- | --- |
| `--proto-set` | | Path to the binary FileDescriptorSet (`.bin`). | **Yes** |
| `--body` | | The request body in JSON format. | **Yes** |
| `--header` | `-H` | Custom header `key:value`. Can be used multiple times. | No |
### JSON Body Format
* **Unary / Server Streaming**: Provide a single JSON object `{ ... }`.
* **Client / Bidirectional Streaming**: Provide a JSON array of objects `[ { ... }, { ... } ]`.
### Examples
**1. Unary Call**
```bash
grab \
--proto-set ./descriptor.bin \
--body '{"name": "Ferris"}' \
http://localhost:50051 \
helloworld.Greeter/SayHello
```
**2. Bidirectional Streaming (Chat)**
```bash
grab \
--proto-set ./descriptor.bin \
--body '[{"text": "Hello"}, {"text": "How are you?"}]' \
-H "authorization: Bearer token123" \
http://localhost:50051 \
chat.ChatService/StreamMessages
```
## 🔮 Roadmap
* **Automatic Server Reflection**: We are working on removing the requirement for the `--proto-set` file. Future versions will support fetching the schema directly from servers that have the [gRPC Server Reflection Protocol](https://github.com/grpc/grpc/blob/master/doc/server-reflection.md) enabled.
* **Interactive Mode**: A REPL for streaming requests interactively.
* **Pretty Printing**: Enhanced colored output for JSON responses.
## ⚠️ Common Errors
**1. `Service 'x' not found**`
* **Cause:** The service name in the command does not match the package defined in your proto file.
* **Fix:** Check your `.proto` file. If it has `package my.app;` and `service API {}`, the full name is `my.app.API`.
**2. `Method 'y' not found in service 'x'**`
* **Cause:** Typo in the method name or the method doesn't exist.
* **Fix:** Ensure case sensitivity matches (e.g., `GetUser` vs `getUser`).
**3. `h2 protocol error**`
* **Cause:** This often occurs when the JSON payload fails to encode *after* the connection has already been established, or the server rejected the stream structure.
* **Fix:** Double-check your JSON payload against the Protobuf schema.
## 🤝 Contributing
Contributions are welcome! Please run the Makefile checks before submitting a PR:
```bash
cargo make # Formats, lints, and builds
```
## 📄 License
Licensed under either of:
* Apache License, Version 2.0 ([LICENSE-APACHE](http://www.apache.org/licenses/LICENSE-2.0))
* MIT license ([LICENSE-MIT](http://opensource.org/licenses/MIT))
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

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//! # gRPC Client Layer
//!
//! This module handles the low-level networking and `tonic` client construction.
//! It is decoupled from the descriptor logic and strictly focuses on sending
//! requests and receiving responses using the `JsonCodec`.
//!
//! # Error Handling
//!
//! - **`ClientError`**: Represents transport errors (connection refused, DNS resolution),
//! configuration errors (invalid URI), or usage errors (invalid headers).
//! - **`tonic::Status`**: Represents a successful HTTP interaction where the gRPC server
//! returned an error code (e.g., `NOT_FOUND`, `UNAUTHENTICATED`).
//!
//! The methods in `GrpcClient` separate these two types of errors by returning
//! `Result<Result<T, Status>, ClientError>`.
use crate::codec::JsonCodec;
use futures_util::Stream;
use prost_reflect::MethodDescriptor;
use std::str::FromStr;
use thiserror::Error;
use tonic::{
Request,
client::Grpc,
metadata::{
MetadataKey, MetadataValue,
errors::{InvalidMetadataKey, InvalidMetadataValue},
},
transport::Channel,
};
#[cfg(test)]
mod integration_test;
/// Represents failures that occur *before* or during the establishment of the network call,
/// or protocol violations that prevent a response.
