bun/no-unhandled-emitter-errors

When an event emitter emits error and nobody listens for it, the error is thrown instead. A try around the call doesn't catch it, because it happens later. So spawn("gti") with a typo, or createReadStream() on a file that's gone, ends the whole process.

The rule looks at what these functions return:

Module	Functions
`node:child_process`	`spawn`, `fork`
`node:cluster`	`fork`
`node:fs`	`createReadStream`, `createWriteStream`, `watch`
`node:http`, `node:https`	`request`, `get`
`node:http2`, `node:tls`	`connect`
`node:net`	`connect`, `createConnection`

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"bun/no-unhandled-emitter-errors" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"bun/no-unhandled-emitter-errors" = ["error", {
  factories = [], # list of objects
}]

Examples#

example.js1 problem

import { spawn } from "node:child_process";

const child = spawn("git", ["status", "--short"]);
child.stdout.on("data", show);
child.on("exit", done);

pipe() doesn't pass errors on, so the source still needs a listener:

example.js1 problem

import { createReadStream } from "node:fs";

createReadStream(file).pipe(response);

example.jsNo problems

import { spawn } from "node:child_process";

const child = spawn("git", ["status", "--short"]);
child.stdout.on("data", show);
child.on("exit", done);
child.on("error", fail);

example.jsNo problems

import { createReadStream } from "node:fs";

createReadStream(file).on("error", fail).pipe(response);

An emitter that's returned, exported or passed to another function isn't reported, because the listener might be added there. pipeline() handles its streams' errors:

example.jsNo problems

import { createReadStream } from "node:fs";
import { pipeline } from "node:stream/promises";

await pipeline(createReadStream(file), response);

export function open(path) {
  return createReadStream(path);
}

export const log = createReadStream("app.log");

Options#

Option	Default	What it does
`factories`	`[]`	More functions that return an emitter, checked in addition to the table above. Each entry is `{ module, names }`, with the import specifier and the function names. Without `names`, the default export is the function.

bunfig.toml

[lint.rules]
"bun/no-unhandled-emitter-errors" = ["error", {
  factories = [{ module = "ws", names = ["createWebSocketStream"] }],
}]

example.jswith { "factories": [{ "module": "ws", "names": ["createWebSocketStream"] }] }1 problem

import { createWebSocketStream } from "ws";

const stream = createWebSocketStream(socket);
stream.on("data", show);