keen_phoenix_svelte

# keen_phoenix_svelte


**🌐 Live demo & docs: [keen-phoenix-svelte.keenmate.dev](https://keen-phoenix-svelte.keenmate.dev)** ·
[Hex](https://hex.pm/packages/keen_phoenix_svelte) ·
[HexDocs](https://hexdocs.pm/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:

```heex

<.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 (plus a `bus` for island-to-island messaging), and torn down on
navigation — no manual `<script>`/`<link>` wiring. A configurable placeholder
shows while the bundle loads (server-wide default, per-app `<:placeholder>`
override), so there's no flash of empty container.

Svelte is the first-class, tooled path, but the mount boundary is
**framework-neutral** — an island's entry just default-exports
`(target, opts) => { setProps, destroy }`. Because every island mounts through
that one contract, there's a single component, `<.app>` (an optional
`framework="…"` attribute just tags `data-framework` for debugging). The demo
mounts Svelte, Lit, React and vanilla-JS islands through it. `<.svelte>` remains
as a back-compat alias.

> **New here, or comparing this to `live_svelte`?** Start with

> **[Philosophy & comparison](docs/philosophy.md)** — 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.3


- **Proxy cache with revalidation — `:proxy` mode now works for unversioned upstreams** — Registered proxied bundles are cached in ETS and *revalidated* rather than pinned forever: a stale entry triggers a single-flight conditional `GET` (`If-None-Match`/`If-Modified-Since`), so a `304` keeps the bytes and a `200` swaps them, with concurrent requests collapsed into one upstream fetch. Freshness follows the upstream's `Cache-Control`/`ETag`, falling back to a `:ttl` (default 5 min) — so a bare `cdn/app.js` with no version in its URL is re-checked on a cadence instead of cached for a year.
- **End-to-end conditional-request chain** — The proxy forwards an `ETag` (synthesizing a weak one when the origin ships none) and answers the browser's `If-None-Match` with a `304`, so browser → Phoenix → origin all revalidate cheaply. This replaces the old fixed 1-year `immutable` header; a per-app `immutable: true` opts truly-versioned URLs back into it.
- **Bounded proxy memory** — Cache entries upsert by URL (refreshes never grow the table) and a periodic sweep evicts URLs no longer in the registry, so a rotating DB-driven app registry stays bounded to its working set.
- **Renamed to speak "app", not "island"** — `KeenPhoenixSvelte.IslandProxy` → `KeenPhoenixSvelte.Apps.Proxy`, config `:island_provider` → `:app_provider` (which now also accepts a 2-arity conditional-fetch form), and the proxy-path default `/keen-islands` → `/apps` (it shares the `base_path` prefix). Update your router `forward`.
- **Package metadata / links** — corrected the `:source_url` casing, added `homepage_url`, and a `Website` link to the live demo.

## What's New in v1.0.0-rc.2


- **Framework-neutral `<.app>` — one component mounts any island** — Every island mounts through the same `(target, opts) => { setProps, destroy }` contract, so there is now a single `app/1` component regardless of whether the bundle is Svelte, Lit, React, or hand-written vanilla JS. An optional `framework` attribute just emits an informational `data-framework` tag. `<.svelte>` remains as a back-compat alias for the rc.1 name.
- **Placeholder / loader — no flash of empty container** — `<.app>` renders a placeholder that the client clears the instant the bundle mounts (after the fetch, so it stays visible the whole time). Resolution is a per-call `<:placeholder>` slot › the server-wide `config :keen_phoenix_svelte, :placeholder` › a built-in, dependency-free skeleton. The server default accepts an HTML string, a function, `{mod, fun}`, or `false` to disable.
- **Event bus — island-to-island messaging without the server** — A `bus` joins the app boundary: a page-wide, client-side pub/sub (`emit`/`on`/`once`) over a DOM `EventTarget`, wired into both the LiveView hook and `mountStatic()`, so independent islands coordinate without a round-trip and without importing each other.
- **External apps — a registry with `:direct`/`:proxy` delivery** — `KeenPhoenixSvelte.Apps` registers islands whose bundle lives elsewhere (a CDN, another deploy); `<.runtime>` emits a `name → url` manifest and `AppsManager.resolve/1` loads them. Pick `:direct` (browser imports the CDN URL) or `:proxy` (Phoenix fetches and re-serves same-origin via `KeenPhoenixSvelte.Apps.Proxy` — no CORS, CSP `'self'`).
- **Example reworked into "KeenSpace"** — the demo is now a Teams-style workspace that doubles as reference code: chat over channel + Presence, a video catalogue over the REST helper, a calendar over `context.tokens`, a bus-driven activity toast, simulated i18n, a plain (non-LiveView) route, and Lit/React/vanilla islands alongside the Svelte ones.

## How it works


Two cooperating halves:

- **Elixir** — `<.app>` 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 island inside a LiveView and `AppsManager`
  lazily `import()`s `/apps/<name>/main.mjs` (or a registered URL); `mountStatic()`
  mounts islands on plain pages. Only the bundles on a page are fetched — and any
  framework's bundle mounts through the same `(target, opts) => { setProps, destroy }`
  contract.

`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


```elixir

{:keen_phoenix_svelte, "~> 1.0"}

```


Plus the npm package `@keenmate/phoenix_svelte` and a Svelte/Vite toolchain. Full
steps in [Installation & setup](docs/installation.md).

## Documentation


- [Installation & setup](docs/installation.md) — wire the library into your app
- [Authoring apps](docs/authoring-apps.md) — folder layout, the mount contract, Svelte 5 & 4
- [Server communication](docs/server-communication.md) — runtime context, `live`, `api`, `channel`, `bus`
- [External apps (CDN, direct vs proxy)](docs/external-apps.md) — load islands from elsewhere, and the `:direct`/`:proxy` delivery modes

A complete, runnable demo (the `like` app on a LiveView route and a plain route,
plus a channel) lives in the
[`example/`](https://github.com/KeenMate/keen-phoenix-svelte/tree/main/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.