Angular Element is not removed and readded to the DOM properly

@kseamon

🐞 bug report

Affected Package

The issue is caused by package @angular/elements

Is this a regression?

No

Description

When an Angular Element is detached from the DOM and then re-attached, none of the event bindings work (see minimal reproduction for demo). I am a Google engineer and this is causing issues for us (internal bug filed here: http://b/168062117).

I talked to @kseamon about this and he thinks the issue is located in either of these 2 places:

angular/packages/elements/src/create-custom-element.ts

Line 219 in a69507a

disconnectedCallback(): void {

angular/packages/elements/src/component-factory-strategy.ts

Lines 109 to 125 in a69507a

    
           disconnect() { 
        
             this.runInZone(() => { 
        
               // Return if there is no componentRef or the component is already scheduled for destruction 
        
               if (this.componentRef === null || this.scheduledDestroyFn !== null) { 
        
                 return; 
        
               } 
        
               // Schedule the component to be destroyed after a small timeout in case it is being 
        
               // moved elsewhere in the DOM 
        
               this.scheduledDestroyFn = scheduler.schedule(() => { 
        
                 if (this.componentRef !== null) { 
        
                   this.componentRef.destroy(); 
        
                   this.componentRef = null; 
        
                 } 
        
               }, DESTROY_DELAY); 
        
             }); 
        
           }

Specifically, this.scheduledDestroyFn in not set to null in the scheduled destroy and so may be called again upon connect. I'm testing adding one line to see if it fixes the immediate issue.

However, even with this fix, there will still exist a tiny race condition that occurs when an element is scheduled to be destroyed and then connects before the destroy executes.

🔬 Minimal Reproduction

https://stackblitz.com/edit/angular-ovchwr?file=src%2Findex.html

🔥 Exception or Error

No user-visible exception

🌍 Your Environment

Angular Version:

I'm running it against the latest Angular in google3.

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🐞 bug report

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Description

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	disconnect() {
	this.runInZone(() => {
	// Return if there is no componentRef or the component is already scheduled for destruction
	if (this.componentRef === null \|\| this.scheduledDestroyFn !== null) {
	return;
	}

	// Schedule the component to be destroyed after a small timeout in case it is being
	// moved elsewhere in the DOM
	this.scheduledDestroyFn = scheduler.schedule(() => {
	if (this.componentRef !== null) {
	this.componentRef.destroy();
	this.componentRef = null;
	}
	}, DESTROY_DELAY);
	});
	}

Description

🐞 bug report

Affected Package

Is this a regression?

Description

🔬 Minimal Reproduction

🔥 Exception or Error

🌍 Your Environment

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

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