Fix objectSpread2 backward compatibility

[nicolo-ribaudo]

Q	A
Fixed Issues?	Fixes #10169
Patch: Bug Fix?	yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11055/

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11055/

[XhmikosR]

@nicolo-ribaudo: Using v7.5.1 still fails for us https://travis-ci.org/twbs/bootstrap/jobs/554971554

[nicolo-ribaudo]

It seems like there is a problem with the way rollup-plugin-babel injects the helpers. Can you try using @babel/plugin-transform-runtime and @babel/runtime instead? It should work until the rollup-plugin-babel problem is fixed.

Or you can also try forcing rollup to use @babel/helpers v7.5.0 by npm-installing it.

[benjamn]

I’m seeing the objectSpread helper injected as a function, even though I’m using @babel/plugin-transform-runtime:

function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { if (i % 2) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } else { Object.defineProperties(target, Object.getOwnPropertyDescriptors(arguments[i])); } } return target; }

Is that something y’all’re aware of?

[nicolo-ribaudo]

Did you tell @babel/plugin-transform-runtime which version of @babel/runtime you are using (using the version option)? Otherwise we must assume that it is ^7.0.0, and can't rely on helpers introduced in newer versions.

[billyjanitsch]

@nicolo-ribaudo FYI the version option is not documented in the runtime plugin docs. Would you like me to open an issue for that in the website repo?

Also, if the version option is incompatible with objectSpread2, shouldn't the effect of this PR be to fall back to importing the old objectSpread helper, rather than injecting the new objectSpread2 helper? In other words, it doesn't seem like the try/catch block added in this PR is working as intended.

[benjamn]

@nicolo-ribaudo That was the trick I needed, thanks!

@billyjanitsch I was just about to leave a similar comment about documentation. You have my full support for opening an issue.

[nicolo-ribaudo]

FYI the version option is not documented in the runtime plugin docs. Would you like me to open an issue for that in the website repo?

Thanks! I have opened babel/website#2055 in the meantime, but a PR would be appreciated 😊

Also, if the version option is incompatible with objectSpread2, shouldn't the effect of this PR be to fall back to importing the old objectSpread helper, rather than injecting the new objectSpread2 helper? In other words, it doesn't seem like the try/catch block added in this PR is working as intended.

The try-catch block is used when loading the v7.5 plugin with an older @babel/core version, which doesn't even know about the existence of objectSpread2.
If you are using @babel/core 7.5 the helper exists. @babel/transform-runtime inlines it because it's better to use an inline working helper, than a broken helper from @babel/runtime.