Crate dap

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dap-rs, a Rust implementation of the Debug Adapter Protocol


This crate is a Rust implementation of the Debug Adapter Protocol (or DAP for short).

The best way to think of DAP is to compare it to LSP (Language Server Protocol) but for debuggers. The core idea is the same: a protocol that serves as lingua franca for editors and debuggers to talk to each other. This means that an editor that implements DAP can use a debugger that also implements DAP.

In practice, the adapter might be separate from the actual debugger. For example, one could implement an adapter that writes commands to the stdin of a gdb subprocess, then parses the output it receives (this is why it’s called an “adapter” - it adapts the debugger to editors that know DAP).

Minimal example

To get started, create a binary project and add dap to your Cargo.toml:

name = "dummy-server"
version = "*"
edition = "2021"

dap = "*"

Our dummy server is going to read its input from a text file and write the output to stdout.

use std::fs::File;
use std::io::{BufReader, BufWriter};

use thiserror::Error;

use dap::prelude::*;

#[derive(Error, Debug)]
enum MyAdapterError {
  #[error("Unhandled command")]

  #[error("Missing command")]

type DynResult<T> = std::result::Result<T, Box<dyn std::error::Error>>;

fn main() -> DynResult<()> {
  let output = BufWriter::new(std::io::stdout());
  let f = File::open("testinput.txt")?;
  let input = BufReader::new(f);
  let mut server = Server::new(input, output);

  let req = match server.poll_request()? {
    Some(req) => req,
    None => return Err(Box::new(MyAdapterError::MissingCommandError)),
  if let Command::Initialize(_) = req.command {
    let rsp = req.success(
      ResponseBody::Initialize(Some(types::Capabilities {

    // When you call respond, send_event etc. the message will be wrapped
    // in a base message with a appropriate seq number, so you don't have to keep track of that yourself

  } else {
    return Err(Box::new(MyAdapterError::UnhandledCommandError));

  // You can send events from other threads while the server is blocked
  // polling for requests by grabbing a `ServerOutput` mutex:
  let server_output = server.output.clone();
  std::thread::spawn(move || {

      let mut server_output = server_output.lock().unwrap();
          .send_event(Event::Capabilities(events::CapabilitiesEventBody {

  // The thread will concurrently send an event while we are polling
  // for the next request
  let _ = server.poll_request()?;