transform-object-rest-spread does not follow complete spec, should use CreateDataProperty instead of Set (T7461)

[babel-bot]

Issue originally made by @pitaj

Bug information

• Babel version: 6.9.1
• Node version: 6.2.2
• npm version: 3.9.5

Options

{
  plugins: ['transform-object-rest-spread', 'transform-es2015-destructuring']
}

Input code

const l = {
  a: 1,
  c: 3,
};

const k = {
  a: 0,
  b: 1,
  set c(val) { this._c = -6; },
  d: 3,
  e: 4,
  ...l,
};

assert.equals(k.c, 3);

Description

The spec for Object spread explicitly states that CreateDataProperty should be used instead of Set. Currently, the spread transform uses Object.assign, which uses Set.

This will cause instances where setters that exist on the target object will be triggered, even though that behavior is counter to spec. In cases where a setter is not detected within the surrounding object literal, _extends can be used. However, if a setter is detected, then a different function using Object.defineProperties should be used.

Alternatively, it could be specified that this transform does not fully comply with the specification, and setters within object literals should be avoided with this syntax.

[babel-bot]

Comment originally made by @loganfsmyth

I'm all for fixing this, but it does seem like this would likely have to wait for a future 7.x release.

[nicolo-ribaudo]

Fixed: https://babeljs.io/repl#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=MYewdgzgLgBANjAvDA3gKBjAhgLhgRgBoMZg8BmYgXwG401RJYBrJVE3GABmMwCM8REhACmsYAAoAbljgBKVDCgALAJYQAdAH1gbALQA2GjCq8YAEwpmReACxmNjuNTppZIgE5QJzDcDk0QA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=true&fileSize=false&timeTravel=false&sourceType=module&lineWrap=false&presets=&prettier=false&targets=&version=7.5.5&externalPlugins=%40babel%2Fplugin-proposal-object-rest-spread%407.5.5