#[derive(Error, Debug)]
pub enum ClientError {
#[error("Invalid uri '{addr}' provided: '{source}'")]
InvalidUri {
addr: String,
source: http::uri::InvalidUri,
},
#[error("Failed to connect: '{0}'")]
ConnectionFailed(tonic::transport::Error),
#[error("Internal error, the client was not ready: '{0}'")]
ClientNotReady(tonic::transport::Error),
#[error("Invalid metadata (header) key '{key}': '{source}'")]
InvalidMetadataKey {
key: String,
source: InvalidMetadataKey,
},
#[error("Invalid metadata (header) value for key '{key}': '{source}'")]
InvalidMetadataValue {
key: String,
source: InvalidMetadataValue,
},
}
/// A generic gRPC client that uses dynamic dispatch via `prost-reflect`.
pub struct GrpcClient {
channel: Channel,
}
impl GrpcClient {
/// Connects to the specified gRPC server address.
///
/// # Arguments
/// * `addr` - The URI of the server (e.g., `http://localhost:50051`).
pub async fn connect(addr: &str) -> Result<Self, ClientError> {
let uri =
tonic::transport::Uri::from_str(addr).map_err(|source| ClientError::InvalidUri {
addr: addr.to_string(),
source,
})?;
let channel = Channel::builder(uri)
.connect()
.await
.map_err(ClientError::ConnectionFailed)?;
Ok(Self { channel })
}
/// Performs a Unary gRPC call (Single Request -> Single Response).
///
/// # Returns
/// * `Ok(Ok(Value))` - Successful RPC execution.
/// * `Ok(Err(Status))` - RPC executed, but server returned an error.
/// * `Err(ClientError)` - Failed to send request or connect.
pub async fn unary(
&self,
method: MethodDescriptor,
payload: serde_json::Value,
headers: Vec<(String, String)>,
) -> Result<Result<serde_json::Value, tonic::Status>, ClientError> {
let mut client = Grpc::new(self.channel.clone());
client.ready().await.map_err(ClientError::ClientNotReady)?;
let codec = JsonCodec::new(method.input(), method.output());
let path = http_path(&method);
let request = build_request(payload, headers)?;
match client.unary(request, path, codec).await {
Ok(response) => Ok(Ok(response.into_inner())),
Err(status) => Ok(Err(status)),
}
}
/// Performs a Server Streaming gRPC call (Single Request -> Stream of Responses).
pub async fn server_streaming(
&self,
method: MethodDescriptor,
payload: serde_json::Value,
headers: Vec<(String, String)>,
) -> Result<
Result<impl Stream<Item = Result<serde_json::Value, tonic::Status>>, tonic::Status>,
ClientError,
> {
let mut client = Grpc::new(self.channel.clone());
client.ready().await.map_err(ClientError::ClientNotReady)?;
let codec = JsonCodec::new(method.input(), method.output());
let path = http_path(&method);
let request = build_request(payload, headers)?;
match client.server_streaming(request, path, codec).await {
Ok(response) => Ok(Ok(response.into_inner())),
Err(status) => Ok(Err(status)),
}
}
/// Performs a Client Streaming gRPC call (Stream of Requests -> Single Response).
pub async fn client_streaming(
&self,
method: MethodDescriptor,
payload_stream: impl Stream<Item = serde_json::Value> + Send + 'static,
headers: Vec<(String, String)>,
) -> Result<Result<serde_json::Value, tonic::Status>, ClientError> {
let mut client = Grpc::new(self.channel.clone());
client.ready().await.map_err(ClientError::ClientNotReady)?;
let codec = JsonCodec::new(method.input(), method.output());
let path = http_path(&method);
let request = build_request(payload_stream, headers)?;
match client.client_streaming(request, path, codec).await {
Ok(response) => Ok(Ok(response.into_inner())),
Err(status) => Ok(Err(status)),
}
}
/// Performs a Bidirectional Streaming gRPC call (Stream of Requests -> Stream of Responses).
