Add WebAssembly example

examples/with-webassembly/.gitignore

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+.next

examples/with-webassembly/Cargo.toml

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+[package]
+name = "next-rust"
+version = "0.1.0"
+authors = ["Tim Neutkens <timneutkens@me.com>"]
+
+[dependencies]

examples/with-webassembly/next.config.js

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+module.exports = {
+  webpack (config) {
+    config.output.webassemblyModuleFilename = 'static/wasm/[modulehash].wasm'
+    return config
+  }
+}

examples/with-webassembly/package.json

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+{
+  "dependencies": {
+    "next": "canary",
+    "react": "^16.4.2",
+    "react-dom": "^16.4.2"
+  },
+  "scripts": {
+    "dev": "node server.js",
+    "build": "next build",
+    "build-rust": "rustc +nightly --target wasm32-unknown-unknown -O --crate-type=cdylib src/add.rs -o add.wasm",
+    "start": "NODE_ENV=production node server.js"
+  }
+}

examples/with-webassembly/pages/index.js

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+import {withRouter} from 'next/router'
+import dynamic from 'next/dynamic'
+import Link from 'next/link'
+
+const RustComponent = dynamic({
+  loader: async () => {
+    // Import the wasm module
+    const rustModule = await import('../add.wasm')
+    // Return a React component that calls the add_one method on the wasm module
+    return (props) => <div>
+      {rustModule.add_one(props.number)}
+    </div>
+  }
+})
+
+const Page = ({router: {query}}) => {
+  const number = parseInt(query.number || 30)
+  return <div>
+    <RustComponent number={number} />
+    <Link href={`/?number=${number + 1}`}><a>+</a></Link>
+  </div>
+}
+
+export default withRouter(Page)

examples/with-webassembly/readme.md

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+[![Deploy to now](https://deploy.now.sh/static/button.svg)](https://deploy.now.sh/?repo=https://github.com/zeit/next.js/tree/master/examples/hello-world)
+
+# WebAssembly example
+
+## How to use
+
+### Using `create-next-app`
+
+Execute [`create-next-app`](https://github.com/segmentio/create-next-app) with [Yarn](https://yarnpkg.com/lang/en/docs/cli/create/) or [npx](https://github.com/zkat/npx#readme) to bootstrap the example:
+
+```bash
+npx create-next-app --example with-webassembly with-webassembly-app
+# or
+yarn create next-app --example with-webassembly with-webassembly-app
+```
+
+### Download manually
+
+Download the example:
+
+```bash
+curl https://codeload.github.com/zeit/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/with-webassembly
+cd with-webassembly
+```
+
+Install it and run:
+
+This example uses Rust compiled to wasm, the wasm file is included in the example, but to compile your own Rust code you'll have to [install](https://www.rust-lang.org/en-US/) Rust.
+
+```bash
+npm install
+npm run dev
+# or
+yarn
+yarn dev
+```
+
+To compile `src/add.rs` to `add.wasm` use `npm run build-rust`.
+
+Deploy it to the cloud with [now](https://zeit.co/now) ([download](https://zeit.co/download))
+
+```bash
+now
+```
+
+## The idea behind the example
+
+This example shows how to import WebAssembly files (`.wasm`) and use them inside of a React component that is server rendered. So the WebAssembly code is executed on the server too. In the case of this example we're showing Rust compiled to WebAssembly.

examples/with-webassembly/server.js

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+const { createServer } = require('http')
+const { parse } = require('url')
+const next = require('next')
+
+const dev = process.env.NODE_ENV !== 'production'
+const app = next({ dev })
+const handle = app.getRequestHandler()
+
+app.prepare().then(() => {
+  createServer((req, res) => {
+    // Be sure to pass `true` as the second argument to `url.parse`.
+    // This tells it to parse the query portion of the URL.
+    const parsedUrl = parse(req.url, true)
+
+    // Set Content-Type to application/wasm for wasm files
+    if (parsedUrl.pathname.includes('/_next/static/wasm')) {
+      res.setHeader('Content-Type', 'application/wasm')
+    }
+
+    handle(req, res, parsedUrl)
+  }).listen(3000, err => {
+    if (err) throw err
+    console.log('> Ready on http://localhost:3000')
+  })
+})

examples/with-webassembly/src/add.rs

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+#[no_mangle]
+pub extern "C" fn add_one(x: i32) -> i32 {
+    x + 1
+}