Also use import for unresolvable dynamic imports

src/ast/nodes/ImportExpression.ts

@@ -1,6 +1,6 @@
 import type MagicString from 'magic-string';
 import ExternalModule from '../../ExternalModule';
-import type Module from '../../Module';
+import Module from '../../Module';
 import type { GetInterop, NormalizedOutputOptions } from '../../rollup/types';
 import type { PluginDriver } from '../../utils/PluginDriver';
 import type { GenerateCodeSnippets } from '../../utils/generateCodeSnippets';
@@ -157,7 +157,10 @@ export default class ImportExpression extends NodeBase {
 		const hasDynamicTarget = !this.resolution || typeof this.resolution === 'string';
 		switch (format) {
 			case 'cjs': {
-				if (resolution instanceof ExternalModule && dynamicImportInCjs) {
+				if (
+					dynamicImportInCjs &&
+					(!resolution || typeof resolution === 'string' || resolution instanceof ExternalModule)
+				) {
 					return { helper: null, mechanism: null };
 				}
 				const helper = getInteropHelper(resolution, exportMode, interop);

test/form/samples/dynamic-import-unresolvable/_expected/cjs.js

@@ -1,23 +1,6 @@
 'use strict';
 
-function _interopNamespaceDefault(e) {
-	var n = Object.create(null);
-	if (e) {
-		Object.keys(e).forEach(function (k) {
-			if (k !== 'default') {
-				var d = Object.getOwnPropertyDescriptor(e, k);
-				Object.defineProperty(n, k, d.get ? d : {
-					enumerable: true,
-					get: function () { return e[k]; }
-				});
-			}
-		});
-	}
-	n.default = e;
-	return Object.freeze(n);
-}
-
-(function (t) { return Promise.resolve().then(function () { return /*#__PURE__*/_interopNamespaceDefault(require(t)); }); })(`${globalThis.unknown}`);
-(function (t) { return Promise.resolve().then(function () { return /*#__PURE__*/_interopNamespaceDefault(require(t)); }); })(`My ${globalThis.unknown}`);
-(function (t) { return Promise.resolve().then(function () { return /*#__PURE__*/_interopNamespaceDefault(require(t)); }); })('./seven.js');
+import(`${globalThis.unknown}`);
+import(`My ${globalThis.unknown}`);
+import('./seven.js');
 import('./seven.js');