feat(): dedupe accepts a function

index.d.ts

@@ -85,7 +85,7 @@ export interface Options {
 	 * to prevent bundling the same package multiple times if package is
 	 * imported from dependencies.
 	 */
-	dedupe?: string[];
+	dedupe?: string[] | ((importee: string) => boolean);
 
 	/**
 	 * Any additional options that should be passed through

src/index.js

@@ -100,6 +100,13 @@ export default function nodeResolve ( options = {} ) {
 	const extensions = options.extensions || DEFAULT_EXTS;
 	const packageInfoCache = new Map();
 
+	function shouldDedupe (importee) {
+		if (typeof dedupe === 'function') {
+			return !!dedupe(importee);
+		}
+		return dedupe.indexOf(importee) !== -1;
+	}
+
 	function getCachedPackageInfo (pkg, pkgPath) {
 		if (packageInfoCache.has(pkgPath)) {
 			return packageInfoCache.get(pkgPath);
@@ -187,7 +194,7 @@ export default function nodeResolve ( options = {} ) {
 
 			const basedir = importer ? dirname( importer ) : process.cwd();
 
-			if (dedupe.indexOf(importee) !== -1) {
+			if (shouldDedupe(importee)) {
 				importee = join(process.cwd(), 'node_modules', importee);
 			}