`TypeError: Cannot read property 'isUserInCondition' of undefined(…)`
```
load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:176 TypeError: Cannot read property 'isUserInCondition' of undefined TypeError: Cannot read property 'isUserInCondition' of undefined(…)log @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:176handler @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:153fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:45fireWith @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:46fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:46track @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:153runScript @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:161checkCssHandles @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:161execute @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:162implement @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:168(anonymous function) @ VM851:1(anonymous function) @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:4globalEval @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:4iterate @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0oyf810:166
```
---
Very hard to reproduce, but I've seen it a few times.
Seems like `mw.popups.experiment` is sometimes not defined when `resources/ext.popups.core.js#mw.popups.getEnabledState` is invoked. Looking at extension.json:
* `ext.popups.core` has the script `resources/ext.popups.core.js` which calls `mw.popups.experiment.isUserInCondition`
* `ext.popups.experiment`
* has the script `resources/ext.popups.experiment.js` that defines `mw.popups.experiment.isUserInCondition`
* has `ext.popups.core` in its dependencies
* `ext.popups.targets.desktopTarget` which lists first `ext.popups.core` and then `ext.popups.experiment` in its dependencies
* `ext.popups.schemaPopups.utils` which lists first `ext.popups.experiment` and then `ext.popups.core` in its dependencies
* gets loaded from a hook
Looking at the code, if the `ext.popups.core` module is loaded before `mw.popups.experiment` it could cause the above error which might break the feature and interfere with event logging as the property `popupEnabled` uses `mw.popups.getEnabledState()` which uses `isUserInCondition`. If this required value was undefined this would lead to dropped events. (cc @Tbayer )