React emit should have an '_extends' helper for spread attributes

This is effectively a polyfill for Object.assign, and we should consider emitting the specific helper.

can you elaborate on the request, and why?

We currently emit a call to React.__spread which has been deprecated for a while now (and might be gone soon?). The official JSX transformer calls _extends which is initialized with Object.assign || (object.assign polyfill)

__spread is gone in react 15.0. which means typescript 1.8.9 cannot compile TSX with react 15.0.

My workaround:

import {assign} from 'lodash';
(React as any).__spread = assign;

Workaround without lodash: #7270 (comment)

Nicolas Goy (@kuon)

Nicolas Goy (@kuon) Thank you for the workaround.
I would suggest using object-assign npm module directly. It is what React uses in 15.

Yeah, but as I had lodash in my project, with typescript definition and all, it was easier.

We’ll temporarily bring it back to avoid breaking everyone using TS: react/react#6444. However the method is deprecated and will go away in the next major release.

dan (@gaearon)

Thanks so much dan (@gaearon), we really appreciate the temporary rollback.

Proper workaround without lodash:

In a *.d.ts file, add:

declare module 'object-assign' {
    function Assign(target: any, source: any): any;
    module Assign { }
    export = Assign;
}

In your main *.ts file, reference your lib file and add:

import * as assign from 'object-assign';
(React as any).__spread = assign;

For clarity, you might want to add object-assign as an explicit dependency in your package.json until this is fixed.

A fix is out in #7952. Ideally we can get the change into the next nightly.

Just in case someone else wonders, ES6 Object.assign works as well:

(React as any).__spread = Object.assign;

(but you need core-js or another polyfill if you're not targeting ES6).

A fix should be out in our nightlies tonight. We'll potentially port the fix to our 1.8 branch.

This should be fixed in TypeScript 1.8.10, which is now on npm and NuGet.

Now that we have this for react, how about getting this for normal TypeScript (primarily because libraries out there e.g. redux love it) {...foo,{withSomethingMore}}

: #2103 🌹

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React emit should have an '_extends' helper for spread attributes #7270

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React emit should have an '_extends' helper for spread attributes #7270

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mhegazy commented on Feb 26, 2016

RyanCavanaugh commented on Feb 26, 2016

kuon commented on Apr 7, 2016

gaearon commented on Apr 7, 2016

kuon commented on Apr 7, 2016

gaearon commented on Apr 7, 2016

DanielRosenwasser commented on Apr 7, 2016

kuon commented on Apr 7, 2016

DanielRosenwasser commented on Apr 8, 2016

jgillich commented on Apr 8, 2016

DanielRosenwasser commented on Apr 8, 2016

DanielRosenwasser commented on Apr 12, 2016

basarat commented on Apr 13, 2016

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