feat(ui): animate mosaic field messages by alexcarpenter · Pull Request #9756 · clerk/javascript

alexcarpenter · 2026-09-14T19:21:29Z

Description

Restores the height animation Mosaic field messages had in the legacy FormFeedback, using the headless useTransition data-attribute pattern the other Mosaic components follow.

Adds Field.Message, a container that measures whichever message is showing (via ResizeObserver) and transitions its own height to match. It grows when a message arrives, follows the text when the message changes, and collapses after it clears, so callers never conditionally mount a message.
Adds Field.Success, the positive counterpart to Field.Error, sharing one internal feedback part (icon + text, aria-describedby registration). When one replaces the other inside Field.Message, the outgoing message fades out absolutely positioned over the incoming one while the container height moves once from the old height to the new.
Field.Error and Field.Success keep the last message through the exit transition and unmount once animations finish; both expose data-open / data-closed / data-starting-style / data-ending-style plus the .cl-field-message, .cl-field-error, and .cl-field-success slot classes. Under prefers-reduced-motion the height snaps and only the message fades.
Field.Message is also the field's live region: it stays mounted with role='status', so a message that arrives while the user is in the control is announced politely, and a message in its exit transition is aria-hidden so only the incoming one is read. Callers pass role='alert' when a message must interrupt. aria-describedby on the control always points at the open message only.
Existing Mosaic call sites (destructive block, reverification panels, edit name and username dialogs) are wrapped in Field.Message.
Field.Message measures with a small local hook rather than useMeasure. It needs a node handed in from registration (the measured child changes on every swap) and a synchronous first read so the height variable lands in the same commit as data-starting-style; useMeasure attaches its own ref and waits for the first ResizeObserver callback. Teaching useMeasure to cover both, and moving this and the headless FlowRoot onto it, is a follow-up.
Swingset: the field page documents the new parts, the error example is wider so long messages no longer reflow, and a new "Success" example swaps a two-line error for a one-line success message.

Checklist

pnpm test runs as expected.
pnpm build runs as expected.
(If applicable) JSDoc comments have been added or updated for any package exports
(If applicable) Documentation has been updated

Type of change

vercel · 2026-09-14T19:21:36Z

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changeset-bot · 2026-09-14T19:21:37Z

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Latest commit: 58a20a0

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.changeset/mosaic-field-error-enter-animation.md
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packages/ui/src/mosaic/features/reverification/steps/reverification-password.tsx
packages/ui/src/mosaic/features/user-profile/user-profile-account-section/user-profile-add-phone.dialog.tsx
packages/ui/src/mosaic/features/user-profile/user-profile-account-section/user-profile-edit-name.dialog.tsx
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.changeset/mosaic-field-error-enter-animation.md

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📝 Walkthrough

Walkthrough

The Field component now provides Field.Message and Field.Success. Feedback elements register with the message container, which measures content and animates height and transitions. Error and success states share rendering logic and support ARIA updates. Existing consumers and stories now use Field.Message. Tests cover transitions, resizing, accessibility, cleanup, and delayed unmounting.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🔵 Low · up to becd0

The new animated feedback behavior is broadly covered, but an empty Fragment can still produce blank field feedback in a narrow case. Fix that edge case before merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 13.04% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 23 functions across 18 files. (1 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: animated Mosaic field messages.
Description check	✅ Passed	The description directly explains the new Field.Message and Field.Success components, message animations, accessibility behavior, call-site updates, and documentation changes.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 13.04% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 23 functions across 18 files. (1 skipped: 1 unsupported.)

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commit: 58a20a0

github-actions · 2026-09-14T19:26:33Z

API Changes Report

Generated by Break Check on 2026-09-15T17:21:51.235Z

Summary

Metric	Count
Packages analyzed	19
Packages with changes	0
🔴 Breaking changes	0
🟡 Non-breaking changes	0
🟢 Additions	0

No API Changes Detected

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In @.changeset/mosaic-field-error-enter-animation.md:
- Around line 1-2: Add a Changeset release entry for the `@clerk/ui` package with
a minor version bump, replacing the empty frontmatter so the new Field.Message
and Field.Success API receives a version and changelog entry.

In `@packages/ui/src/mosaic/components/field/field.context.tsx`:
- Around line 116-118: Update the effect around register so it tracks changes to
the rendered DOM node rather than only the stable element ref object. Use a
callback ref or state to detect node identity changes, re-registering the
current node when it changes while preserving the existing open/closed behavior
and cleanup.

In `@packages/ui/src/mosaic/components/field/field.test.tsx`:
- Line 418: Update the tests that override Element.prototype.getAnimations to
preserve the original property descriptor and restore it in afterEach, ensuring
cleanup runs even when assertions fail and existing implementations are not
deleted.

