fix timing issue to apply edits after data has come in

[Light2Dark]

📝 Summary

Closes #8024. There was a timing issue where the edits are applied even when data is empty, hence they are not applied.

🔍 Description of Changes

📋 Checklist

• I have read the contributor guidelines.
• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• Tests have been added for the changes made.
• Documentation has been updated where applicable, including docstrings for API changes.
• Pull request title is a good summary of the changes - it will be used in the release notes.

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Project	Deployment	Review	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jan 28, 2026 10:18am

[Copilot]

Pull request overview

This pull request fixes a timing issue in the data editor where edits were being applied before data had loaded, resulting in edits not being applied at all. The fix changes from using useOnMount to using useEffect with dependencies on data.length and edits, and adds a ref to track whether edits have been applied.

Changes:

• Replaced useOnMount with useEffect to apply edits only after data has loaded
• Added hasAppliedEdits ref to prevent re-applying edits on subsequent renders
• Moved columns definition before the edit-application logic (required for the effect to access it)
• Removed a TODO comment about old edits

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
frontend/src/plugins/impl/data-editor/glide-data-editor.tsx	Replaced useOnMount with useEffect to fix timing issue when applying initial edits, added ref to track application state, and reorganized code
frontend/src/plugins/impl/DataEditorPlugin.tsx	Removed TODO comment about old edits

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[Copilot]

The condition data.length === 0 prevents the effect from running when data is empty. However, this also prevents processing edits that add new rows to an initially empty dataset (see lines 149-157 which handle edit.rowIdx >= data.length). If a user starts with an empty dataset and has edits that add rows, those edits won't be applied. Consider using a separate loading state flag or checking if data has been initialized, rather than relying solely on data.length.

Suggested change

	// Apply initial edits after data has loaded
	useEffect(() => {
	// Don't apply if already applied or data hasn't loaded yet
	if (hasAppliedEdits.current || data.length === 0) {
	return;
	}
	// Apply initial edits once
	useEffect(() => {
	// Don't apply if:
	// - Already applied edits
	// - No edits to apply
	if (hasAppliedEdits.current || edits.length === 0) {

[github-actions]

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.19.7-dev31