PrimeNG p-table Virtual Scroll and Angular OnPush Change Detection Interoperability

Direct Answers

1. Immutable array reference update: In a standard zoned Angular application, replacing the [value] input with a new array reference does trigger Angular's OnPush change detection for the host component, which in turn causes the p-table to re-evaluate its virtual scroll and refresh the viewport. No manual ChangeDetectorRef call is required for this basic case.
2. Manual mark-for-check: Not required after every data replacement when running inside NgZone. However, if the data update occurs outside NgZone (e.g., in a WebWorker, setTimeout with NgZone.runOutsideAngular, or Angular v18+ experimental zoneless change detection), the OnPush component will not be checked automatically. In those scenarios you must call markForCheck() or detectChanges() on the host component.
3. Consistency across PrimeNG v16–v18: Not guaranteed. v16 had known issues where virtual scroll retained stale row heights after data replacement. v17 introduced fixes but still occasionally required explicit detectChanges(). v18 further stabilizes the ngOnChanges handling, yet zoneless support remains experimental and may introduce timing differences.

Why It Works (Confirmed Behavior)

• Angular's OnPush strategy checks a component when any @Input reference changes. Passing a new array to [value] satisfies this condition.
• PrimeNG's TableVirtualScroll recalculates visible rows during the change detection cycle (inside ngOnChanges or ngDoCheck). The component does not listen for array mutations; it relies solely on input reference changes.
• In a zoneless context, Angular does not schedule change detection automatically after async events, so the OnPush component remains unchecked until explicitly marked.

Likely Explanations (Not Fully Verified)

• PrimeNG v18's ngOnChanges now resets the virtual scroll calculator more reliably, reducing the need for manual intervention.
• Scroll position preservation after data replacement is version-dependent; the table may reset to the top in some versions.
• If the p-table is nested inside another OnPush component, the parent must also receive a new reference or be marked for check.

Verification Steps for Your Environment

1. Create a minimal Angular component with ChangeDetectionStrategy.OnPush and a p-table with virtualScroll.
2. Add a button that replaces the data array with a new reference (e.g., this.data = [...newData]).
3. Observe whether the viewport updates without calling ChangeDetectorRef methods.
4. Repeat the test after bootstrapping with provideExperimentalZonelessChangeDetection() to see if manual markForCheck() becomes necessary.
5. Check the PrimeNG changelog for v16, v17, v18 for entries related to "virtual scroll", "OnPush", or "change detection".

One Diagnostic Detail That Changes the Recommendation

Are you running with Angular's experimental zoneless change detection (provideExperimentalZonelessChangeDetection()) or deliberately updating data outside NgZone? If yes, manual markForCheck() is required. If no, the immutable reference update is sufficient.

Safe Pattern

// Inside an OnPush component
updateData(newItems: Item[]) {
  this.data = [...newItems]; // new reference
  // Only needed if update runs outside NgZone or in zoneless mode:
  // this.cdr.markForCheck();
}