pub async fn bidirectional_streaming(
&self,
method: MethodDescriptor,
payload_stream: impl Stream<Item = serde_json::Value> + Send + 'static,
headers: Vec<(String, String)>,
) -> Result<
Result<impl Stream<Item = Result<serde_json::Value, tonic::Status>>, tonic::Status>,
ClientError,
> {
let mut client = Grpc::new(self.channel.clone());
client.ready().await.map_err(ClientError::ClientNotReady)?;
let codec = JsonCodec::new(method.input(), method.output());
let path = http_path(&method);
let request = build_request(payload_stream, headers)?;
match client.streaming(request, path, codec).await {
Ok(response) => Ok(Ok(response.into_inner())),
Err(status) => Ok(Err(status)),
}
}
}
fn http_path(method: &MethodDescriptor) -> http::uri::PathAndQuery {
let path = format!("/{}/{}", method.parent_service().full_name(), method.name());
http::uri::PathAndQuery::from_str(&path).expect("valid gRPC path")
}
fn build_request<T>(payload: T, headers: Vec<(String, String)>) -> Result<Request<T>, ClientError> {
let mut request = Request::new(payload);
for (k, v) in headers {
let key = MetadataKey::from_str(&k).map_err(|source| ClientError::InvalidMetadataKey {
key: k.clone(),
source,
})?;
let val = MetadataValue::from_str(&v)
.map_err(|source| ClientError::InvalidMetadataValue { key: k, source })?;
request.metadata_mut().insert(key, val);
}
Ok(request)
}

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use crate::{client::GrpcClient, descriptor::DescriptorRegistry};
use echo_service::EchoServiceServer;
use echo_service::FILE_DESCRIPTOR_SET;
use echo_service_impl::EchoServiceImpl;
use tokio_stream::StreamExt;
use tonic::transport::Server;
mod echo_service_impl;
async fn spawn_server() -> String {
let listener = tokio::net::TcpListener::bind("0.0.0.0:0").await.unwrap();
let addr = listener.local_addr().unwrap();
tokio::spawn(async move {
Server::builder()
.add_service(EchoServiceServer::new(EchoServiceImpl))
.serve_with_incoming(tokio_stream::wrappers::TcpListenerStream::new(listener))
.await
.unwrap();
});
format!("http://{}", addr)
}
#[tokio::test]
async fn test_unary() {
let url = spawn_server().await;
let registry = DescriptorRegistry::from_bytes(FILE_DESCRIPTOR_SET).unwrap();
let method = registry
.fetch_method_descriptor("echo.EchoService/UnaryEcho")
.unwrap();
let client = GrpcClient::connect(&url).await.unwrap();
let payload = serde_json::json!({ "message": "hello" });
let res = client
.unary(method, payload, vec![])
.await
.unwrap()
.unwrap();
assert_eq!(res["message"], "hello");
}
#[tokio::test]
async fn test_server_streaming() {
let url = spawn_server().await;
let registry = DescriptorRegistry::from_bytes(FILE_DESCRIPTOR_SET).unwrap();
let method = registry
.fetch_method_descriptor("echo.EchoService/ServerStreamingEcho")
.unwrap();
let client = GrpcClient::connect(&url).await.unwrap();
let payload = serde_json::json!({ "message": "stream" });
let stream = client
.server_streaming(method, payload, vec![])
.await
.unwrap()
.unwrap();
let results: Vec<_> = stream.map(|r| r.unwrap()).collect().await;
assert_eq!(results.len(), 3);
assert_eq!(results[0]["message"], "stream - seq 0");
assert_eq!(results[1]["message"], "stream - seq 1");
assert_eq!(results[2]["message"], "stream - seq 2");
}
#[tokio::test]
async fn test_client_streaming() {
let url = spawn_server().await;
let registry = DescriptorRegistry::from_bytes(FILE_DESCRIPTOR_SET).unwrap();
let method = registry
.fetch_method_descriptor("echo.EchoService/ClientStreamingEcho")
.unwrap();
let client = GrpcClient::connect(&url).await.unwrap();
