fix(kernel): calling super.property unexpectedly returns undefined
#1932
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When overriding a property, the `@jsii/kernel` creates a shadow property for the previous implementation. In order to preserve the existing implementation (whether the property is dynamic or not), the property descriptor is retrieved and re-declared with the new name. This process did not crawl up the prototype chain, and only looked at the object itself. In many cases, this will never return anything (since `Object.getOwnPropertyDescriptor` will not return inherited descriptors) and in this case the `undefined` value was always used. This would break whenever attempting to override a property that was inherited from a parent class, and appears to fail with certain `node` runtimes where the dynamic properties are set on the object's prototype and not on the object itself. This change adds the necessary logic to traverse the prototype chain all the way up to `Object` (not included), to locate the property descriptor and upon failing to identify one, uses the current value of the property instead of `undefined`.
RomainMuller
added
bug
MrArnoldPalmer
approved these changes
Aug 21, 2020
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Thank you for contributing! ❤️ I will now look into making sure the PR is up-to-date, then proceed to try and merge it! |
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Merging (with squash)... |
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When overriding a property, the
@jsii/kernelcreates a shadow propertyfor the previous implementation. In order to preserve the existing
implementation (whether the property is dynamic or not), the property
descriptor is retrieved and re-declared with the new name.
This process did not crawl up the prototype chain, and only looked at
the object itself. In many cases, this will never return anything (since
Object.getOwnPropertyDescriptorwill not return inherited descriptors)and in this case the
undefinedvalue was always used.This would break whenever attempting to override a property that was
inherited from a parent class, and appears to fail with certain
noderuntimes where the dynamic properties are set on the object's prototype
and not on the object itself.
This change adds the necessary logic to traverse the prototype chain all
the way up to
Object(not included), to locate the property descriptorand upon failing to identify one, uses the current value of the property
instead of
undefined.This was the cause of aws/aws-cdk#9822
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.