Flow: Sealing Objects when using spread or Object.assign

Created on 16 May 2016 · 10Comments · Source: facebook/flow

It would be great to be able to keep an object sealed somehow when using spread or Object.assign.

The use case I'm thinking of is for redux inside a reducer.
Currently if I misspell the key name in an update, flow can't check it as it just thinks it's an extra property to an object.

feature request

Source

kristian-puccio

👍9

Most helpful comment

Any news on the matter?

mmazzarolo on 2 Mar 2017

👍4

All 10 comments

The new exact object types should help here.

ianobermiller on 18 Oct 2016

😕1

@ianobermiller It seems that sealed objects/exact object types are still not compatible with the spreading operator.

```javascript
/* @flow */
type State = {|
username: ?string,
password: ?string
|}

const state: State = {
username: null,
password: null
}

const validState:State = state
const invalidState:State = { ...state } // flow-error: Inexact type is incompatible with exact type object type
```
Do you know if there are any plan on supporting this feature?
It's a really common use pattern in redux reducers.

Thank you in advance 👍

@kristian-puccio did you find any alternative way to handle this issue?

mmazzarolo on 22 Dec 2016

👍3

No unfortunately still waiting on a solution.

On 23 December 2016 at 02:30, Matteo Mazzarolo notifications@github.com
wrote:

@ianobermiller https://github.com/ianobermiller It seems that sealed
objects/exact object types are still not compatible with the spreading
operator.

/* @flow */
type State = {|
username: ?string,
password: ?string|}
const state: State = {
username: null,
password: null
}
const validState:State = stateconst invalidState:State = { ...state } // object literal. Inexact type is incompatible with exact type object type

Do you know if there are any plan on supporting this feature?
It's a really common use pattern in redux reducers.

Thank you in advance 👍

@kristian-puccio https://github.com/kristian-puccio did you find any
alternative way to handle this issue?

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