<div align="center">
# LiveSvelte
Svelte inside Phoenix LiveView with seamless end-to-end reactivity
[Features](#features) •
[Resources](#resources) •
[Demo](#demo) •
[Installation](#installation) •
[Usage](#usage)
</div>
## Features
- ⚡ **End-To-End Reactivity** with LiveView
- 🔋 **Server-Side Rendered** (SSR) Svelte
- 🪄 **Sigil** as an [Alternative LiveView DSL](#livesvelte-as-an-alternative-liveview-dsl)
- ⭐ **Svelte Preprocessing** Support with [svelte-preprocess](https://github.com/sveltejs/svelte-preprocess)
- 🦄 **Tailwind** Support
- 💀 **Dead View** Support
- 🦥 **Slot Interoperability** _(Experimental)_
## Resources
- [HexDocs](https://hexdocs.pm/live_svelte)
- [HexPackage](https://hex.pm/packages/live_svelte)
- [Phoenix LiveView](https://github.com/phoenixframework/phoenix_live_view)
- [Blog Post](https://wout.space/notes/live-svelte)
- [YouTube Introduction](https://www.youtube.com/watch?v=JMkvbW35QvA)
## Demo
For a full intro and demo check out the [YouTube introduction](https://www.youtube.com/watch?v=JMkvbW35QvA)
`/examples/advanced_chat`
https://user-images.githubusercontent.com/3637265/229902870-29166253-3d18-4b24-bbca-83c4b6648578.webm
<br />
Svelte handles the look and feel of the chat, while LiveView takes care of syncing. E2E reactivity to the Svelte component so we don't really need to fetch anything! The 'login' to enter your name is a simple LiveView form. Hybrid!
---
`/examples/breaking_news`
https://user-images.githubusercontent.com/3637265/229902860-f7ada6b4-4a20-4105-9ee9-79c0cbad8d72.webm
<br />
News items are synced with the server while the speed is only client side.
## Why LiveSvelte
Phoenix LiveView enables rich, real-time user experiences with server-rendered HTML.
It works by communicating any state changes through a websocket and updating the DOM in realtime.
You can get a really good user experience without ever needing to write any client side code.
LiveSvelte builds on top of Phoenix LiveView to allow for easy client side state management while still allowing for communication over the websocket.
### Reasons why you'd use LiveSvelte
- You have (complex) local state
- You want to take full advantage of Javascript's ecosystem
- You want to take advantage of Svelte's animations
- You want scoped CSS
- You like Svelte and its DX :)
## Requirements
For Server-Side Rendering (SSR) to work you need `node` (version 19 or later) installed in your environment.
Make sure you have it installed in production too. You might be using `node` only in the build step, but it might actually not be installed in your production environment.
You can make sure you have `node` installed by running `node --version` in your project directory.
If you don't want SSR, you can disable it by not setting `NodeJS.Supervisor` in `application.ex`. More on that in the [SSR](#ssr-server-side-rendering) section of this document.
## Installation
1. Add `live_svelte` to your list of dependencies in `mix.exs`:
```elixir
defp deps do
[
{:live_svelte, "~> 0.4.2"}
]
end
```
2. Adjust the `setup` and `assets.deploy` aliases in `mix.exs`:
```elixir
defp aliases do
[
setup: ["deps.get", "ecto.setup", "cmd --cd assets npm install"],
...,
"assets.deploy": ["cmd --cd assets node build.js --deploy", "phx.digest"]
]
end
```
3. Run the following in your terminal
```bash
mix deps.get
mix live_svelte.setup
```
4. For tailwind support, add `"./svelte/**/*.svelte"` to `content` in the `tailwind.config.js` file
```javascript
...
content: [
...
"./svelte/**/*.svelte"
],
...
```
5. Finally, remove the `esbuild` configuration from `config/config.exs` and remove the dependency from the `deps` function in your `mix.exs`, and you are done!
### What did we do?
You'll notice a bunch of files get created in `/assets`, as well as some code changes in `/lib`. This mostly follows from the recommended way of using esbuild plugins, which we need to make this work. You can read more about this here: <https://hexdocs.pm/phoenix/asset_management.html#esbuild-plugins>
In addition we commented out some things such as the `esbuild` watcher configured in `dev.exs` that won't be needed anymore, you can delete these comments if desired.
## Usage
Svelte components need to go into the `assets/svelte` directory
Attributes:
- `name`: Specify the Svelte component
- `props` _(Optional)_: Provide the `props` you want to use that should be reactive as a map to the props field
- `class` _(Optional)_: Provide `class` to set the class attribute on the root svelte element
- `ssr` _(Optional)_: Set `ssr` to `false` to disable server-side rendering
e.g. If your component is named `assets/svelte/Example.svelte`:
```elixir
def render(assigns) do
~H"""
<LiveSvelte.render name="Example" props={%{number: @number}} />
"""
end
```
If your component is in a directory, for example `assets/svelte/some-directory/SomeComponent.svelte` you need to include the directory in your name: `some-directory/SomeComponent`.
