fix: do not dispatch event on stopedit when editor loading

[ugur-vaadin]

Description

When a slow custom editor is used, quickly tabbing through the cells can cause a false positive on cell value change since the editor value is not updated yet at that point. This leads to firing unnecessary item-property-changed events.

This PR adds an editor loading check in _stopEdit in order to avoid firing the events. This is effectively the same as canceling the edit.

Fixes #6816

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/contributing/pr
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[tomivirkki]

We should fix the underlying issue of the value being read directly from the web component instance with Flow Custom editors. The issue also manifests like this even when the editor is no longer loading:

Kapture.2024-11-27.at.10.47.54.mp4

[tomivirkki]

We decided to treat the issue mentioned above as a separate topic. This change is overall an improvement to the current behavior and does fix what's described in vaadin/flow-components#6816 so let's merge it.

[vaadin-bot]

Hi @ugur-vaadin and @ugur-vaadin, when i performed cherry-pick to this commit to 24.4, i have encountered the following issue. Can you take a look and pick it manually?
Error Message:
Error: Command failed: git cherry-pick ea24ab2
error: could not apply ea24ab2... fix: do not dispatch event on stopedit when editor loading (#8232)
hint: After resolving the conflicts, mark them with
hint: "git add/rm ", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

[vaadin-bot]

This ticket/PR has been released with Vaadin 24.6.0.beta3 and is also targeting the upcoming stable 24.6.0 version.