# AssetImport
Webpack asset imports directly in Elixir code. For example in Phoenix controllers/views/templates or LiveView's.
## Features
- Only load assets that are used for current render.
- Helps to avoid assets over, under, or double fetching.
- Optimal asset packaging and cache reuse with Webpack code splitting.
- Supports Phoenix LiveView's by loading assets dynamically.
- Supports mix dependencies that are using `asset_import`.
## Installation
The package can be installed by adding `asset_import` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:asset_import, "~> 0.4.6"}
]
end
```
## Usage
```css
/* assets/css/forms.css */
form {
/* a lot of form styling, or import bootstrap `_forms.scss` etc */
}
```
```javascript
// assets/js/login_form.js
import "../css/forms.css"
// some login form specific javascript here
```
Anywhere in your views, templates, or LiveView renders:
```html
<div>
<%= if @logged_in do %>
<div>My profile..</div>
<% else %>
<!--
You can use <% asset_import @conn, "js/login_form" %> (without =),
if you are not using this template in LiveView. It will save some bytes from your html.
-->
<%= asset_import @conn, "js/login_form" %>
<!--
Inside LiveView use @socket instead @conn
-->
<%= asset_import @socket, "js/login_form" %>
<form>Login form..</form>
<% end %>
</div>
```
Assets `js/login_form.js` and `css/forms.css` are only loaded when user is not logged in.
## Setup
### 1. Configuration
Typical `asset_import` config:
```elixir
# config/config.exs
config :asset_import, MyAppWeb.Assets,
assets_base_url: "/",
assets_path: Path.expand("assets"),
manifest_path: Path.expand("priv/static/manifest.json"),
entrypoints_path: Path.expand("assets/entrypoints.json")
```
Replace phoenix watcher from `webpack` to `nodemon`:
```elixir
# config/dev.exs
config :my_app, MyAppWeb.Endpoint,
debug_errors: true,
code_reloader: true,
check_origin: false,
watchers: [node: ["node_modules/nodemon/bin/nodemon.js", cd: Path.expand("../assets", __DIR__)]]
```
Disable entrypoints file generation in test.
```elixir
# config/test.exs
config :asset_import, entrypoints_path: :disabled
```
### 2. Create an assets module
```elixir
defmodule MyAppWeb.Assets do
use AssetImport,
assets_path: "assets" # optional, defaults to "assets"
use AwesomeUiComponents.Assets # add dependency assets
end
```
### 3. Use your assets module in web module
```elixir
defmodule MyAppWeb do
..
def view do
quote do
..
use MyAppWeb.Assets
..
end
end
..
end
```
### 4. Import file macros to your layout view
```elixir
defmodule MyAppWeb.LayoutView do
use MyAppWeb, :view
import MyAppWeb.Assets.Files
end
```
### 5. Add scripts and styles to layout
```html
<!-- Content rendering has to execute before scripts and styles -->
<% body = render "body.html", assigns %>
<html>
<head>
<!-- Styles for current page (render blocking) -->
<%= asset_styles() %>
<!-- Optional: Preload unused styles and scripts -->
<%= preload_asset_styles() %>
<%= preload_asset_scripts() %>
</head>
<body>
<%= body %>
<!-- Scripts for current page -->
<%= asset_scripts() %>
</body>
</html>
```
Or
```html
<!-- Content rendering has to execute before scripts and styles -->
<% body = render "body.html", assigns %>
<html>
<head>
<!-- Styles for current page (render blocking) -->
<%= for path <- asset_style_files() do %>
<link rel="stylesheet" href="<%= path %>" />
<% end %>
<!-- Optional: Preload unused styles and scripts -->
<%= for path <- unused_asset_style_files() do %>
<link rel="preload" href="<%= path %>" as="style">
<% end %>
<%= for path <- unused_asset_script_files() do %>
<link rel="preload" href="<%= path %>" as="script">
<% end %>
</head>
<body>
<%= body %>
<!-- Scripts for current page -->
<%= for path <- asset_script_files() do %>
<script type="text/javascript" src="<%= path %>"></script>
<% end %>
</body>
</html>
```
### 6. Add LiveView hook (only when LiveView is used)
```javascript
import LiveSocket from "phoenix_live_view"
import Socket from "phoenix"
import AssetImport from "asset_import_hook"
let liveSocket = new LiveSocket("/live", Socket, { AssetImport })
liveSocket.connect()
```
### 7. Webpack setup
Copy `example_assets/*` to your project assets or adjust existing files manually:
- ```javascript
// assets/nodemon.json
{
"watch": ["entrypoints.json", "webpack.config.js"],
"exec": "node_modules/webpack/bin/webpack.js --color --mode development --watch-stdin"
}
```
- ```javascript
// assets/package.json
{
..
"dependencies": {
..
"asset_import_hook": "0.4.6" // only when LiveView is used
..
},
"devDependencies": {
..
"nodemon": "1.19.2",
"uglifyjs-webpack-plugin": "2.2.0",
..
}
}
```
- ```javascript
// assets/webpack.config.js
..
8: const entrypoints = require('./entrypoints.json') || {};
9:
10: if (Object.keys(entrypoints).length === 0) {
11: console.log('No entrypoints');
12: process.exit();
13: return;
14: }
..
23: runtimeChunk: 'single',
24: chunkIds: 'natural',
25: concatenateModules: true,
26: splitChunks: {
27: chunks: 'all',
28: minChunks: 1,
29: minSize: 0
30: }
31: },
32: entry: entrypoints,
33: output: {
34: filename: 'js/[id]-[contenthash].js',
35: chunkFilename: 'js/[id]-[contenthash].js',
36: path: path.resolve(__dirname, '../priv/static')
37: },
38: plugins: [
39: new MiniCssExtractPlugin({
40: filename: 'css/[id]-[contenthash].css',
41: chunkFilename: 'css/[id]-[contenthash].css',
42: }),
43: new ManifestPlugin({ fileName: 'manifest.json' }),
..
```
