internal: Make the Demo Form Accept Extra on_submit Handlers

[amsraman]

All Submissions:

• Have you followed the guidelines stated in CONTRIBUTING.md file?
• Have you checked to ensure there aren't any other open Pull Requests for the desired changed?

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

New Feature Submission:

• Does your submission pass the tests?
• Have you linted your code locally prior to submission?

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

After these steps, you're ready to open a pull request.

a. Give a descriptive title to your PR.

b. Describe your changes.

c. Put `closes #XXXX` in your comment to auto-close the issue that your PR fixes (if such).

[greptile-apps]

Greptile Summary

This PR exposes an on_submit parameter on demo_form and demo_form_dialog so callers can append extra event handlers after the built-in PostHog-tracking and dialog-close handlers.

• Both public functions (demo_form, demo_form_dialog) gain an on_submit: EventType[dict[str, Any]] | None parameter, properly documented and typed.
• The handler is normalised into a list via an isinstance(on_submit, list) check, then spread into the existing on_submit list after the two built-in handlers.

Confidence Score: 3/5

The change is small and well-scoped, but the handler-normalisation logic only recognises Python lists, so callers who pass a tuple of handlers will have their handlers silently mis-applied.

The normalization expression uses isinstance(on_submit, list) to detect multi-handler input, but Reflex also accepts tuples as multi-handler sequences. A tuple passed here skips the branch and gets wrapped as a single element, meaning the individual handlers inside it are never registered separately — a silent functional failure for any caller who uses tuple syntax.

packages/reflex-components-internal/src/reflex_components_internal/blocks/demo_form.py — specifically the extra_on_submit normalisation block (lines 294–296).

Important Files Changed

Filename	Overview
packages/reflex-components-internal/src/reflex_components_internal/blocks/demo_form.py	Adds optional on_submit pass-through to both demo_form and demo_form_dialog; the list-normalization logic doesn't handle tuples, which Reflex accepts as multi-handler sequences.

Sequence Diagram

sequenceDiagram
    actor User
    participant Form as rx.el.form
    participant PostHog as DemoFormStateUI.track_demo_form_posthog
    participant Dialog as demo_form_open_cs (ClientState)
    participant Extra as extra_on_submit handlers

    User->>Form: Submit
    Form->>PostHog: on_submit[0] — PostHog track
    PostHog-->>Form: done
    Form->>Dialog: on_submit[1] — set_value(False) → close dialog
    Dialog-->>Form: done
    Form->>Extra: on_submit[2..n] — caller-provided handlers
    Extra-->>Form: done

Loading

_{Reviews (1): Last reviewed commit: "Internal Demo Form accepts extra on_subm..." | Re-trigger Greptile}

[greptile-apps]

isinstance check doesn't handle tuple event-handler lists

Reflex allows event handler collections to be passed as either a list or a tuple. If a caller passes on_submit as a tuple (e.g., on_submit=(HandlerA, HandlerB)), isinstance(on_submit, list) returns False, so the entire tuple is wrapped in another list as a single element — meaning *extra_on_submit spreads (HandlerA, HandlerB) as one item instead of two separate handlers. Reflex would then try to interpret the tuple as a single handler and likely raise a runtime error or silently ignore it.

Suggested change

	extra_on_submit = (
	on_submit if isinstance(on_submit, list) else [on_submit] if on_submit else []
	)
	extra_on_submit = (
	list(on_submit)
	if isinstance(on_submit, (list, tuple))
	else [on_submit]
	if on_submit
	else []
	)

[amsraman]

tuples aren't accepted as part of that type, right?

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks
⏩ 2 skipped benchmarks¹

---

_{Comparing aditya/demo-form-extra-submit (e6e249e) with main (56da91a)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