implement --launcher

src/cli.ts

@@ -21,9 +21,18 @@ prog.command('dev')
 
 prog.command('build [dest]')
 	.describe('Create a production-ready version of your app')
-	.action(async (dest = 'build') => {
+	.option('-l, --launcher', 'Create a launcher file (defaults to start.js)')
+	.option('-p, --port', 'Default port, if using --launcher')
+	.example(`build -l`)
+	.example(`build custom-dir -l custom-launcher.js -p 4567`)
+	.action(async (dest = 'build', opts: { launcher: string | true, port: string }) => {
 		console.log(`> Building...`);
 
+		if (opts.port && !opts.launcher) {
+			console.error(`${clorox.bold.red(`You can only use the --port option with --launcher`)}`);
+			process.exit(1);
+		}
+
 		process.env.NODE_ENV = 'production';
 		process.env.SAPPER_DEST = dest;
 
@@ -32,7 +41,31 @@ prog.command('build [dest]')
 		try {
 			const { build } = await import('./cli/build');
 			await build();
-			console.error(`\n> Finished in ${elapsed(start)}. Type ${clorox.bold.cyan(dest === 'build' ? 'npx sapper start' : `npx sapper start ${dest}`)} to run the app.`);
+
+			let cmd;
+
+			if (opts.launcher) {
+				const launcher = opts.launcher === true ? 'start.js' : opts.launcher;
+				const resolvedLauncher = path.resolve(launcher);
+				const resolvedDest = path.resolve(dest);
+				const relative = path.relative(path.dirname(resolvedLauncher), resolvedDest);
+
+				fs.writeFileSync(resolvedLauncher, `
+					// generated by sapper build at ${new Date().toISOString()}
+					process.env.NODE_ENV = process.env.NODE_ENV || 'production';
+					process.env.SAPPER_DEST = require('path').resolve(__dirname, '${relative}');
+					process.env.PORT = process.env.PORT || ${opts.port || 3000};
+
+					console.log('Starting server on port ' + process.env.PORT);
+					require('${relative[0] === '.' ? relative : `./${relative}`}/server.js');
+				`.replace(/^\t+/gm, '').trim());
+
+				cmd = `node ${path.relative(process.cwd(), launcher)}`;
+			} else {
+				cmd = dest === 'build' ? 'npx sapper start' : `npx sapper start ${dest}`;
+			}
+
+			console.error(`\n> Finished in ${elapsed(start)}. Type ${clorox.bold.cyan(cmd)} to run the app.`);
 		} catch (err) {
 			console.error(err ? err.details || err.stack || err.message || err : 'Unknown error');
 		}

test/app/start.js

@@ -0,0 +1,7 @@
+// generated by sapper build at 2018-05-04T03:03:00.914Z
+process.env.NODE_ENV = process.env.NODE_ENV || 'production';
+process.env.SAPPER_DEST = require('path').resolve(__dirname, 'build');
+process.env.PORT = process.env.PORT || 3000;
+
+console.log('Starting server on port ' + process.env.PORT);
+require('./build/server.js');

test/common/test.js

@@ -1,3 +1,4 @@
+const fs = require('fs');
 const path = require('path');
 const assert = require('assert');
 const Nightmare = require('nightmare');
@@ -38,6 +39,7 @@ describe('sapper', function() {
 	rimraf.sync('export');
 	rimraf.sync('build');
 	rimraf.sync('.sapper');
+	rimraf.sync('start.js');
 
 	this.timeout(process.env.CI ? 30000 : 10000);
 
@@ -148,7 +150,7 @@ function run({ mode, basepath = '' }) {
 
 		before(() => {
 			const promise = mode === 'production'
-				? exec(`node ${cli} build`).then(() => ports.find(3000))
+				? exec(`node ${cli} build -l`).then(() => ports.find(3000))
 				: ports.find(3000).then(port => {
 					exec(`node ${cli} dev`);
 					return ports.wait(port).then(() => port);
@@ -160,6 +162,10 @@ function run({ mode, basepath = '' }) {
 
 				const dir = mode === 'production' ? 'build' : '.sapper';
 
+				if (mode === 'production') {
+					assert.ok(fs.existsSync('start.js'));
+				}
+
 				proc = require('child_process').fork(`${dir}/server.js`, {
 					cwd: process.cwd(),
 					env: {