typescript/no-misused-promises Pedantic ​
What it does ​
This rule forbids providing Promises to logical locations such as if statements in places where the TypeScript compiler allows them but they are not handled properly. These situations can often arise due to a missing await keyword or just a misunderstanding of the way async functions are handled/awaited.
Why is this bad? ​
Misused promises can cause crashes or other unexpected behavior, unless there are possibly some global unhandled promise handlers registered.
Examples ​
Examples of incorrect code for this rule:
ts
// Promises in conditionals:
const promise = Promise.resolve("value");
if (promise) {
// Do something
}
// Promises where `void` return was expected:
[1, 2, 3].forEach(async value => {
await fetch(`/${value}`);
});
// Spreading Promises:
const getData = () => fetch("/");
console.log({ foo: 42, ...getData() });Examples of correct code for this rule:
ts
// Awaiting the Promise to get its value in a conditional:
const promise = Promise.resolve("value");
if (await promise) {
// Do something
}
// Using a `for-of` with `await` inside (instead of `forEach`):
for (const value of [1, 2, 3]) {
await fetch(`/${value}`);
}
// Spreading data returned from Promise, instead of the Promise itself:
const getData = () => fetch("/");
console.log({ foo: 42, ...(await getData()) });Configuration ​
This rule accepts a configuration object with the following properties:
checksConditionals ​
type: boolean
default: true
Whether to check if Promises are used in conditionals. When true, disallows using Promises in conditions where a boolean is expected.
checksSpreads ​
type: boolean
default: true
Whether to check if Promises are used in spread syntax. When true, disallows spreading Promise values.
checksVoidReturn ​
type: object | boolean
checksVoidReturn.arguments ​
type: boolean
default: true
Whether to check Promise-returning functions passed as arguments to void-returning functions.
checksVoidReturn.attributes ​
type: boolean
default: true
Whether to check Promise-returning functions in JSX attributes expecting void.
checksVoidReturn.inheritedMethods ​
type: boolean
default: true
Whether to check Promise-returning methods that override void-returning inherited methods.
checksVoidReturn.properties ​
type: boolean
default: true
Whether to check Promise-returning functions assigned to object properties expecting void.
checksVoidReturn.returns ​
type: boolean
default: true
Whether to check Promise values returned from void-returning functions.
checksVoidReturn.variables ​
type: boolean
default: true
Whether to check Promise-returning functions assigned to variables typed as void-returning.
How to use ​
To enable this rule in the CLI or using the config file, you can use:
bash
oxlint --type-aware --deny typescript/no-misused-promisesjson
{
"rules": {
"typescript/no-misused-promises": "error"
}
}