@typescript-eslint/no-misused-spread

... in an object copies a value's own enumerable properties, and many values have none or the wrong ones. TypeScript accepts all of these:

Spread	What you get
A promise, a `Map` or a `Set` in an object	An empty object.
Another iterable in an object	Its own properties, not the values it yields.
An array in an object	The indexes as keys: `{ "0": .., "1": .. }`.
A function without properties in an object	An empty object. You probably meant to call it.
A class instance in an object	The fields, without the class's methods and getters.
A class in an object	Only its static properties.
A string in an array or a call	Code points, which splits an emoji made of several of them.

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-misused-spread" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"@typescript-eslint/no-misused-spread" = ["error", {
  allow = [], # list of strings or objects
}]

Examples#

example.ts3 problems

declare function loadUser(): Promise<{ name: string }>;
const roles = new Map([["admin", true]]);
const tags = ["new", "sale"];

const user = { ...loadUser() };
const access = { ...roles };
const labels = { ...tags };

example.tsNo problems

declare function loadUser(): Promise<{ name: string }>;
const roles = new Map([["admin", true]]);
const tags = ["new", "sale"];

const user = { ...(await loadUser()) };
const access = Object.fromEntries(roles);
const labels = [...tags];

A class instance loses its methods:

example.ts1 problem

class Cart {
  items: string[] = [];
  count() {
    return this.items.length;
  }
}

const copy = { ...new Cart() };

A string in an array:

example.ts1 problem

function letters(name: string) {
  return [...name];
}

Intl.Segmenter splits a string into the characters a reader sees:

example.tsNo problems

function letters(name: string) {
  return Array.from(new Intl.Segmenter().segment(name), part => part.segment);
}

Options#

Option	Default	What it does
`allow`	`[]`	Types you can spread. Each is a name, or an object that also says where the type comes from: `{ "from": "file", "name": .. }`, `{ "from": "lib", "name": .. }` or `{ "from": "package", "name": .., "package": .. }`.

Not reported with allow: ["Cart"]:

example.tswith { "allow": ["Cart"] }No problems

class Cart {
  items: string[] = [];
  count() {
    return this.items.length;
  }
}

const copy = { ...new Cart() };