It should be possible to handle SIGINT that is raised inside a looped prompt

[finleyjb]

Version: Deno 2.0.0

Given the following code:

// Example 1
Deno.addSignalListener("SIGINT", () => {
  console.log("interrupted!"); // Never prints
  Deno.exit();
});

while (true) {
  const val = prompt('Prompt: '); // Hit Ctrl-c while in this prompt
  console.log(val); // logs null
}

As it stands right now, this program will log a null and the SIGINT handler will never run. However, if I remove the loop and run this the SIGINT handler runs (adapted from the deno docs):

// Example 2
let sigint = false;
Deno.addSignalListener("SIGINT", () => {
  console.log("interrupted!");
  sigint = true;
});

const val = prompt("Prompt: ");
console.log(val); // prints null

// Add a timeout to prevent process exiting immediately.
setTimeout(() => {}, 5000); // prints "interrupted!"

The only workaround I've found is that you can yield control using a setTimeout in a promise:

// Example 3
Deno.addSignalListener("SIGINT", () => {
  console.log("interrupted!");
  Deno.exit(1);
});

while (true) {
  const val = prompt("Prompt: ");
  const printHandlerPromise = new Promise((resolve, reject) => {
    console.log(val);
    setTimeout(() => {
      resolve(null);
    }, 0);
  });
  await printHandlerPromise;
}

It seems like Example 1 should do something other than silently swallow the SIGINT function call. Perhaps the handler should run after the user inputs text at the next prompt?

[sigmaSd]

You can use node readline

import * as readline from "node:readline/promises";
import process from "node:process";

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});
rl.addListener("SIGINT", () => {
  console.log("interrupted!"); // Never prints
  Deno.exit();
});

while (true) {
  const val = await rl.question("Prompt: "); // Hit Ctrl-c while in this prompt
  console.log(val); // logs null
}

prompt api is problematic in deno, its synchronous and it blocks all async tasks in deno, i imagine its not the case in browsers implementation