let payload = serde_json::json!([
{ "message": "A" },
{ "message": "B" },
{ "message": "C" }
]);
let stream_source = tokio_stream::iter(payload.as_array().unwrap().clone());
let res = client
.client_streaming(method, stream_source, vec![])
.await
.unwrap()
.unwrap();
assert_eq!(res["message"], "ABC");
}
#[tokio::test]
async fn test_bidirectional_streaming() {
let url = spawn_server().await;
let registry = DescriptorRegistry::from_bytes(FILE_DESCRIPTOR_SET).unwrap();
let method = registry
.fetch_method_descriptor("echo.EchoService/BidirectionalEcho")
.unwrap();
let client = GrpcClient::connect(&url).await.unwrap();
let payload = serde_json::json!([
{ "message": "Ping" },
{ "message": "Pong" }
]);
let stream_source = tokio_stream::iter(payload.as_array().unwrap().clone());
let response_stream = client
.bidirectional_streaming(method, stream_source, vec![])
.await
.unwrap()
.unwrap();
let results: Vec<_> = response_stream.map(|r| r.unwrap()).collect().await;
assert_eq!(results.len(), 2);
assert_eq!(results[0]["message"], "echo: Ping");
assert_eq!(results[1]["message"], "echo: Pong");
}

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grab/src/client/integration_test/echo_service_impl.rs Normal file
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use echo_service::EchoService;
use echo_service::pb::{EchoRequest, EchoResponse};
use futures_util::Stream;
use std::pin::Pin;
use tokio::sync::mpsc;
use tokio_stream::{StreamExt, wrappers::ReceiverStream};
use tonic::{Request, Response, Status, Streaming};
pub struct EchoServiceImpl;
#[tonic::async_trait]
impl EchoService for EchoServiceImpl {
type BidirectionalEchoStream = Pin<Box<dyn Stream<Item = Result<EchoResponse, Status>> + Send>>;
type ServerStreamingEchoStream = ReceiverStream<Result<EchoResponse, Status>>;
async fn unary_echo(
&self,
request: Request<EchoRequest>,
) -> Result<Response<EchoResponse>, Status> {
Ok(Response::new(EchoResponse {
message: request.into_inner().message,
}))
}
async fn server_streaming_echo(
&self,
request: Request<EchoRequest>,
) -> Result<Response<Self::ServerStreamingEchoStream>, Status> {
let msg = request.into_inner().message;
let (tx, rx) = mpsc::channel(4);
tokio::spawn(async move {
for i in 0..3 {
let response = EchoResponse {
message: format!("{} - seq {}", msg, i),
};
tx.send(Ok(response)).await.ok();
}
});
Ok(Response::new(ReceiverStream::new(rx)))
}
async fn client_streaming_echo(
&self,
request: Request<Streaming<EchoRequest>>,
) -> Result<Response<EchoResponse>, Status> {
let mut stream = request.into_inner();
let mut full_msg = String::new();
while let Some(req) = stream.next().await {
let req = req?;
full_msg.push_str(&req.message);
}
Ok(Response::new(EchoResponse { message: full_msg }))
}
async fn bidirectional_echo(
&self,
request: Request<Streaming<EchoRequest>>,
) -> Result<Response<Self::BidirectionalEchoStream>, Status> {
let mut in_stream = request.into_inner();
let (tx, rx) = mpsc::channel(128);
tokio::spawn(async move {
while let Some(result) = in_stream.next().await {
match result {
Ok(req) => {
let resp = EchoResponse {
message: format!("echo: {}", req.message),
};
if tx.send(Ok(resp)).await.is_err() {
break;
}
}
Err(e) => {
let _ = tx.send(Err(e)).await;
break;
}
}
}
});
Ok(Response::new(Box::pin(ReceiverStream::new(rx))))
}
}

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//! # JSON <-> Protobuf Codec
//!
//! This module implements a custom `tonic::codec::Codec` that allows `tonic` to work
//! directly with `serde_json::Value`.
//!
