@typescript-eslint/no-confusing-void-expression

A function that returns void has no result to use. Code like const saved = save(user) or return log(error) suggests there is one, and the reader goes looking for a value that doesn't exist. A void call belongs on its own line.

A void call is still fine on the right of &&, || and ??, and in the branches of ? :, if the whole expression is a statement.

--fix adds braces to an arrow function, and takes the call out of a return. A void value that's assigned or passed on is reported but not fixed.

Configure

Off by default. This rule needs types, so turning it on makes bun lint type check your code first.

bunfig.toml

[lint.rules]
"@typescript-eslint/no-confusing-void-expression" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"@typescript-eslint/no-confusing-void-expression" = ["error", {
  ignoreArrowShorthand = false,
  ignoreVoidOperator = false,
  ignoreVoidReturningFunctions = false,
}]

Examples

Reported:

declare function log(message: string): void;

const result = log("saved");

const onSave = () => log("saved");

function onError(error: Error) {
  return log(error.message);
}

Not reported:

declare function log(message: string): void;
declare const verbose: boolean;

log("saved");
verbose && log("details");

const onSave = () => {
  log("saved");
};

function onError(error: Error) {
  log(error.message);
}

Options

Option	Default	What it does
`ignoreArrowShorthand`	`false`	Allow `() => log()`, an arrow function without braces.
`ignoreVoidOperator`	`false`	Allow a `void` expression anywhere if it's marked with the `void` operator. `--fix` then adds `void` in arrow functions and returns.
`ignoreVoidReturningFunctions`	`false`	Allow returning a `void` expression from a function that returns `void` itself.

declare function log(message: string): void;

["a", "b"].forEach(name => log(name));

With ignoreVoidOperator:

declare function log(message: string): void;

const onSave = () => void log("saved");

declare function log(message: string): void;

const onSave = () => log("saved");

With ignoreVoidReturningFunctions, the return type can be written on the function or come from where the function is used:

declare function log(message: string): void;

function onError(error: Error): void {
  return log(error.message);
}

["a", "b"].forEach(name => log(name));

declare function log(message: string): void;

function onError(error: Error) {
  return log(error.message);
}