fix(grid): Setup columns when autoGenerate is set after the grid data

[mddragnev]

Closes #16830

Type of Change (check all that apply):

• Bug fix
• New functionality
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes)
• Documentation
• Demos
• CI/CD
• Tests
• Changelog
• Skills/Agents

How Has This Been Tested?

• Unit tests
• Manual testing
• Automated e2e tests

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them
• Accessibility (ARIA, keyboard navigation, focus management) has been verified

[Copilot]

Pull request overview

This PR addresses a grid rendering issue where setting data first and then enabling autoGenerate after initialization results in no data being rendered (issue #16830).

Changes:

• Adds ngOnChanges handling in IgxGridBaseDirective to call setupColumns() when autoGenerate is enabled after data is already present.
• Adjusts some derived grid components to explicitly override ngOnChanges.
• Adds a unit test covering the “data first, autoGenerate later” scenario.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
projects/igniteui-angular/grids/pivot-grid/src/pivot-grid.component.ts	Marks ngOnChanges as override in pivot grid.
projects/igniteui-angular/grids/hierarchical-grid/src/row-island.component.ts	Marks ngOnChanges as override in row island.
projects/igniteui-angular/grids/grid/src/grid.component.spec.ts	Adds a unit test for toggling autoGenerate after setting data.
projects/igniteui-angular/grids/grid/src/grid-base.directive.ts	Implements OnChanges, wires autoGenerate via @WatchChanges, and triggers setupColumns() on relevant changes.
projects/igniteui-angular/grids/core/src/watch-changes.ts	Tweaks WatchChanges to avoid calling ngOnChanges when _init is undefined.

Comments suppressed due to low confidence (2)

projects/igniteui-angular/grids/pivot-grid/src/pivot-grid.component.ts:1028

• This ngOnChanges now overrides a base implementation (IgxGridBaseDirective.ngOnChanges). Since it doesn’t call super.ngOnChanges(changes), any base change-handling (including the new autoGenerate handling) will be skipped for the pivot grid. Consider calling super.ngOnChanges(changes) to preserve base behavior and future-proof overrides.

    public override ngOnChanges(changes: SimpleChanges) {
        if (changes.superCompactMode && !changes.superCompactMode.isFirstChange()) {
            this._shouldUpdateSizes = true;
            resizeObservable(this.verticalScrollContainer.displayContainer).pipe(take(1), takeUntil(this.destroy$)).subscribe(() => this.resizeNotify.next());
        }
    }

projects/igniteui-angular/grids/hierarchical-grid/src/row-island.component.ts:475

• This ngOnChanges now overrides a base implementation (IgxGridBaseDirective.ngOnChanges). Since it doesn’t call super.ngOnChanges(changes), any base change-handling (including the new autoGenerate handling) will be skipped for IgxRowIslandComponent. Consider calling super.ngOnChanges(changes) before emitting layoutChange so base behavior is preserved.

    public override ngOnChanges(changes) {
        this.layoutChange.emit(changes);
        if (!this.isInit) {
            this.initialChanges.push(changes);
        }