enforce treeshakeability (#9430)

* enforce treeshakeability

* fix

* appease the dweeby little hall monitor

---------

Co-authored-by: Rich Harris <[email protected]>

Author: Rich-Harris

packages/svelte/package.json

@@ -90,7 +90,7 @@
     "templating"
   ],
   "scripts": {
-    "build": "rollup -c && node scripts/build.js",
+    "build": "rollup -c && node scripts/build.js && node scripts/check-treeshakeability.js",
     "watch": "rollup -cw",
     "check": "tsc && cd ./tests/types && tsc",
     "check:watch": "tsc --watch",
@@ -103,6 +103,7 @@
     "@rollup/plugin-commonjs": "^25.0.7",
     "@rollup/plugin-node-resolve": "^15.2.3",
     "@rollup/plugin-terser": "^0.4.4",
+    "@rollup/plugin-virtual": "^3.0.2",
     "@types/aria-query": "^5.0.3",
     "@types/estree": "^1.0.5",
     "dts-buddy": "^0.4.0",

packages/svelte/scripts/check-treeshakeability.js

@@ -0,0 +1,62 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import { rollup } from 'rollup';
+import virtual from '@rollup/plugin-virtual';
+
+const pkg = JSON.parse(fs.readFileSync('package.json', 'utf8'));
+
+let failed = false;
+
+// eslint-disable-next-line no-console
+console.group('checking treeshakeability');
+
+for (const key in pkg.exports) {
+	// special cases
+	if (key === './compiler') continue;
+	if (key === './internal/disclose-version') continue;
+
+	for (const type of ['browser', 'default']) {
+		if (!pkg.exports[key][type]) continue;
+
+		const subpackage = path.join(pkg.name, key);
+
+		const resolved = path.resolve(pkg.exports[key][type]);
+
+		const bundle = await rollup({
+			input: '__entry__',
+			plugins: [
+				virtual({
+					__entry__: `import ${JSON.stringify(resolved)}`
+				})
+			],
+			onwarn: (warning, handle) => {
+				// if (warning.code !== 'EMPTY_BUNDLE') handle(warning);
+			}
+		});
+
+		const { output } = await bundle.generate({});
+
+		if (output.length > 1) {
+			throw new Error('errr what');
+		}
+
+		const code = output[0].code.replace(/import\s+([^'"]+from\s+)?(['"])[^'"]+\2\s*;?/, '');
+		if (code.trim()) {
+			// eslint-disable-next-line no-console
+			console.error(code);
+			// eslint-disable-next-line no-console
+			console.error(`❌ ${subpackage} (${type})`);
+			failed = true;
+		} else {
+			// eslint-disable-next-line no-console
+			console.error(`✅ ${subpackage} (${type})`);
+		}
+	}
+}
+
+// eslint-disable-next-line no-console
+console.groupEnd();
+
+if (failed) {
+	process.exit(1);
+}

packages/svelte/src/internal/server/index.js

@@ -32,7 +32,7 @@ const INVALID_ATTR_NAME_CHAR_REGEX =
 	/[\s'">/=\u{FDD0}-\u{FDEF}\u{FFFE}\u{FFFF}\u{1FFFE}\u{1FFFF}\u{2FFFE}\u{2FFFF}\u{3FFFE}\u{3FFFF}\u{4FFFE}\u{4FFFF}\u{5FFFE}\u{5FFFF}\u{6FFFE}\u{6FFFF}\u{7FFFE}\u{7FFFF}\u{8FFFE}\u{8FFFF}\u{9FFFE}\u{9FFFF}\u{AFFFE}\u{AFFFF}\u{BFFFE}\u{BFFFF}\u{CFFFE}\u{CFFFF}\u{DFFFE}\u{DFFFF}\u{EFFFE}\u{EFFFF}\u{FFFFE}\u{FFFFF}\u{10FFFE}\u{10FFFF}]/u;
 
 // This is duplicated from the compiler, but we need it at runtime too.
-const DOMBooleans = [
+export const DOMBooleanAttributes = [
 	'allowfullscreen',
 	'async',
 	'autofocus',
@@ -59,9 +59,6 @@ const DOMBooleans = [
 	'selected'
 ];
 
-/** @type {Set<string>} */
-export const DOMBooleanAttributes = new Set(DOMBooleans);
-
 export const VoidElements = new Set([
 	'area',
 	'base',
@@ -280,7 +277,7 @@ export function spread_attributes(attrs, class_hash, additional) {
 
 	for (name in merged_attrs) {
 		if (INVALID_ATTR_NAME_CHAR_REGEX.test(name)) continue;
-		const is_boolean = DOMBooleanAttributes.has(name);
+		const is_boolean = DOMBooleanAttributes.includes(name);
 		attr_str += attr(name, merged_attrs[name], is_boolean);
 	}