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Console log WeakSet and WeakMap always empty #19001
Description
- Version: 8.9.4
- Platform: Windows 10 x64
- Subsystem: powershell
Currently trying to console.log WeakSet or WeakMap will always display as empty.
var set = new WeakSet([{yes: true}]);
console.log(set); // logs WeakSet{}
var map = new WeakMap([[{yes: true}, true]]);
console.log(map); // logs WeakMap{}I believe I understand why logging them does not work, but node should display a warning and/or should document this behavior.
Activity
devsnek commentedon Feb 26, 2018
related to #18227
BridgeAR commentedon Feb 26, 2018
This is language related and it is just not possible to inspect
WeakSet/WeakMap.We did not yet come to a conclusion how to handle this on the long term and I am going to write a summary of pro / con some time this week.
@anantoghosh what kind of warning would you expect? I can not think of a good way to display a warning in this case.
anantoghosh commentedon Feb 26, 2018
Maybe a message after using console.log()
"WARNING: WeakSet/WeakMap will always appear empty. See link"
Although simply mentioning this in the documentation would have been fine.
Currently, trying to google for this issue does not reveal any information.
bnoordhuis commentedon Feb 26, 2018
At least w.r.t. inspection it should be possible to add a V8 API to peek into them.
In fact, it already exists but not in any official capacity:
BridgeAR commentedon Feb 26, 2018
@bnoordhuis that is a very interesting point and opens new possibilities for the other discussion as well. The question for me though is: can this be implemented independent of the engine?
BridgeAR commentedon Mar 25, 2018
Support for inspecting WeakMap and WeakSet was added in master. The
showHiddenoption must be set to true and otherwise it will tell that the items were not inspected.