Crate cadencr_tab_backend 

Write the native backend of a Cadencr custom tab.

A custom tab may ship a native executable that Cadencr starts per conversation and talks to over stdin/stdout, one JSON object per line. The protocol is the contract — see docs/TAB_BACKEND_PROTOCOL.md — and this crate is one way to implement it:

use std::process::ExitCode;

use cadencr_tab_backend::{serve, Context, Error};
use serde_json::{json, Value};

fn handle(cx: &Context) -> Result<Value, Error> {
    match cx.method() {
        "greet" => {
            let name: String = cx.params()?;
            Ok(json!(format!("hello, {name}")))
        }
        other => Err(Error::unknown_method(other)),
    }
}

fn main() -> ExitCode {
    serve(handle)
}

serve reads and checks the hello, answers ready, then runs each request on a small worker pool (a slow request does not hold up the others; responses may be written out of order), turns a handler panic into an codes::INTERNAL_ERROR response, logs and skips malformed lines, and returns once stdin closes. On Unix it also reserves stdin and stdout for the protocol: anything else printed to stdout goes to stderr, the log, and child processes see /dev/null as stdin.

Features: api adds a blocking client for the Cadencr API (Context::api); conformance adds conformance::run, which checks any backend binary against the protocol. testing drives a handler in-process.

Re-exports

pub use protocol::PROTOCOL_VERSION;

Modules

api

A blocking client for the Cadencr API (feature api).

codes

Error codes this crate sends on its own. The protocol reserves them: a backend should use them only with the meaning given here.

conformance

Check a backend binary against the stdio protocol (feature conformance).

protocol

Reference types of the stdio protocol, version PROTOCOL_VERSION.

testing

Drive a handler in-process, without spawning a process.

Structs

Config

How serve_with runs requests.

Context

One request: its method, its params and the backend’s hello.

Error

A failed request: a stable SCREAMING_SNAKE_CASE code and a message for a person.

Enums

ServeError

Why a run ended before stdin closed.

Constants

SDK

ready.sdk of backends built with this crate.

Traits

Handler

Handles every request of one backend. Called concurrently from several worker threads, hence Send + Sync.

Functions

serve

Run handler as this process’s backend with the default Config. Returns once stdin closes; use it as main’s result.

serve_with

serve with an explicit Config.