### Examples
Examples can be found in the `/examples` and `/example_project` directories.
Most of the `/example_project` examples are visible in the [YouTube demo video](https://www.youtube.com/watch?v=JMkvbW35QvA).
I recommend cloning `live_svelte` and running the example project in `/example_project` by running the following commands:
```
git clone https://github.com/woutdp/live_svelte.git
cd ./live_svelte/example_project
npm install --prefix assets
mix deps.get
mix phx.server
```
Server should be running on `localhost:4000`
If you have examples you want to add, feel free to create a PR, I'd be happy to add them.
#### Create a Svelte component
```svelte
<script>
// The number prop is reactive,
// this means if the server assigns the number, it will update in the frontend
export let number = 1
// pushEvent to ... push events to the server.
export let pushEvent
function increase() {
// This pushes the event over the websocket
// The last parameter is optional. It's a callback for when the event is finished.
// You could for example set a loading state until the event is finished if it takes a longer time.
pushEvent("set_number", {number: number + 1}, () => {})
// Note that we actually never set the number in the frontend!
// We ONLY push the event to the server.
// This is the E2E reactivity in action!
// The number will automatically be updated through the LiveView websocket
}
function decrease() {
pushEvent("set_number", {number: number - 1}, () => {})
}
</script>
<p>The number is {number}</p>
<button on:click={increase}>+</button>
<button on:click={decrease}>-</button>
```
_Note that here we use the pushEvent function, but you could also use `phx-click` and `phx-value-number` if you wanted._
#### Create a LiveView
```elixir
# `/lib/app_web/live/live_svelte.ex`
defmodule AppWeb.SvelteLive do
use AppWeb, :live_view
def render(assigns) do
~H"""
<LiveSvelte.render name="Example" props={%{number: @number}} />
"""
end
def handle_event("set_number", %{"number" => number}, socket) do
{:noreply, assign(socket, :number, number)}
end
def mount(_params, _session, socket) do
{:ok, assign(socket, :number, 5)}
end
end
```
```elixir
# `/lib/app_web/router.ex`
import Phoenix.LiveView.Router
scope "/", AppWeb do
...
live "/svelte", SvelteLive
...
end
```
### LiveSvelte As An Alternative LiveView DSL
We can go one step further and use LiveSvelte as an alternative to the standard LiveView DSL. This idea is inspired by [Surface UI](https://surface-ui.org/).
Take a look at the following example:
```elixir
defmodule ExampleWeb.LiveSigil do
use ExampleWeb, :live_view
def render(assigns) do
~V"""
<script>
export let number = 5
let other = 1
$: combined = other + number
</script>
<p>This is number: {number}</p>
<p>This is other: {other}</p>
<p>This is other + number: {combined}</p>
<button phx-click="increment">Increment</button>
<button on:click={() => other += 1}>Increment</button>
"""
end
def mount(_params, _session, socket) do
{:ok, assign(socket, :number, 1)}
end
def handle_event("increment", _value, socket) do
{:noreply, assign(socket, :number, socket.assigns.number + 1)}
end
end
```
Use the `~V` sigil instead of `~H` and your LiveView will be Svelte instead of an HEEx template.
#### Installation
1. Add `import LiveSvelte` inside the `live_view` function in your project, this can be found in `/lib/<app_name>_web.ex`:
```elixir
def live_view do
quote do
use Phoenix.LiveView,
layout: {ExampleWeb.Layouts, :app}
import LiveSvelte
unquote(html_helpers())
end
end
```
2. Ignore build files in your `.gitignore`. The sigil will create Svelte files that are then picked up by `esbuild`, these files don't need to be included in your git repo:
```gitignore
# Ignore automatically generated Svelte files by the ~V sigil
/assets/svelte/_build/
```
#### Neovim Treesitter Config
To enable syntax highlighting in Neovim with Treesitter, create the following file:
`~/.config/nvim/after/queries/elixir/injections.scm`
```
; extends
; Svelte
(sigil
(sigil_name) @_sigil_name
(quoted_content) @svelte
(#eq? @_sigil_name "V"))
```
Also make sure Svelte and Elixir is installed in Treesitter.
#### Options
Options can be passed in the mount by setting `svelte_opts`, check the following example:
```elixir
def mount(_params, _session, socket) do
{:ok, assign(socket, some_value: 1, svelte_opts: %{ssr: false, class: "example-class"})}
end
```
### LiveView Live Navigation Events
Inside Svelte you can define [Live Navigation](https://hexdocs.pm/phoenix_live_view/live-navigation.html) links. These links navigate from one LiveView to the other without refreshing the page.
For example this can be useful when you have a Svelte store and you want this store state to remain during navigation. Example of Svelte store usage can be found in `/examples/store`.
