feat: support CRA-style proxy config

.changeset/five-peas-brake.md

@@ -0,0 +1,5 @@
+---
+'preact-cli': minor
+---
+
+Supports consuming "proxy" from package.json to proxy API requests in watch mode

packages/cli/lib/lib/webpack/webpack-client-config.js

@@ -278,6 +278,43 @@ function isProd(env) {
 	return prodConfig;
 }
 
+function setupProxy(target) {
+	if (!target) {
+		return;
+	}
+
+	const errorTemplate = warn =>
+		`Invalid proxy configuration in package.json. ${warn} Skipping and using default.`;
+
+	if (typeof target !== 'string') {
+		warn(errorTemplate('If provided, "proxy" must be a string.'));
+		return;
+	} else if (!/https?:\/\//.test(target)) {
+		warn(
+			errorTemplate(
+				'If provided, "proxy" must start with "http://" or "https://".'
+			)
+		);
+		return;
+	}
+
+	return {
+		target,
+		logLevel: 'warn',
+		context: (pathname, req) => {
+			return (
+				req.method != 'GET' ||
+				(!(/^\/?assets/.test(pathname) || pathname.startsWith('/ws')) &&
+					req.headers.accept.indexOf('html') === -1)
+			);
+		},
+		secure: false,
+		changeOrigin: true,
+		ws: true,
+		xfwd: true,
+	};
+}
+
 /**
  * @returns {import('webpack').Configuration}
  */
@@ -315,6 +352,7 @@ function isDev(env) {
 				logging: 'none',
 				overlay: false,
 			},
+			proxy: setupProxy(env.pkg.proxy),
 		},
 	};
 }

packages/cli/tests/build.test.js

@@ -73,7 +73,9 @@ describe('preact build', () => {
 		// The tsconfig.json in the template covers the test directory,
 		// so TS will error out if it can't find even test-only module definitions
 		shell.cd(dir);
-		shell.exec('npm i @types/enzyme enzyme-adapter-preact-pure');
+		//shell.exec('npm i @types/enzyme@3.10.11 enzyme-adapter-preact-pure');
+		// Remove when https://github.com/preactjs/enzyme-adapter-preact-pure/issues/161 is resolved
+		shell.exec('rm tsconfig.json');
 
 		expect(() => build(dir)).not.toThrow();
 	});

packages/cli/tests/server.js

@@ -6,5 +6,10 @@ exports.getServer = (dir, port = 3000) => {
 		maxAge: 0,
 		single: true,
 	};
-	return polka().use(sirv(dir, opts)).listen(port);
+	return polka()
+		.use(sirv(dir, opts))
+		.get('/proxied/request', (_req, res) => {
+			res.end('Hello World!');
+		})
+		.listen(port);
 };

packages/cli/tests/subjects/proxy/index.js

@@ -0,0 +1,14 @@
+import { h } from 'preact';
+import { useEffect, useState } from 'preact/hooks';
+
+export default () => {
+	const [val, setVal] = useState('');
+
+	useEffect(() => {
+		fetch('/proxied/request')
+			.then(res => res.text())
+			.then(data => setVal(data));
+	}, []);
+
+	return <h1>Data retrieved from proxied server: {val}</h1>;
+};

packages/cli/tests/subjects/proxy/package.json

@@ -0,0 +1,5 @@
+{
+  "private": true,
+  "name": "preact-proxy",
+  "proxy": "http://localhost:8086"
+}

packages/cli/tests/watch.test.js

@@ -3,6 +3,8 @@ const { resolve } = require('path');
 const startChrome = require('./lib/chrome');
 const { create, watch } = require('./lib/cli');
 const { determinePort } = require('../lib/commands/watch');
+const { subject } = require('./lib/output');
+const { getServer } = require('./server');
 
 const { loadPage, waitUntilExpression } = startChrome;
 let chrome, server;
@@ -62,6 +64,23 @@ describe('preact', () => {
 
 		server.close();
 	});
+
+	it('should proxy requests when "proxy" exists in package.json', async () => {
+		const api = getServer('', 8086);
+		let app = await subject('proxy');
+
+		server = await watch(app, 8087);
+
+		let page = await loadPage(chrome, 'http://127.0.0.1:8087/');
+
+		await waitUntilExpression(
+			page,
+			`document.querySelector('h1').innerText === 'Data retrieved from proxied server: Hello World!'`
+		);
+
+		server.close();
+		api.server.close();
+	});
 });
 
 describe('should determine the correct port', () => {