fix: icon animation when updating toast.loading() to another type (#743)

[te-ing]

Fixes #743

Summary
Fix missing icon transition animation when updating a toast created with toast.loading() to another type (e.g. toast.success()) using the same id.

Previously, the success icon appeared instantly without the fade animation that works correctly with toast.promise().

⸻

Root Cause

The icon transition animation depends on the promise field:
• toast.promise() sets promise
• → adds data-promise='true' which triggers the CSS fade-in
• → keeps the loader in the DOM during type transitions
• toast.loading() did not set promise
• → loader was removed immediately on type change
• → success icon rendered without animation

⸻

Fix
Set promise: Promise.resolve() in toast.loading() so it reuses the existing animation path.

Single-line change in state.ts, no rendering logic changes required.

++
Added a Playwright test covering the toast.loading() → toast.success() transition to ensure the data-promise attribute is preserved for animation.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
sonner	Error		Apr 1, 2026 0:24am