fix(form): route Ctrl+Enter through onSubmit and stop double-firing on_change

[Mystery01092000]

Summary

Fixes three related submit-inconsistency bugs in mo.ui.form reported in #8324.

Bug 1 — Ctrl+Enter bypassed onSubmit

FormPlugin.tsx called setValue(newValue) directly in the onKeyDown handler, skipping the <form>'s onSubmit. This meant shouldValidate and clearOnSubmit were silently ignored when using the keyboard shortcut.

Fix: Replace setValue(newValue) with formDiv.current?.requestSubmit(), which routes the keyboard shortcut through the same onSubmit path as the button click.

Bug 2 — Shift+Enter bypassed the form wrapper

OnBlurredInput's onKeyDown in input.tsx fired setValue on any Enter keypress with no modifier check. Shift+Enter inside a wrapped text input would commit the input value directly, completely bypassing the form's buffering layer.

Fix: Add a shiftKey guard — only plain Enter (no Shift) commits the value.

Bug 3 — Wrapped element's on_change fired twice per submission

form._convert_value() called element._update(value), which always triggers the element's _on_change callback. This caused the wrapped element's on_change to fire unexpectedly during form submission (in addition to the form's own on_change).

Fix: Add UIElement._update_value() — identical to _update() but without the _on_change call. form._convert_value() now calls _update_value() so the wrapped element's on_change only fires when the element itself is interacted with, not when the form extracts its submitted value.

Files changed

File	Change
frontend/src/plugins/impl/FormPlugin.tsx	requestSubmit() instead of direct setValue() in onKeyDown
frontend/src/components/ui/input.tsx	shiftKey guard in OnBlurredInput.onKeyDown
marimo/_plugins/ui/_core/ui_element.py	New _update_value() method (silent update, no callback)
marimo/_plugins/ui/_impl/input.py	form._convert_value uses _update_value not _update
frontend/src/plugins/impl/__tests__/FormPlugin.test.tsx	New test file covering all three fixes
tests/_plugins/ui/_impl/test_input.py	Three new regression tests for the Python-side fix

Test plan

• Ctrl+Enter triggers validation when shouldValidate=True
• Ctrl+Enter clears inputs when clearOnSubmit=True
• Shift+Enter inside a text input does not submit the form
• Submit button calls setValue exactly once
• Wrapped element's on_change does not fire on form submission
• Form's on_change fires exactly once per submission
• _update_value() updates value without triggering on_change

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Note: Please let me know if any adjustments are needed to match the project's style or conventions. I'm happy to iterate.

I have read the CLA Document and I hereby sign the CLA

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Mar 29, 2026 5:11pm

[github-actions]

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[Mystery01092000]

I have read the CLA Document and I hereby sign the CLA

[Mystery01092000]

recheck

[manzt]

I pulled this down and tested locally but wasn't able to verify that Bug 3 (the double-fire) is fixed. Wrapping a mo.ui.text(on_change=...) in a form and submitting still fires the element's on_change.

Have you verified these change yourself? Could you share a screen recording or a minimal repro snippet showing the correct behavior?

[mscolnick]

Going to move to draft while it needs changes.