In `@packages/ui/src/mosaic/components/field/field.tsx`:
- Around line 200-202: Update hasMessage to recursively inspect React fragments
and their children, treating fragments containing only null or empty values as
having no message. Preserve the existing non-empty child detection so
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.changeset/mosaic-field-error-enter-animation.md
packages/swingset/src/stories/field.component.mdx
packages/swingset/src/stories/field.component.stories.tsx
packages/swingset/src/stories/otp.component.mdx
packages/ui/src/mosaic/blocks/destructive/destructive.tsx
packages/ui/src/mosaic/components/field/field.context.tsx
packages/ui/src/mosaic/components/field/field.styles.ts
packages/ui/src/mosaic/components/field/field.test.tsx
packages/ui/src/mosaic/components/field/field.tsx
packages/ui/src/mosaic/components/field/index.ts
packages/ui/src/mosaic/features/reverification/panels/reverification-backup-code.tsx
packages/ui/src/mosaic/features/reverification/panels/reverification-otp.tsx
packages/ui/src/mosaic/features/reverification/panels/reverification-password.tsx
packages/ui/src/mosaic/user-profile/user-profile-account-section/user-profile-edit-name.dialog.tsx
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Co-Authored-By: Claude <noreply@anthropic.com>

…property" This reverts commit 78fb5fc.

This reverts commit 29b84b5.

maxyinger

looooks gooooood

maxyinger · 2026-09-15T19:32:17Z

+    alignContent: 'start',
+    display: 'grid',


any purpose for this grid? looks like we're popping exiting animation out of flow?

maxyinger · 2026-09-15T19:34:15Z

+    },
+    marginTop: {
+      default: 0,
+      ':where(:not([data-open]), [data-starting-style])': `calc(-1 * ${ROOT_GAP})`,


ahh to account for the gap jump. nice.

maxyinger · 2026-09-15T19:43:24Z

+    transitionDuration: durationVars['--cl-duration-base'],
+    transitionProperty: 'opacity',
+    transitionTimingFunction: 'linear',


Sometimes I try to avoid these frames where they cut the content with different exiting or entering easings/delays/durations or adding a slight scale anim. more of a reach goal tho/might add too much flavor to it. Already feels nice with the gap jump accounted for ❤️

yeah, was toying around with a mask during reveal, but didn't land on anything solid. something to maybe polish in a future PR https://x.com/blvdmitry/status/2000860557298045163

ooo I like that. yea def a future improvement and not a blocker

maxyinger · 2026-09-15T19:47:06Z

+function useMessageHeight(active: HTMLElement | null) {
+  const [height, setHeight] = React.useState(0);
+
+  useSafeLayoutEffect(() => {
+    if (!active) {
+      return undefined;
+    }
+
+    const measure = () => setHeight(active.offsetHeight);
+    measure();
+
+    if (typeof ResizeObserver === 'undefined') {
+      return undefined;
+    }
+
+    const observer = new ResizeObserver(measure);
+    observer.observe(active);
+    return () => observer.disconnect();
+  }, [active]);
+
+  return height;
+}


this is basically what we're doing in the flow component right? I added a useMeasure in here. might have to update it to use offsetHeight. looks like I missed adopting it in the Flow component

austin fixed that here recently #9726

yea I'm just wondering if we should unify into a central useMeasure since they all basically do the same thing?

I have this one:
https://github.com/clerk/javascript/blob/main/packages/ui/src/mosaic/hooks/useMeasure.ts

but needs to be updated to mirror austin's fix for flow and adopted everywhere

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Comment thread packages/ui/src/mosaic/components/field/field.tsx

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alexcarpenter and others added 5 commits September 15, 2026 12:50

feat(ui): animate mosaic field messages

2f58a4d

Co-Authored-By: Claude <noreply@anthropic.com>

feat(ui): announce mosaic field messages from a polite live region

0cc3cbb

Co-Authored-By: Claude <noreply@anthropic.com>

fix(ui): register field messages through a callback ref

c9a0ffb

Co-Authored-By: Claude <noreply@anthropic.com>

chore(ui): type the field message ref callback

8f096dc

Co-Authored-By: Claude <noreply@anthropic.com>

fix(ui): wrap phone dialog errors in Field.Message

becd00c

Co-Authored-By: Claude <noreply@anthropic.com>

alexcarpenter force-pushed the carp/mosaic-field-error-animation branch from 2907223 to becd00c Compare September 15, 2026 16:52

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feat(ui): fade the clipped edge of animating field messages

29b84b5

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refactor(ui): drive the field message fade from a registered property

78fb5fc

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Revert "refactor(ui): drive the field message fade from a registered …

bd48b8e

…property" This reverts commit 78fb5fc.

Revert "feat(ui): fade the clipped edge of animating field messages"

58a20a0

This reverts commit 29b84b5.

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alexcarpenter merged commit 9565c9b into main Sep 15, 2026
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alexcarpenter deleted the carp/mosaic-field-error-animation branch September 15, 2026 20:00

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