`push_navigate`
```svelte
<a href="/your-liveview-path" data-phx-link="redirect" data-phx-link-state="push">Redirect</a>
```
`push_patch`
```svelte
<a href="/your-liveview-path" data-phx-link="patch" data-phx-link-state="push">Patch</a>
```
### LiveView JavaScript Interoperability
LiveView allows for a bunch of interoperability which you can read more about here:
<https://hexdocs.pm/phoenix_live_view/js-interop.html>
### Preprocessor
To use the preprocessor, install the desired preprocessor.
e.g. Typescript
```
cd assets && npm install --save-dev typescript
```
### SSR (Server-Side Rendering)
If you're unfamiliar with SSR (Server-Side Rendering), it is a feature of Svelte to... render Svelte on the server. This means on first page load you get to see HTML instead of a blank page. Immediately after the first page load the page is '[hydrated](https://www.youtube.com/watch?v=D46aT3mx9LU)', which is a fancy word for adding reactivity to your component. This happens in the background, you don't notice this step happening.
The way LiveSvelte updates itself through LiveView is by letting Svelte handle all the HTML edits. Usually LiveView would edit the HTML by passing messages through the websocket. In our case we only pass the data we provided in the props attribute to Svelte through the websocket. No HTML is being touched by LiveView, Svelte takes care of that.
Like mentioned, without SSR you'd see a brief flash of un-rendered content. Sometimes you can get away with not rendering Svelte on the server, for example when your Svelte component doesn't do any rendering on first page load and needs to be manually toggled for visibility by the user. Or when it is a component that has no visual component to it like tracking your mouse cursor and sending it back to the server.
In theses cases you can turn of SSR.
#### Disabling SSR
SSR is enabled by default when you install LiveSvelte. If you don't want to use Server-Side Rendering for Svelte, you have 2 options:
##### Globally
If you don't want to use SSR on any component you can disable it globally.
This will automatically be the case if you don't include the `NodeJS` supervisor in the `application.ex` file
##### Component
To disable SSR on a specific component, set the `ssr` property to false. Like so:
```
<LiveSvelte.render name="Example" ssr={false} />
```
### Structs and Ecto
We use [Jason](https://github.com/michalmuskala/jason) to serialize any data you pass in the props so it can be handled by Javascript.
Jason doesn't know how to handle structs by default, so you need to define it yourself.
#### Structs
For example, if you have a regular struct like this:
```elixir
defmodule User do
defstruct name: "John", age: 27, address: "Main St"
end
```
You must define `@derive`
```elixir
defmodule User do
@derive Jason.Encoder
defstruct name: "John", age: 27, address: "Main St"
end
```
Be careful though, as you might accidentally leak certain fields you don't want the client to access, you can include which fields to serialize:
```elixir
defmodule User do
@derive {Jason.Encoder, only: [:name, :age]}
defstruct name: "John", age: 27, address: "Main St"
end
```
#### Ecto
In ecto's case it's important to _also_ emit the `__meta__` field as it's not serializable.
Check out the following example:
```elixir
defmodule Example.Planets.Planet do
use Ecto.Schema
import Ecto.Changeset
@derive {Jason.Encoder, except: [:__meta__]}
schema "planets" do
field :diameter, :integer
field :mass, :integer
field :name, :string
timestamps()
end
...
end
```
#### Documentation
More documentation on the topic:
- [HexDocs](https://hexdocs.pm/jason/Jason.Encoder.html)
- [GitHub](https://github.com/michalmuskala/jason#encoders)
## Caveats
### Slot Interoperability
Slot interoperability is still experimental, **so use with caution!**
Svelte doesn't have an official way of setting the slot on mounting the Svelte object or updating it on subsequent changes, unlike props. This makes using slots from within Liveview on a Svelte component fragile.
The server side rendered initial Svelte rendering does have support for slots so that should work as expected.
Slots may eventually reach a state where it is stable, any help in getting there is appreciated. If you know a lot about the internals of Svelte your help may be invaluable here!
Any bugs related to this are welcome to be logged, PR's are especially welcome!
## Development
### Building Static Files
Make the changes in `/assets/js` and run:
```bash
mix assets.build
```
Or run the watcher:
```bash
mix assets.build --watch
```
### Local Setup
#### Example Project
You can use `/example_project` as a way to test `live_svelte` locally.
#### Custom Project
You can also use your own project.
Clone `live_svelte` to the parent directory of the project you want to test it in.
Inside `mix.exs`
```elixir
{:live_svelte, path: "../live_svelte"},
```
Inside `assets/package.json`
```javascript
"live_svelte": "file:../../live_svelte",
```
### Releasing
- Update the version in `README.md`
- Update the version in `package.json`
- Update the version in `mix.exs`
- Update the changelog
Run:
```bash
mix hex.publish
```
## Credits
- [Ryan Cooke](https://dev.to/debussyman) - [E2E Reactivity using Svelte with Phoenix LiveView](https://dev.to/debussyman/e2e-reactivity-using-svelte-with-phoenix-liveview-38mf)
- [Svonix](https://github.com/nikokozak/svonix)
- [Sveltex](https://github.com/virkillz/sveltex)
## LiveSvelte Projects
- [ash-svelte-flowbite](https://github.com/dev-guy/ash-svelte-flowbite)
_Using LiveSvelte in a public project? Let me know and I'll add it to this list!_
