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Change detection error -> infinite loop #4323
Description
I found a case where change detection enters an infinite loop on an error.
The code in question:
@Component({selector: "signup-comp"})
@View({
directives: [CORE_DIRECTIVES, FORM_DIRECTIVES],
template: `
<form #f="form" (ng-submit)='onSignUp(f.value)'>
<div ng-control-group='credentials' #credentials="form">
Login <input type='text' ng-control='login'>
Password <input type='password' ng-control='password'>
</div>
<div *ng-if="!d.valid">Credentials are invalid</div>
<div ng-control-group='personal'>
Name <input type='text' ng-control='name'>
</div>
<button type='submit'>Sign Up!</button>
</form>
`
})The key is the ng-if expression !d.valid. d is not defined, and this triggers an infinite loop.
Here is a full Plunker example.
Activity
alxhub commentedon Sep 23, 2015
It seems like
<div ng-control-group='credentials'></div>combined with theng-ifis enough to trigger the bug.alxhub commentedon Sep 29, 2015
I tracked down the root cause:
NgControlGroupdeclares anonInitmethod, which schedules some work to be completed asynchronously, viaPromiseWrapper.resolve.The problem is that
onInitcan actually be called multiple times - it is called if change detection runs and has never completed successfully. If an exception happens during change detection afteronInitis called,AbstractChangeDetector.alreadyCheckedwill not be set andonInitwill be run again during the next tick. SinceonInitinNgControlGroupschedules asynchronous work, that next tick will happen immediately, causing a crash loop.angular-automatic-lock-bot commentedon Sep 7, 2019
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