Fix class inheritance in IE <=10 (T3041) #3527
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danez
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Interesting idea. Right now IE9/10 would be expected to use loose-mode to avoid this issue, but you are right this may be another approach. |
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The problem with loose-mode for us is that we are not always in control how projects transpile their code. In the concrete example of babylon (which we use in the browser for our internal styleguide) we can't control the transpiling configuration it uses (currently it uses babel6 non-loose since v6.8). |
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| this.isStatic ? this.getObjectRef() : t.memberExpression(this.getObjectRef(), t.identifier("prototype")) | ||
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| t.logicalExpression( |
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Maybe worth making a simple helper function for this?
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I extracted the logic into a helper within babel-helper-replace-supers
I would have liked to share this method also with the transform-class package, but not sure where to put the helper function then.
Current coverage is 87.44%@@ master #3527 diff @@
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danez
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PR: Bug Fix 🐛
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Any progress on this? Both loose mode and "broken on IE 9 and 10" aren't fun places to be :-( |
Internet Explorer 9&10 do not support __proto__ at all, don't have Object.setPrototypeOf(), but have Object.getPrototypeOf(). Because of this setting the prototype is not possible, which makes the babelHelpers.inherits() function to set __proto__ although not supported. Afterwards Object.getPrototypeOf() is used, but this one is not respecting the "custom" property __proto__ that we set. The solution is to check for __proto__ first and afterwards fallback to Object.getPrototypeOf().
Fixes facebook#6929 See babel/babel#3527 for more details
We use Babel 6.26.0, which has been patched for this already; see babel/babel#3041 and babel/babel#3527
We use Babel 6.26.0, which has been patched for this already; see babel/babel#3041 and babel/babel#3527
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Hello, Class inheritance does not work again in Any plans for IE9/10 supporting? |
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Problem summary
Internet Explorer 10 and below do not support
__proto__at all, they don't haveObject.setPrototypeOf(), but they haveObject.getPrototypeOf().When babel is doing the inheritance it is trying to use
Object.setPrototypeOf()if this function is available. As mentioned this function isn't available (even with core-js, as also core-js can't polyfill this). In this case the helper falls back to just set__proto__on the object. For IE <=10 this is just some custom property that gets set on the target, with no special meaning.In the constructor after the inherit helper finished its work, babel uses
Object.getPrototypeOf()to get the prototype. This is supported by IE, but as babel can't set the prototype on the target, this will just return the base Object-prototype and not the wanted superclass.Proposed solution
The solution simply changes the retrieval of the prototype by first trying to get
__proto__and if not available falling back toObject.getPrototypeOf(). This fixes the behavior in IE as babel reads the custom prop__proto__that the inherit helper was setting. In all other browsers this should not have any effect, as__proto__should be the same asObject.getPrototypeOf().Does anyone see a problem with this solution? Anything that I maybe have missed?
P.S.: I did not yet change any of the tests, as I wanted to get feedback first on the solution.