keen_phoenix_svelte

Auto-mount compiled Svelte apps into Phoenix — on both LiveView and plain controller-rendered pages — as self-contained islands.

Write this in a template:

<.svelte name="like" id={"like-#{@id}"} props={%{id: @id, liked: @liked}} />

…and the compiled Svelte app in assets/apps/like/ is mounted into that element, kept in sync with server state, given a context/api/channel/live bridge to the server, and torn down on navigation — no manual <script>/<link> wiring.

New here, or comparing this to live_svelte? Start with Philosophy & comparison — the autonomous-island model, what this deliberately doesn't do, and how it differs from live_svelte.

What's New in v1.0.0-rc.1

• Islands for Phoenix — <.svelte> mounts compiled Svelte apps with zero per-page wiring — The initial release ships the core mounting path: a <.svelte name id props> function component renders a hook-bound <div> (phx-update="ignore", data-app, JSON data-props), and the KeenSvelte LiveView hook mounts the app on mounted(), pushes prop changes on updated(), and tears it down on destroyed(). AppsManager lazily import()s /apps/<name>/main.mjs and caches it, so only the bundles actually present on a page are fetched — no manual <script>/<link> tags per app.
• One component, two transports — LiveView socket or plain-page REST — Apps mount identically inside a LiveView or on a plain controller-rendered page. mountStatic() scans [data-app] on non-LiveView pages (skipping [data-phx-session]) and mounts with live: null, so the same app talks over live.pushEvent when a socket is present and falls back to the api REST helper when it isn't.
• A standardized app boundary — props, context, live, api, channel — Every app's entry receives (target, { props, context, live, api, channel, el }) => handle. context (emitted once per page by <KeenPhoenixSvelte.runtime>) carries user/csrf/tokens/api_base/socket; live bridges pushEvent/handleEvent (with automatic subscription cleanup)/upload; api attaches x-csrf-token + session cookie to REST calls; and channel is a promise-based, envelope-agnostic Phoenix channel factory with auto cid correlation.
• Svelte-version-agnostic mount contract — The mount handle is { setProps, destroy }, so the hook drives Svelte 5 (mount/unmount + $state) and transparently falls back to $set/$destroy on Svelte 4. Prop updates are diffed in updated() to skip redundant re-renders when data-props is unchanged.
• Dual package — Hex library + bundled npm package — Ships as both keen_phoenix_svelte on Hex and @keenmate/phoenix_svelte on npm, released in lockstep at the same version. A Vite config helper (@keenmate/phoenix_svelte/vite) builds one self-contained ES module per app with CSS injected by JS. A runnable Phoenix 1.8 demo (the like app on both a LiveView route and a plain route, plus a channel) lives in example/.

How it works

Two cooperating halves:

• Elixir — <.svelte> renders a hook-bound <div> (phx-update="ignore", data-app, JSON data-props); <KeenPhoenixSvelte.runtime> emits the page context.
• JS — the KeenSvelte hook mounts the app inside a LiveView and AppsManager lazily import()s /apps/<name>/main.mjs; mountStatic() mounts apps on plain pages. Only the bundles on a page are fetched.

phx-update="ignore" keeps LiveView out of the Svelte-owned subtree; the hook drives mount / prop-update / teardown across live navigation.

Unlike live_svelte, this is the island model — no ~V sigil, no server-rendered slots, no SSR Node runtime.

Install

{:keen_phoenix_svelte, "~> 1.0"}

Plus the npm package @keenmate/phoenix_svelte and a Svelte/Vite toolchain. Full steps in Installation & setup.

Documentation

• Installation & setup — wire the library into your app
• Authoring apps — folder layout, the mount contract, Svelte 5 & 4
• Server communication — runtime context, live, api, channel

A complete, runnable demo (the like app on a LiveView route and a plain route, plus a channel) lives in the example/ app.

Versioning

keen_phoenix_svelte is a dual package: the Hex library keen_phoenix_svelte and the npm package @keenmate/phoenix_svelte are released in lockstep at the same version — install matching versions of both. The Elixir side renders the component + hook wiring; the npm side supplies the client runtime (the KeenSvelte hook, AppsManager, the api/channel helpers, and the Vite build helper).

License

MIT.