//! It acts as a bridge:
//! - **Encoding (Request):** Takes a JSON value -> Validates against Schema -> Serializes to Protobuf bytes.
//! - **Decoding (Response):** Takes Protobuf bytes -> Deserializes using Schema -> Converts to JSON value.
use prost::Message;
use prost_reflect::{DynamicMessage, MessageDescriptor};
use tonic::{
Status,
codec::{Codec, DecodeBuf, Decoder, EncodeBuf, Encoder},
};
/// A custom Codec that bridges `serde_json::Value` and Protobuf binary format.
///
/// It holds the descriptors (schemas) for both the request and the response messages,
/// allowing it to perform dynamic serialization.
pub struct JsonCodec {
/// Schema for the input message.
req_desc: MessageDescriptor,
/// Schema for the output message.
res_desc: MessageDescriptor,
}
impl JsonCodec {
/// Creates a new `JsonCodec`.
///
/// # Arguments
/// * `req_desc` - Descriptor for the request message type.
/// * `res_desc` - Descriptor for the response message type.
pub fn new(req_desc: MessageDescriptor, res_desc: MessageDescriptor) -> Self {
Self { req_desc, res_desc }
}
}
impl Codec for JsonCodec {
type Encode = serde_json::Value;
type Decode = serde_json::Value;
type Encoder = JsonEncoder;
type Decoder = JsonDecoder;
fn encoder(&mut self) -> Self::Encoder {
JsonEncoder(self.req_desc.clone())
}
fn decoder(&mut self) -> Self::Decoder {
JsonDecoder(self.res_desc.clone())
}
}
/// Responsible for encoding a JSON value into Protobuf bytes.
pub struct JsonEncoder(MessageDescriptor);
impl Encoder for JsonEncoder {
type Item = serde_json::Value;
type Error = Status;
fn encode(&mut self, item: Self::Item, dst: &mut EncodeBuf<'_>) -> Result<(), Self::Error> {
// DynamicMessage::deserialize accepts any Serde Deserializer.
// serde_json::Value implements IntoDeserializer, so we can pass it directly.
let msg = DynamicMessage::deserialize(self.0.clone(), item).map_err(|e| {
Status::invalid_argument(format!(
"JSON structure does not match Protobuf schema: {}",
e
))
})?;
msg.encode_raw(dst);
Ok(())
}
}
/// Responsible for decoding Protobuf bytes into a JSON value.
pub struct JsonDecoder(MessageDescriptor);
impl Decoder for JsonDecoder {
type Item = serde_json::Value;
type Error = Status;
fn decode(&mut self, src: &mut DecodeBuf<'_>) -> Result<Option<Self::Item>, Self::Error> {
// 1. Decode Bytes -> DynamicMessage
let mut msg = DynamicMessage::new(self.0.clone());
msg.merge(src)
.map_err(|e| Status::internal(format!("Failed to decode Protobuf bytes: {}", e)))?;
// 2. DynamicMessage -> serde_json::Value
// We convert the DynamicMessage into a Value structure.
// This is efficient and keeps the Client working with structured data.
let value = serde_json::to_value(&msg)
.map_err(|e| Status::internal(format!("Failed to map response to JSON: {}", e)))?;
Ok(Some(value))
}
}

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//! # Descriptor Registry
//!
//! This module handles the loading and querying of Protobuf `FileDescriptorSet`s.
//! It acts as a database of schema definitions, allowing the application to
//! resolve service and method names into `MethodDescriptor` objects required
//! for reflection.
use prost_reflect::{DescriptorPool, MethodDescriptor};
use std::path::Path;
use thiserror::Error;
#[derive(Error, Debug)]
pub enum DescriptorError {
#[error("Failed to read descriptor file: {0}")]
Io(#[from] std::io::Error),
#[error("Failed to decode descriptor set: {0}")]
Decode(#[from] prost_reflect::DescriptorError),
#[error("Service '{0}' not found")]
ServiceNotFound(String),
#[error("Method '{0}' not found")]
MethodNotFound(String),
#[error("Invalid method path. Expected format 'package.Service/Method', got '{0}'")]
InvalidFormat(String),
}
/// A registry that holds loaded Protobuf definitions and allows looking up
/// services and methods by name.
pub struct DescriptorRegistry {
pool: DescriptorPool,
}
impl DescriptorRegistry {
/// Decodes a FileDescriptorSet directly from a byte slice.
