From f32f59978c7b10dbe30355da1e4b4d917c7cd1d4 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 3 Dec 2020 12:12:08 -0500
Subject: [PATCH 1/4] transform exported functions correctly - fixes #224

---
 packages/kit/src/api/dev/loader.js         | 144 ++-------------------
 packages/kit/src/api/dev/transform.js      | 137 ++++++++++++++++++++
 packages/kit/src/api/dev/transform.spec.js |  58 +++++++++
 3 files changed, 205 insertions(+), 134 deletions(-)
 create mode 100644 packages/kit/src/api/dev/transform.js
 create mode 100644 packages/kit/src/api/dev/transform.spec.js

diff --git a/packages/kit/src/api/dev/loader.js b/packages/kit/src/api/dev/loader.js
index 7dc136a8a21d..210bcd70f08f 100644
--- a/packages/kit/src/api/dev/loader.js
+++ b/packages/kit/src/api/dev/loader.js
@@ -1,9 +1,6 @@
 import { URL } from 'url';
 import { resolve, relative } from 'path';
-import * as meriyah from 'meriyah';
-import MagicString from 'magic-string';
-import { extract_names } from 'periscopic';
-import { walk } from 'estree-walker';
+import { transform } from './transform';
 
 // This function makes it possible to load modules from the 'server'
 // snowpack server, for the sake of SSR
@@ -47,7 +44,6 @@ export default function loader(snowpack, config) {
 	});
 
 	async function load(url, url_stack) {
-		// TODO: meriyah (JS parser) doesn't support `import.meta.hot = ...` used in HMR setup code.
 		if (url.endsWith('.css.proxy.js')) {
 			return null;
 		}
@@ -75,133 +71,7 @@ export default function loader(snowpack, config) {
 	}
 
 	async function initialize_module(url, data, url_stack) {
-		const code = new MagicString(data);
-		const ast = meriyah.parseModule(data, {
-			ranges: true,
-			next: true
-		});
-
-		const imports = [];
-
-		const export_from_identifiers = new Map();
-		let uid = 1;
-
-		ast.body.forEach((node) => {
-			if (node.type === 'ImportDeclaration') {
-				imports.push(node);
-				code.remove(node.start, node.end);
-			}
-
-			if (node.type === 'ExportAllDeclaration') {
-				if (!export_from_identifiers.has(node.source)) {
-					export_from_identifiers.set(node.source, `__import${uid++}`);
-				}
-
-				code.overwrite(
-					node.start,
-					node.end,
-					`Object.assign(exports, ${export_from_identifiers.get(node.source)})`
-				);
-				imports.push(node);
-			}
-
-			if (node.type === 'ExportDefaultDeclaration') {
-				code.overwrite(node.start, node.declaration.start, 'exports.default = ');
-			}
-
-			if (node.type === 'ExportNamedDeclaration') {
-				if (node.source) {
-					imports.push(node);
-
-					if (!export_from_identifiers.has(node.source)) {
-						export_from_identifiers.set(node.source, `__import${uid++}`);
-					}
-				}
-
-				if (node.specifiers && node.specifiers.length > 0) {
-					code.remove(node.start, node.specifiers[0].start);
-
-					node.specifiers.forEach((specifier) => {
-						const lhs = `exports.${specifier.exported.name}`;
-						const rhs = node.source
-							? `${export_from_identifiers.get(node.source)}.${specifier.local.name}`
-							: specifier.local.name;
-
-						code.overwrite(specifier.start, specifier.end, `${lhs} = ${rhs}`);
-					});
-
-					code.remove(node.specifiers[node.specifiers.length - 1].end, node.end);
-				} else {
-					// `export const foo = ...` or `export function foo() {...}`
-					if (node.declaration.type === 'VariableDeclaration') {
-						code.remove(node.start, node.declaration.start);
-
-						const names = [];
-						node.declaration.declarations.forEach((declarator) => {
-							names.push(...extract_names(declarator.id));
-						});
-
-						code.appendLeft(node.end, names.map((name) => ` exports.${name} = ${name};`).join(''));
-					} else {
-						code.overwrite(
-							node.start,
-							node.declaration.start,
-							`exports.${node.declaration.id.name} = `
-						);
-					}
-				}
-			}
-		});
-
-		// replace import.meta and import(dynamic)
-		if (/import\s*\.\s*meta/.test(data) || /import\s*\(/.test(data)) {
-			walk(ast.body, {
-				enter(node) {
-					if (node.type === 'MetaProperty' && node.meta.name === 'import') {
-						code.overwrite(node.start, node.end, '__importmeta__');
-					} else if (node.type === 'ImportExpression') {
-						code.overwrite(node.start, node.start + 6, '__import__');
-					}
-				}
-			});
-		}
-
-		const deps = [];
-		imports.forEach((node) => {
-			const promise = get_module(url, node.source.value, url_stack);
-
-			if (node.type === 'ExportAllDeclaration' || node.type === 'ExportNamedDeclaration') {
-				// `export * from './other.js'` or `export { foo } from './other.js'`
-				deps.push({
-					name: export_from_identifiers.get(node.source),
-					promise
-				});
-			} else if (node.specifiers.length === 0) {
-				// bare import
-				deps.push({
-					name: null,
-					promise
-				});
-			} else if (node.specifiers[0].type === 'ImportNamespaceSpecifier') {
-				deps.push({
-					name: node.specifiers[0].local.name,
-					promise
-				});
-			} else {
-				deps.push(
-					...node.specifiers.map((specifier) => ({
-						name: specifier.local.name,
-						promise: promise.then(
-							(exports) => exports[specifier.imported ? specifier.imported.name : 'default']
-						)
-					}))
-				);
-			}
-		});
-
-		deps.sort((a, b) => (!!a.name !== !!b.name ? (a.name ? -1 : 1) : 0));
-
-		code.append(`\n//# sourceURL=${url}`);
+		const { code, deps } = transform(url, data);
 
