ngOnChanges produces changes for every input, even when the objects are unchanged.

[Jrubzjeknf]

Problem: ngOnChanges seems to always provide all inputs in the SimpleChanges object, even though some inputs are unchanged. Correct behavior would be that only the changed inputs are provided, similar to the Angular implementation.

Repro steps:

• Open stackblitz
• Click on val1 button, which changes the someValue property on HelloComponent.
• Notice in the console that the following SimpleChanges object is generated. The issue is that name should not come up as a change, since it has not changed.

{
  "name": {
    "previousValue": "World",
    "currentValue": "World",
    "firstChange": false
  },
  "someValue": {
    "previousValue": "myvalue",
    "currentValue": "val1",
    "firstChange": false
  }
}

My own debugging shows that all bound input properties are always marked as changed. I can work around it for now by checking for equality myself in the ngOnChanges method of my component, but a fix would of course be preferable.

[gund]

Thanks for reporting this issue!
It does look like it's creating changes for unchanged inputs which is super weird as it did not do it before...

I will investigate what is the cause and fix it soon.

[gund]

Okay so after my investigation I figured out that this is a regression in Angular's KeyValueDiffer Service that this library uses in order to figure out the changes in inputs - it basically reports all properties to be changed even if just one property in object was changed...

I'm not sure if this was a change by design or a regression in Angular so I'm going to open an issue there and ask for clarification.

After their response we will know how to address this bug but for now I would recommend you to simply do a reference checks in OnChanges hook manually.

[gund]

During deeper investigation is turns out that Angular's differ works fine and library was using incorrect API to collect changes from it.

Currently new records are collected from forEachAddedItem() method and changed records from forEachItem() method which always returns all items despite any changes (which is logical).
See:

ng-dynamic-component/projects/ng-dynamic-component/src/lib/io/io.service.ts

Lines 241 to 245 in a4dd160

	private _collectChangesFromDiffer(differ: KeyValueChangesAny): SimpleChanges {
	const changes = {} as SimpleChanges;
	differ.forEachAddedItem(recordToChanges(changes));
	differ.forEachItem(recordToNewChanges(changes));

But there is another method forEachChangedItem() that returns only changed records and behaves correctly.
See demo https://stackblitz.com/edit/angular-keyvalue-differ?file=src%2Fapp%2Fapp.component.ts

So I'm preparing a fix now and will release soon.
Thanks again for the reported bug with reproduction demo!

[Jrubzjeknf]

Thanks for your quick investigation and solution! Awesome to see that this package is so well supported. 😊

Will the change also be pushed to the @no-barrels tag? Apparently I need the package from that tag to build with Ivy.

[gund]

🎉 This issue has been resolved in version 7.0.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[gund]

Also it was released on @no-barrels tag!