/// Useful for tests or embedded descriptors.
#[cfg(test)]
pub fn from_bytes(bytes: &[u8]) -> Result<Self, DescriptorError> {
let pool = DescriptorPool::decode(bytes)?;
Ok(Self { pool })
}
/// Loads a FileDescriptorSet from a file on disk and builds the registry.
pub fn from_file(path: impl AsRef<Path>) -> Result<Self, DescriptorError> {
let bytes = std::fs::read(path)?;
let pool = DescriptorPool::decode(bytes.as_slice())?;
Ok(Self { pool })
}
/// Resolves a full method path (e.g., "my.package.MyService/MyMethod")
/// into a MethodDescriptor.
pub fn fetch_method_descriptor(
&self,
method_path: &str,
) -> Result<MethodDescriptor, DescriptorError> {
let (service_name, method_name) = method_path
.split_once('/')
.ok_or_else(|| DescriptorError::InvalidFormat(method_path.to_string()))?;
let service = self
.pool
.get_service_by_name(service_name)
.ok_or_else(|| DescriptorError::ServiceNotFound(service_name.to_string()))?;
service
.methods()
.find(|m| m.name() == method_name)
.ok_or_else(|| DescriptorError::MethodNotFound(method_name.to_string()))
}
}

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#![doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/README.md"))]
/// # gRab CLI Entry Point
///
/// The main module orchestrates the CLI workflow:
/// 1. Parses command-line arguments.
/// 2. Loads the Protobuf descriptor registry.
/// 3. Connects to the gRPC server.
/// 4. Dispatches the request to the appropriate method type (Unary, Streaming, etc.).
use clap::Parser;
use client::GrpcClient;
use descriptor::DescriptorRegistry;
use futures_util::{Stream, StreamExt};
use prost_reflect::MethodDescriptor;
use std::path::PathBuf;
use std::process;
mod client;
mod codec;
mod descriptor;
#[derive(Parser)]
#[command(name = "grab", version, about = "Dynamic gRPC CLI")]
struct Cli {
#[arg(long, help = "Path to the descriptor set (.bin)")]
proto_set: PathBuf,
#[arg(long, help = "JSON body (Object for Unary, Array for Streaming)")]
body: String,
#[arg(short = 'H', long = "header", value_parser = parse_header)]
headers: Vec<(String, String)>,
#[arg(help = "Server URL (http://host:port)")]
url: String,
#[arg(help = "Method (package.Service/Method)")]
method: String,
}
fn parse_header(s: &str) -> Result<(String, String), String> {
s.split_once(':')
.map(|(k, v)| (k.trim().to_string(), v.trim().to_string()))
.ok_or_else(|| "Format must be 'key:value'".to_string())
}
#[tokio::main]
async fn main() {
if let Err(e) = run().await {
eprintln!("Error: {}", e);
process::exit(1);
}
}
async fn run() -> anyhow::Result<()> {
let args = Cli::parse();
let registry = DescriptorRegistry::from_file(&args.proto_set)?;
let method = registry.fetch_method_descriptor(&args.method)?;
let body_json: serde_json::Value =
serde_json::from_str(&args.body).map_err(|e| anyhow::anyhow!("Invalid JSON: {}", e))?;
let client = GrpcClient::connect(&args.url).await?;
println!("Calling {}...", args.method);
match (method.is_client_streaming(), method.is_server_streaming()) {
(false, false) => handle_unary(client, method, body_json, args.headers).await,
(false, true) => handle_server_stream(client, method, body_json, args.headers).await,
(true, false) => handle_client_stream(client, method, body_json, args.headers).await,
(true, true) => handle_bidirectional_stream(client, method, body_json, args.headers).await,
}
}
// --- Handlers ---
async fn handle_unary(
client: GrpcClient,
method: MethodDescriptor,
body: serde_json::Value,
headers: Vec<(String, String)>,
) -> anyhow::Result<()> {
match client.unary(method, body, headers).await? {
Ok(val) => print_json(&val),
Err(status) => print_status(status),
}
Ok(())
}
async fn handle_server_stream(
client: GrpcClient,
method: MethodDescriptor,
body: serde_json::Value,
headers: Vec<(String, String)>,
) -> anyhow::Result<()> {
match client.server_streaming(method, body, headers).await? {
Ok(stream) => print_stream(stream).await,
Err(status) => print_status(status),
}
Ok(())
}
async fn handle_client_stream(
client: GrpcClient,
method: MethodDescriptor,
body: serde_json::Value,
headers: Vec<(String, String)>,
) -> anyhow::Result<()> {
let input_stream = json_array_to_stream(body)?;
match client
.client_streaming(method, input_stream, headers)
.await?
