connect-to-devtools-pipe.js

const chromeFinder = require("chrome-launcher/dist/chrome-finder");
const { getPlatform } = require("chrome-launcher/dist/utils");
const execa = require("execa");
const { Transform } = require("stream");
const { inspect } = require("util");

let seq = 0;

function eachMessage() {
  /** @type {Buffer[]} */
  let chunks = [];
  /** @type {number} */
  let bytes = 0;

  /**
   * @param {Buffer} chunk
   * @param {number} start
   * @param {number=} end
   */
  function append(chunk, start, end) {
    const len = end - start;
    if (len > 0) {
      chunks.push(chunk.slice(start, end));
      bytes += len;
    }
  }

  function flush() {
    let value;
    if (chunks.length === 1) {
      value = chunks[0].toString();
    } else if (chunks.length > 1) {
      value = Buffer.concat(chunks, bytes).toString();
    }
    chunks.length = 0;
    bytes = 0;
    return value;
  }

  return new Transform({
    readableObjectMode: true,
    transform(chunk, _encoding, done) {
      let start = 0;
      let end = chunk.indexOf(0);

      while (end !== -1) {
        append(chunk, start, end);
        const message = flush();
        if (message !== undefined) {
          this.push(message);
        }
        start = end + 1;
        end = chunk.indexOf(0, start);
      }

      append(chunk, start);

      done();
    },
    flush(done) {
      const message = flush();
      if (message !== undefined) {
        this.push(message);
      }
      done();
    },
  });
}

function findChrome() {
  const platform = getPlatform();
  let chromePath;
  if (platform in chromeFinder) {
    const paths = chromeFinder[platform]();
    if (paths.length > 0) {
      chromePath = paths[0];
    }
  }
  if (chromePath === undefined) {
    throw new Error("unable to find chrome installation");
  }

  return chromePath;
}

const exec = findChrome();

const child = execa(
  exec,
  [
    "--remote-debugging-pipe",
    "--no-sandbox",
    "--no-experiments",
    "--metrics-recording-only",
    "--disable-background-networking",
    "--disable-sync",
    "--disable-extensions",
  ],
  {
    buffer: false,
    stdio: ["inherit", "inherit", "inherit", "pipe", "pipe"],
  },
);

child.on("error", err => {
  console.log("PROCESS ERROR", inspect(err));
});

child.on("close", () => {
  console.log("PROCESS CLOSE");
});

const output = child.stdio[4].pipe(eachMessage());
const input = child.stdio[3];

function send(method, params, sessionId) {
  const id = ++seq;
  const message = {
    id,
    method,
    params,
    sessionId,
  };
  console.log("SND", inspect(message));
  input.write(JSON.stringify(message));
  input.write("\0");
  return id;
}

let createId;

output.on("data", data => {
  // console.log("DATA", data);
  const message = JSON.parse(data);

  if ("id" in message) {
    console.log("RSP", inspect(message));
    if (message.id === createId) {
      const targetId = message.result.targetId;
      send("Target.attachToTarget", { targetId, flatten: true });
    }
  } else {
    console.log("EVT", inspect(message));
  }
});

send("Target.setDiscoverTargets", { discover: true });
createId = send("Target.createTarget", { url: "http://google.com" });

process.on("SIGINT", () => {
  send("Browser.close");
});

output.on("close", () => {
  console.log("PROCESS OUTPUT CLOSE");
});

input.on("close", () => {
  console.log("PROCESS INPUT CLOSE");
});