[Components]: Fix race condition in tree reload handling

[MartynasStrazdas]

A Flaky test (detects a change in rule condition) appeared when we switched to react 19, because of slight differences how react runs effects.

From my understanding the test fails because setting a variable trigger a reload, which produces a new modelSource React then re-runs the useEffect - removing the old listener and adding a new one. If the next variable change fires in the gap between removal and re-subscription, the event is lost and the test hangs.

Underlying issue was race condition in how tree reload is handled. It was possible for change event to be raised between listener is removed and added back. This meant that some events were missed and tree was not reloading.

[changeset-bot]

🦋 Changeset detected

Latest commit: c6d66d7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@itwin/presentation-components	Patch

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[saskliutas]

Looks like we need to wait for tree to actually reload (nodeLoader/modelSource) to change? d2c7082

[MartynasStrazdas]

Looks like we need to wait for tree to actually reload (nodeLoader/modelSource) to change? d2c7082

Seems to fix the issue, can you push that commit here?

[saskliutas]

Looks like we need to wait for tree to actually reload (nodeLoader/modelSource) to change? d2c7082

Seems to fix the issue, can you push that commit here?

Pushed

[Copilot]

Pull request overview

This PR stabilizes the Tree update full-stack test under React 19 by ensuring assertions wait for the hook to produce a new nodeLoader before verifying the updated tree, accounting for changed effect scheduling.

Changes:

• Track the last observed nodeLoader and wait for it to change before asserting the updated hierarchy.
• Update the verification loop to advance the tracked nodeLoader after each successful update.

[grigasp]

A Flaky test appeared when we switched to react 19, because of slight differences how react runs effects.

Can we have more details on this?

• which test is that
• do we have a failure log? E.g. what exactly failed