{
Ok(val) => print_json(&val),
Err(status) => print_status(status),
}
Ok(())
}
async fn handle_bidirectional_stream(
client: GrpcClient,
method: MethodDescriptor,
body: serde_json::Value,
headers: Vec<(String, String)>,
) -> anyhow::Result<()> {
let input_stream = json_array_to_stream(body)?;
match client
.bidirectional_streaming(method, input_stream, headers)
.await?
{
Ok(stream) => print_stream(stream).await,
Err(status) => print_status(status),
}
Ok(())
}
// --- Helpers ---
fn json_array_to_stream(
json: serde_json::Value,
) -> anyhow::Result<impl Stream<Item = serde_json::Value> + Send + 'static> {
match json {
serde_json::Value::Array(items) => Ok(tokio_stream::iter(items)),
_ => Err(anyhow::anyhow!(
"Client streaming requires a JSON Array body"
)),
}
}
fn print_json(val: &serde_json::Value) {
println!(
"{}",
serde_json::to_string_pretty(val).unwrap_or_else(|_| val.to_string())
);
}
fn print_status(status: tonic::Status) {
eprintln!(
"gRPC Failed: code={:?} message={:?}",
status.code(),
status.message()
);
}
async fn print_stream(
mut stream: impl Stream<Item = Result<serde_json::Value, tonic::Status>> + Unpin,
) {
while let Some(result) = stream.next().await {
match result {
Ok(val) => print_json(&val),
Err(status) => print_status(status),
}
}
}

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release-plz.toml Normal file
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[workspace]
# set the path of all the crates to the changelog to the root of the repository
changelog_path = "./CHANGELOG.md"
pr_draft = true
pr_labels = ["release"]
pr_branch_prefix = "release-"
[changelog]
body = """
## `{{ package }}` - [{{ version }}]{%- if release_link -%}({{ release_link }}){% endif %} - {{ timestamp | date(format="%Y-%m-%d") }}
{% for group, commits in commits | group_by(attribute="group") %}
### {{ group | upper_first }}
{% for commit in commits %}
{%- if commit.scope -%}
- *({{commit.scope}})* {% if commit.breaking %}[**breaking**] {% endif %}{{ commit.message }}{%- if commit.links %} ({% for link in commit.links %}[{{link.text}}]({{link.href}}) {% endfor -%}){% endif %}
{% else -%}
- {% if commit.breaking %}[**breaking**] {% endif %}{{ commit.message }}
{% endif -%}
{% endfor -%}
{% endfor -%}
"""

3
rust-toolchain.toml Normal file
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[toolchain]
channel = "1.92"
components = ["rustfmt", "clippy", "rust-src", "rust-analyzer"]

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yamlfmt.yml Normal file
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formatter:
type: basic
retain_line_breaks_single: true