 		const fn = new Function(
 			'exports',
@@ -210,9 +80,15 @@ export default function loader(snowpack, config) {
 			'__import__',
 			'__importmeta__',
 			...deps.map((d) => d.name).filter(Boolean),
-			code.toString()
+			`${code}\n//# sourceURL=${url}`
 		);
-		const values = await Promise.all(deps.map((d) => d.promise));
+
+		const promises = deps.map(async (dep) => {
+			const mod = await get_module(url, dep.source);
+			return dep.prop ? mod[dep.prop] : dep;
+		});
+
+		const values = await Promise.all(promises);
 
 		const exports = {};
 
diff --git a/packages/kit/src/api/dev/transform.js b/packages/kit/src/api/dev/transform.js
new file mode 100644
index 000000000000..c96e43d5e8fd
--- /dev/null
+++ b/packages/kit/src/api/dev/transform.js
@@ -0,0 +1,137 @@
+import * as meriyah from 'meriyah';
+import MagicString from 'magic-string';
+import { extract_names } from 'periscopic';
+import { walk } from 'estree-walker';
+
+export function transform(data) {
+	const code = new MagicString(data);
+	const ast = meriyah.parseModule(data, {
+		ranges: true,
+		next: true
+	});
+
+	const imports = [];
+
+	const export_from_identifiers = new Map();
+	let uid = 1;
+
+	ast.body.forEach((node) => {
+		if (node.type === 'ImportDeclaration') {
+			imports.push(node);
+			code.remove(node.start, node.end);
+		}
+
+		if (node.type === 'ExportAllDeclaration') {
+			if (!export_from_identifiers.has(node.source)) {
+				export_from_identifiers.set(node.source, `__import${uid++}`);
+			}
+
+			code.overwrite(
+				node.start,
+				node.end,
+				`Object.assign(exports, ${export_from_identifiers.get(node.source)})`
+			);
+			imports.push(node);
+		}
+
+		if (node.type === 'ExportDefaultDeclaration') {
+			code.overwrite(node.start, node.declaration.start, 'exports.default = ');
+		}
+
+		if (node.type === 'ExportNamedDeclaration') {
+			if (node.source) {
+				imports.push(node);
+
+				if (!export_from_identifiers.has(node.source)) {
+					export_from_identifiers.set(node.source, `__import${uid++}`);
+				}
+			}
+
+			if (node.specifiers && node.specifiers.length > 0) {
+				code.remove(node.start, node.specifiers[0].start);
+
+				node.specifiers.forEach((specifier) => {
+					const lhs = `exports.${specifier.exported.name}`;
+					const rhs = node.source
+						? `${export_from_identifiers.get(node.source)}.${specifier.local.name}`
+						: specifier.local.name;
+
+					code.overwrite(specifier.start, specifier.end, `${lhs} = ${rhs}`);
+				});
+
+				code.remove(node.specifiers[node.specifiers.length - 1].end, node.end);
+			} else {
+				// `export const foo = ...` or `export function foo() {...}`
+				code.remove(node.start, node.declaration.start);
+
+				let suffix;
+
+				if (node.declaration.type === 'VariableDeclaration') {
+					const names = [];
+					node.declaration.declarations.forEach((declarator) => {
+						names.push(...extract_names(declarator.id));
+					});
+
+					suffix = names.map((name) => ` exports.${name} = ${name};`).join('');
+				} else {
+					const { name } = node.declaration.id;
+					suffix = ` exports.${name} = ${name};`;
+				}
+
+				code.appendLeft(node.end, suffix);
+			}
+		}
+	});
+
+	// replace import.meta and import(dynamic)
+	if (/import\s*\.\s*meta/.test(data) || /import\s*\(/.test(data)) {
+		walk(ast.body, {
+			enter(node) {
+				if (node.type === 'MetaProperty' && node.meta.name === 'import') {
+					code.overwrite(node.start, node.end, '__importmeta__');
+				} else if (node.type === 'ImportExpression') {
+					code.overwrite(node.start, node.start + 6, '__import__');
+				}
+			}
+		});
+	}
+
+	const deps = [];
+	imports.forEach((node) => {
+		const source = node.source.value;
+
+		if (node.type === 'ExportAllDeclaration' || node.type === 'ExportNamedDeclaration') {
+			// `export * from './other.js'` or `export { foo } from './other.js'`
+			deps.push({
+				name: export_from_identifiers.get(node.source),
+				prop: null,
+				source
+			});
+		} else if (node.specifiers.length === 0) {
+			// bare import
+			deps.push({
+				name: null,
+				prop: null,
+				source
+			});
+		} else if (node.specifiers[0].type === 'ImportNamespaceSpecifier') {
+			deps.push({
+				name: node.specifiers[0].local.name,
+				prop: null,
+				source
+			});
+		} else {
+			deps.push(
+				...node.specifiers.map((specifier) => ({
+					name: specifier.local.name,
+					prop: specifier.imported ? specifier.imported.name : 'default',
+					source
+				}))
+			);
+		}
+	});
+
+	deps.sort((a, b) => (!!a.name !== !!b.name ? (a.name ? -1 : 1) : 0));
+
+	return { code: code.toString(), deps };
+}
diff --git a/packages/kit/src/api/dev/transform.spec.js b/packages/kit/src/api/dev/transform.spec.js
new file mode 100644
index 000000000000..9f71c2c803af
--- /dev/null
+++ b/packages/kit/src/api/dev/transform.spec.js
@@ -0,0 +1,58 @@
+import { test } from 'uvu';
+import * as assert from 'uvu/assert';
+import { transform } from './transform';
+
+function compare(a, b) {
+	assert.equal(
+		a.replace(/^\t+/gm, '').trim(),
+		b.replace(/^\t+/gm, '').trim(),
+	);
+}
+
+test('extracts imports', () => {
+	const { code, deps } = transform(`
+		import './empty.js';
+		import foo from './foo.js';
+		import { bar } from './bar.js';
+		import * as baz from './baz.js';
+
+		console.log(foo, bar, baz);
+	`);
+
+	compare(code, `
+		console.log(foo, bar, baz);
+	`);
+
+	assert.equal(deps, [
+		{ name: 'foo', prop: 'default', source: './foo.js' },
+		{ name: 'bar', prop: 'bar', source: './bar.js' },
+		{ name: 'baz', prop: null, source: './baz.js' },
+		{ name: null, prop: null, source: './empty.js' }
+	]);
+});
+
+test('transforms exported functions safely', () => {
+	const { code, deps } = transform(`
+		export function foo() {
+			console.log('foo');
+		}
+
+		export function bar() {
+			foo();
+		}
+	`);
+
+	compare(code, `
+		function foo() {
+			console.log('foo');
+		} exports.foo = foo;
+
+		function bar() {
+			foo();
+		} exports.bar = bar;
+	`);
+
+	assert.equal(deps, []);
+});
+
+test.run();

