Find the cost of adding an npm package to your app's bundle size
teardown.kelinci.dev
fix: check for default via AST
+28
-24
+27
-24
src/npm/bundler.ts
+27
-24
src/npm/bundler.ts
···
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const VIRTUAL_ENTRY_ID = '\0virtual:entry';
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/**
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* checks if a file likely has a default export.
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* looks for common patterns in ESM and CJS.
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*/
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function hasDefaultExport(source: string): boolean {
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// ESM patterns
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if (/\bexport\s+default\b/.test(source)) {
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return true;
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}
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if (/\bexport\s*\{\s*[^}]*\bdefault\b/.test(source)) {
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return true;
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}
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// CJS patterns (bundlers typically convert these to default exports)
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if (/\bmodule\.exports\s*=/.test(source)) {
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return true;
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}
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if (/\bexports\.default\s*=/.test(source)) {
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return true;
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}
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return false;
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}
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/**
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* creates a virtual entry point that imports and re-exports from a specific subpath.
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*
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* @param packageName the package name
···
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if (resolved) {
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try {
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const source = volume.readFileSync(resolved.id, 'utf8') as string;
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includeDefault = hasDefaultExport(source);
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const ast = this.parse(source);
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+
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for (const node of ast.body) {
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// export default ...
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if (node.type === 'ExportDefaultDeclaration') {
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includeDefault = true;
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break;
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}
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+
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// export { default } from '...' or export { foo as default }
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if (node.type === 'ExportNamedDeclaration') {
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for (const spec of node.specifiers) {
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const exported = spec.exported;
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const name = exported.type === 'Literal' ? exported.value : exported.name;
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if (name === 'default') {
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includeDefault = true;
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break;
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}
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}
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+
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if (includeDefault) {
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break;
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}
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}
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}
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} catch {
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// couldn't read file, skip default export
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// couldn't read/parse file, skip default export
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}
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}
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}