Bail on hiPri render on missing layout data before checking priority (#…

…41270)

Summary:
Pull Request resolved: #41270

`scheduleCellsToRenderUpdate()` is called in response to new measurements, or component changes. It has logic to decide whether to immediately calculate new state, or to defer it until a later batched period.

It will not immediately update state if we don't yet have measurements for cells, but this condition is after another which calculates priority, relying on these measurements. These are garbage if we don't yet have measurements, and trigger an invariant violation in horizontal RTL.

This switches around the conditions, to avoid offset resolution if we don't yet have valid measurements.

I suspect some "hiPri" renders where cells shift are bugged right now when we update state in response to content size change, before we have new corresponding cell layouts.

Changelog:
[General][Fixed] - Bail on hiPri render on missing layout data before checking priority

Reviewed By: yungsters

Differential Revision: D50791506

fbshipit-source-id: 8dbffc37edd2a42f7842c0090d344dcd6f3e3c6d

packages/virtualized-lists/Lists/VirtualizedList.js

@@ -1752,8 +1752,9 @@ class VirtualizedList extends StateSafePureComponent<Props, State> {
     // If this is triggered in an `componentDidUpdate` followed by a hiPri cellToRenderUpdate
     // We shouldn't do another hipri cellToRenderUpdate
     if (
+      (this._listMetrics.getAverageCellLength() > 0 ||
+        this.props.getItemLayout != null) &&
       this._shouldRenderWithPriority() &&
-      (this._listMetrics.getAverageCellLength() || this.props.getItemLayout) &&
       !this._hiPriInProgress
     ) {
       this._hiPriInProgress = true;