From bc8562c7a8ea11863641c1f2b456e54b4c36c771 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 3 Dec 2020 12:12:46 -0500
Subject: [PATCH 2/4] add changeset

---
 .changeset/tasty-donkeys-wait.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/tasty-donkeys-wait.md

diff --git a/.changeset/tasty-donkeys-wait.md b/.changeset/tasty-donkeys-wait.md
new file mode 100644
index 000000000000..b1e8f9c76395
--- /dev/null
+++ b/.changeset/tasty-donkeys-wait.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Transform exported functions correctly

From 41baacf0f806ad44daa921caad002b2653cdffe5 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 3 Dec 2020 12:16:00 -0500
Subject: [PATCH 3/4] lint

---
 packages/kit/src/api/dev/transform.spec.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/src/api/dev/transform.spec.js b/packages/kit/src/api/dev/transform.spec.js
index 9f71c2c803af..c45daa486326 100644
--- a/packages/kit/src/api/dev/transform.spec.js
+++ b/packages/kit/src/api/dev/transform.spec.js
@@ -5,7 +5,7 @@ import { transform } from './transform';
 function compare(a, b) {
 	assert.equal(
 		a.replace(/^\t+/gm, '').trim(),
-		b.replace(/^\t+/gm, '').trim(),
+		b.replace(/^\t+/gm, '').trim()
 	);
 }
 

From 05d93f053345e446dd119070723f26177267226b Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 3 Dec 2020 12:35:58 -0500
Subject: [PATCH 4/4] fix daft mistakes

---
 packages/kit/src/api/dev/loader.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/kit/src/api/dev/loader.js b/packages/kit/src/api/dev/loader.js
index 210bcd70f08f..ddf1bc9a8f3b 100644
--- a/packages/kit/src/api/dev/loader.js
+++ b/packages/kit/src/api/dev/loader.js
@@ -71,7 +71,7 @@ export default function loader(snowpack, config) {
 	}
 
 	async function initialize_module(url, data, url_stack) {
-		const { code, deps } = transform(url, data);
+		const { code, deps } = transform(data);
 
 		const fn = new Function(
 			'exports',
@@ -84,8 +84,8 @@ export default function loader(snowpack, config) {
 		);
 
 		const promises = deps.map(async (dep) => {
-			const mod = await get_module(url, dep.source);
-			return dep.prop ? mod[dep.prop] : dep;
+			const mod = await get_module(url, dep.source, url_stack);
+			return dep.prop ? mod[dep.prop] : mod;
 		});
 
 		const values = await Promise.all(promises);