feat: add the <bones-boundary> element (BON-3) - #34
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hunterbecton merged 12 commits intoAug 24, 2026
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Hook-free wrapper around <bones-boundary> for src/react/index.ts. onbones:show/onbones:hide bound as React 19 custom-element event listeners and were called in tests as expected, so no ref-based fallback was needed.
React 19 owns any prop it renders. A <BonesBoundary> that goes from `force` to `busy` makes React delete the aria-busy and inert it wrote for `force`, and the element had no way to notice: it ended up showing with no skeleton and an interactive subtree. The element now observes both output attributes and writes them back while it is showing or draining. It leaves them alone when it is idle, and its own hide is not something it fights. A view transition runs its update callback a frame or more later, so #hide setting the state to idle up front left a window where busy or force could show bones again and then have the queued update strip them anyway. #hide now moves to a fifth state, "hiding", and the update bails unless the element is still in it. busy and force during that window go back to showing with no second bones:show, and an element removed during it fires nothing. Two smaller fixes ride along. connectedCallback replays own properties left behind by a script that ran before the module loaded, so `boundary.busy` set early no longer shadows the accessor for good. A tag name that is already taken now warns instead of registering nothing in silence.
BonesBoundaryProps allowed id, className, style, ref, children, and data-*, and nothing else. `role`, `hidden`, `tabIndex`, `title`, `onClick`, and every aria-* attribute were type errors on an element whose whole job is to wrap real content. ElementAttributes now extends HTMLAttributes<HTMLElement> and keeps the element's own attributes on top. The wrapper also sets suppressHydrationWarning. When hydration lands later than `delay`, which is what selective hydration inside a streaming Suspense boundary does, the element has already written aria-busy and inert, and React reports the extra attributes as a mismatch. They are the element's to write, so React has no business diffing them. `ref` is now typed as Ref<BonesBoundary> through a type-only import of the element class. Types are erased at build time, so dist/react/index.mjs still imports nothing but react.
The usage snippet drove the boundary from a classic inline script, which runs before the deferred module import above it and touches an element that has not upgraded. It is a module script now, and it awaits customElements.whenDefined() before it reads or writes anything. The rest of the page fills gaps the review found: a new delay or min-duration applies to the next transition rather than the one running, inert blurs focus inside the boundary and nothing restores it, bones:show also fires when an element upgrades with server-rendered aria-busy, React does not own the attributes the element writes, and a project with its own bones-boundary declaration in JSX.IntrinsicElements will hit a conflict. Both READMEs now say that the bare specifier in the "Without React" snippet needs a bundler or an import map, and where to find the CDN form.
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughAdds the ChangesBoundary element
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR adds the bones-boundary loading element and React wrapper with delayed, accessible busy-state behavior; no actionable merge-blocking risk remains after normal checks and review. Sequence Diagram(s)sequenceDiagram
participant Application
participant BonesBoundary
participant Timer
participant ViewTransitionAPI
Application->>BonesBoundary: Set loading properties
BonesBoundary->>Timer: Schedule show or hide
Timer-->>BonesBoundary: Run transition callback
BonesBoundary->>Application: Update aria-busy, inert, and lifecycle events
BonesBoundary->>ViewTransitionAPI: Hide content when enabled
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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Inline comments:
In `@apps/docs/content/docs/api/bones-boundary.mdx`:
- Line 124: Update the React ownership description to state that when force is
true, the wrapper renders aria-busy and inert, so React owns and may remove them
during later prop updates; retain that the element restores those attributes
while it is showing bones.
In `@packages/bones/src/element/boundary.ts`:
- Around line 108-122: Update disconnectedCallback so a "hiding" element
transitions to "showing" rather than "idle", while retaining the existing
"pending" reset. Preserve the showing state and output attributes during
reparenting so connectedCallback and `#evaluate` reuse the original `#shownAt`
without firing `#show` or bones:show again.
- Around line 244-248: Update the transition flow around `#canTransition`() to
attach rejection handlers for ready, updateCallbackDone, and finished on the
ViewTransition returned by document.startViewTransition(update), including
AbortError from superseded transitions and update callback failures. Update the
test stubs to expose these promises and add regression coverage for a superseded
transition without unhandled rejections.
