Support Svelte 3

fixes #546, #551, #552, #554

src/api/build.ts

@@ -9,6 +9,7 @@ import read_template from '../core/read_template';
 import { CompileResult } from '../core/create_compilers/interfaces';
 import { noop } from './utils/noop';
 import validate_bundler from './utils/validate_bundler';
+import { copy_runtime } from './utils/copy_runtime';
 
 type Opts = {
 	cwd?: string;
@@ -26,7 +27,7 @@ export async function build({
 	cwd,
 	src = 'src',
 	routes = 'src/routes',
-	output = '__sapper__',
+	output = 'src/node_modules/@sapper',
 	static: static_files = 'static',
 	dest = '__sapper__/build',
 
@@ -47,6 +48,10 @@ export async function build({
 		throw new Error(`Legacy builds are not supported for projects using webpack`);
 	}
 
+	rimraf.sync(path.join(output, '**/*'));
+	mkdirp.sync(output);
+	copy_runtime(output);
+
 	rimraf.sync(path.join(dest, '**/*'));
 	mkdirp.sync(`${dest}/client`);
 	copy_shimport(dest);
@@ -66,7 +71,7 @@ export async function build({
 
 	const manifest_data = create_manifest_data(routes);
 
-	// create src/manifest/client.js and src/manifest/server.js
+	// create src/node_modules/@sapper/app.mjs and server.mjs
 	create_main_manifests({
 		bundler,
 		manifest_data,

src/api/dev.ts

@@ -15,6 +15,7 @@ import { copy_shimport } from './utils/copy_shimport';
 import { ManifestData, FatalEvent, ErrorEvent, ReadyEvent, InvalidEvent } from '../interfaces';
 import read_template from '../core/read_template';
 import { noop } from './utils/noop';
+import { copy_runtime } from './utils/copy_runtime';
 
 type Opts = {
 	cwd?: string,
@@ -72,7 +73,7 @@ class Watcher extends EventEmitter {
 		cwd = '.',
 		src = 'src',
 		routes = 'src/routes',
-		output = '__sapper__',
+		output = 'src/node_modules/@sapper',
 		static: static_files = 'static',
 		dest = '__sapper__/dev',
 		'dev-port': dev_port,
@@ -144,6 +145,11 @@ class Watcher extends EventEmitter {
 		}
 
 		const { cwd, src, dest, routes, output, static: static_files } = this.dirs;
+
+		rimraf.sync(path.join(output, '**/*'));
+		mkdirp.sync(output);
+		copy_runtime(output);
+
 		rimraf.sync(dest);
 		mkdirp.sync(`${dest}/client`);
 		if (this.bundler === 'rollup') copy_shimport(dest);
@@ -484,7 +490,7 @@ function watch_dir(
 	let watch: any;
 	let closed = false;
 
-	import('cheap-watch').then(CheapWatch => {
+	import('cheap-watch').then(({ default: CheapWatch }) => {
 		if (closed) return;
 
 		watch = new CheapWatch({ dir, filter, debounce: 50 });

src/api/utils/copy_runtime.ts

@@ -0,0 +1,21 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import mkdirp from 'mkdirp';
+
+const runtime = [
+	'app.mjs',
+	'server.mjs',
+	'internal/shared.mjs',
+	'internal/Sapper.html',
+	'internal/layout.html'
+].map(file => ({
+	file,
+	source: fs.readFileSync(path.join(__dirname, `../runtime/${file}`), 'utf-8')
+}));
+
+export function copy_runtime(output: string) {
+	runtime.forEach(({ file, source }) => {
+		mkdirp.sync(path.dirname(`${output}/${file}`));
+		fs.writeFileSync(`${output}/${file}`, source);
+	});
+}