Esbuild causing unhandledRejection

[JoshuaWise]

I have a program that uses esbuild internally. My program is designed such that it can be cancelled at any time via ctrl+c (SIGINT). When a SIGINT is received, it doesn't just exit the process abruptly, rather, it initiates a graceful shutdown procedure. However, sometimes when I do this, I get an unhandledRejection event from esbuild. It doesn't happen all the time; it's inconsistent, probably due to the timing of things.

Anyways, esbuild should never cause unhandledRejection events. I'm doing await esbuild.build() and catching any thrown errors within a try-catch block, so it should (ideally) be impossible for any errors within esbuild to escape as unhandledRejection events.

Here is the complete stderr output:

process.on('unhandledRejection', (err) => { throw err; });
                                            ^

Error: The service was stopped
    at /[redacted]/node_modules/esbuild/lib/main.js:1076:25
    at responseCallbacks.<computed> (/[redacted]/node_modules/esbuild/lib/main.js:700:9)
    at Socket.afterClose (/[redacted]/node_modules/esbuild/lib/main.js:690:28)
    at Socket.emit (node:events:525:35)
    at endReadableNT (node:internal/streams/readable:1359:12)
    at process.processTicksAndRejections (node:internal/process/task_queues:82:21)

Node.js v18.16.1

The version of esbuild is 0.18.10.

[evanw]

I was unable to reproduce this. Here's what I tried:

const esbuild = require('esbuild')

async function run() {
  try {
    await esbuild.build({
      entryPoints: ['entry'],
      plugins: [{
        name: 'temp',
        setup(build) {
          build.onResolve({ filter: /./ }, () => new Promise(() => { }))
        },
      }],
    })
  }

  // Comment this out to cause an unhandled rejection
  catch (err) { console.log('Caught:', err) }

  finally { }
}

process.on('unhandledRejection', err => {
  console.log('UNHANDLED REJECTION')
  throw err
})

console.log('Waiting for Ctrl+C...')
process.on('SIGINT', () => {
  console.log('Waiting for timeout...')
  setTimeout(() => console.log('Success'), 2000)
})

run()

It seems like esbuild is successfully funnelling the error to the build API call here.

Please provide a way to reproduce the issue. I'm marking this as unactionable until a way to reproduce this issue is provided.

Anyways, esbuild should never cause unhandledRejection events. I'm doing await esbuild.build() and catching any thrown errors within a try-catch block, so it should (ideally) be impossible for any errors within esbuild to escape as unhandledRejection events.

Agreed, and I'd like to fix this. It should be straightforward to fix this if I can reproduce it.

[JoshuaWise]

Below is a script that allows me to reproduce the unhandledRejection 100% of the time. Here are the steps:

1. Run the script below
2. Press ctrl+c to trigger a SIGINT before the build finishes
3. Wait for the build to finish

Here is the script:

const esbuild = require('esbuild');

async function main() {
    console.log('building...');

    await esbuild.build({
        entryPoints: ['entry.js'],
        write: false,
        bundle: true,
        plugins: [{
            name: 'loader',
            setup: (build) => {
                build.onResolve({ filter: /()/ }, async (args) => {
                    return { path: args.path, namespace: 'fake' };
                });
                build.onLoad({ filter: /()/, namespace: 'fake' }, async (args) => {
                    await sleep(2000);

                    if (args.path === 'entry.js') {
                        return {
                            loader: 'js',
                            contents: 'console.log(require("string.js"));',
                        };
                    }
                    if (args.path === 'string.js') {
                        return {
                            loader: 'js',
                            contents: 'module.exports = "hello world";',
                        };
                    }
                });
            },
        }],
    });

    console.log('done!');
}

async function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

process.on('SIGHUP', () => console.log('SIGHUP detected'));
process.on('SIGINT', () => console.log('SIGINT detected'));
process.on('SIGTERM', () => console.log('SIGTERM detected'));

process.on('unhandledRejection', (err) => {
    console.log('Unhandled rejection:', err);
});

main().catch((err) => {
    console.log('Error caught:', err);
});

The output I get is:

building...
^CSIGINT detected
Error caught: Error: The service was stopped
    at /[redacted]/node_modules/esbuild/lib/main.js:1076:25
    at responseCallbacks.<computed> (/[redacted]/node_modules/esbuild/lib/main.js:700:9)
    at Socket.afterClose (/[redacted]/node_modules/esbuild/lib/main.js:690:28)
    at Socket.emit (node:events:525:35)
    at endReadableNT (node:internal/streams/readable:1359:12)
    at process.processTicksAndRejections (node:internal/process/task_queues:82:21)
Unhandled rejection: Error: The service is no longer running
    at sendResponse (/[redacted]/node_modules/esbuild/lib/main.js:712:13)
    at handleRequest (/[redacted]/node_modules/esbuild/lib/main.js:733:7)

[JoshuaWise]

Thanks for fixing this! 👍