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.changeset/bones-boundary-element.mdREADME.mdapps/docs/content/docs/api/bones-boundary.mdxapps/docs/content/docs/api/meta.jsonpackages/bones/README.mdpackages/bones/package.jsonpackages/bones/sandbox/boundary.htmlpackages/bones/src/element/boundary.tspackages/bones/src/element/index.tspackages/bones/src/react/boundary.tspackages/bones/src/react/index.tspackages/bones/tests/boundary-react.test.tsxpackages/bones/tests/boundary.test.tspackages/bones/vite.config.ts
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bones.css picks --bone-base from prefers-color-scheme, so a page that keeps a white canvas in dark mode paints dark-mode bones white on white. Declare color-scheme: light dark on the sandbox so the canvas follows the scheme. Library-level follow-up tracked as BON-13. Co-Authored-By: Claude Fable 5 <[email protected]>
…ejections Review feedback from CodeRabbit on #34: - disconnectedCallback rolls a hiding element back to showing instead of idle. A moved element then re-evaluates from its original shownAt and hides on schedule instead of re-adopting and firing a second bones:show; a removed element still fires nothing. Each hide also carries a token so a callback from a superseded hide does nothing. - Attach no-op rejection handlers to the ViewTransition's ready, updateCallbackDone, and finished promises. A superseded transition rejects ready with AbortError, which is the normal case when two boundaries hide in the same frame. - Docs: the wrapper does render aria-busy and inert when force is true, so say that React owns those two in that case and the element writes them back while bones are showing. Co-Authored-By: Claude Fable 5 <[email protected]>
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Phase 2 of the roadmap, PR 1 of 2 for BON-3. Adds
@camp.dev/bones/element, a<bones-boundary>custom element that owns the loading state of its subtree, and a<BonesBoundary>wrapper in@camp.dev/bones/react. PR 2 (visual-regression tests in Vitest browser mode) follows separately.What the element does
Set
busyon the element and it setsaria-busy="true"andinerton itself afterdelay(200 ms), keeps them for at leastmin-duration(400 ms), then removes them insidedocument.startViewTransition()when the browser has it and the user has not asked for reduced motion. It firesbones:showandbones:hide, honorsforcefor demos, and adopts server-renderedaria-busy="true"on upgrade. It draws nothing:bones.cssandauto.cssalready key onaria-busy="true".Three places this departs from the BON-3 issue text
busyis the input;aria-busyis the output. The issue said the element observes its ownaria-busy.auto.csspaints the moment that attribute lands, so there would be nothing left fordelayto delay. Splitting intent from rendered state is what makes the timing attributes possible.<bones-boundary busy aria-busy="true" inert>), and the element adopts it on upgrade.inertgoes on the host, not per child. It survives children being swapped while busy, which is what htmx swaps and Phase 4 streaming do.React wrapper
<BonesBoundary>uses no hooks, so it renders inside server components. It mapsminDurationto themin-durationattribute for server output, emitsaria-busy/inertonly forforce, and passesonShow/onHideas the propsonbones:show/onbones:hide, which React 19 binds as listeners on custom elements. Apps import@camp.dev/bones/elementonce in a client entry; the React entry never touchescustomElements.The whole-branch review found that React owns
aria-busyandinerton the client after the wrapper renders them forforce, and strips them on the next render. The element now defends its own outputs while showing or draining, and has a fifthhidingstate so abusythat arrives while a view transition's update callback is still queued does not end up withshowing === trueand no bones. The wrapper also setssuppressHydrationWarning, since the element may have painted before React hydrates.Verification
vp run --filter @camp.dev/bones checkvp run --filter @camp.dev/bones test -- --runvp run --filter @camp.dev/bones builddist/element/presentvp run --filter bones-demo check/test -- --run/buildvp run --filter bones-docs check/build/api/bones-boundaryemittednode -e "await import('./dist/element/index.mjs')"HTMLElement)One local quirk, pre-existing on
main:vp checkinpackages/bonesreports formatting issues for the gitignoreddist/output when it exists. CI runs the check before the build, so it is unaffected. Deletedist/before running the check locally.Sandbox validation
packages/bones/sandbox/boundary.html, driven in headless Chromium 1217 (playwright-corewith the cached binary), 13 checks:busy; bones,inert, and onebones:showafter the delay;auto.csspaints the text barsbusyclears, thenbones:hideinside exactly onestartViewTransitioncallbusyon and off within the delay: no bones, no eventsdelay="0"shows synchronouslytransition="none"hides withoutstartViewTransitionforceshows at once, stays, and hides when clearedbone-pulseanimation instead of shimmerNot run: Firefox (not installed here). The fallback path it would exercise (no
startViewTransition) is the same one jsdom runs in the unit tests.Not in this PR
Visual-regression tests (PR 2), a fallback slot for streamed content (Phase 4), measured bones (BON-4), the BON-11 nested-flag fix, and the demo app, whose loading states come from
<Bones>and Suspense.Summary by CodeRabbit
New Features
<bones-boundary>custom element for delayed loading states, accessibility support, minimum display duration, and optional view transitions.<BonesBoundary>wrapper with event callbacks and hydration support.Documentation
Tests