Keep assertions on fully dynamic imports

src/Chunk.ts

@@ -857,12 +857,12 @@ export default class Chunk {
 	private getDynamicImportStringAndAssertions(
 		resolution: ExternalModule | string | null,
 		fileName: string
-	): [importPath: string, assertions: string | null] {
+	): [importPath: string, assertions: string | null | true] {
 		if (resolution instanceof ExternalModule) {
 			const chunk = this.externalChunkByModule.get(resolution)!;
 			return [`'${chunk.getImportPath(fileName)}'`, chunk.getImportAssertions(this.snippets)];
 		}
-		return [resolution || '', null];
+		return [resolution || '', this.outputOptions.format === 'es' || null];
 	}
 
 	private getFallbackChunkName(): string {

src/ast/nodes/ImportExpression.ts

@@ -29,7 +29,7 @@ export default class ImportExpression extends NodeBase {
 	declare source: ExpressionNode;
 	declare type: NodeType.tImportExpression;
 
-	private assertions: string | null = null;
+	private assertions: string | null | true = null;
 	private mechanism: DynamicImportMechanism | null = null;
 	private namespaceExportName: string | false | undefined = undefined;
 	private resolution: Module | ExternalModule | string | null = null;
@@ -70,34 +70,20 @@ export default class ImportExpression extends NodeBase {
 			code.overwrite(
 				this.start,
 				this.end,
-				`Promise.resolve().then(${left}${this.inlineNamespace.getName(getPropertyAccess)}${right})`,
-				{ contentOnly: true }
+				`Promise.resolve().then(${left}${this.inlineNamespace.getName(getPropertyAccess)}${right})`
 			);
 			return;
 		}
-
-		if (this.arguments) {
-			code.remove(this.source.end, this.end - 1);
-		}
 		if (this.mechanism) {
 			code.overwrite(
 				this.start,
 				findFirstOccurrenceOutsideComment(code.original, '(', this.start + 6) + 1,
-				this.mechanism.left,
-				{ contentOnly: true }
+				this.mechanism.left
 			);
-			code.overwrite(this.end - 1, this.end, this.mechanism.right, { contentOnly: true });
+			code.overwrite(this.end - 1, this.end, this.mechanism.right);
 		}
 		if (this.resolutionString) {
 			code.overwrite(this.source.start, this.source.end, this.resolutionString);
-			if (this.assertions) {
-				code.appendLeft(
-					this.end - 1,
-					`,${_}${getObject([['assert', this.assertions]], {
-						lineBreakIndent: null
-					})}`
-				);
-			}
 			if (this.namespaceExportName) {
 				const [left, right] = getDirectReturnFunction(['n'], {
 					functionReturn: true,
@@ -109,6 +95,19 @@ export default class ImportExpression extends NodeBase {
 		} else {
 			this.source.render(code, options);
 		}
+		if (this.assertions !== true) {
+			if (this.arguments) {
+				code.overwrite(this.source.end, this.end - 1, '', { contentOnly: true });
+			}
+			if (this.assertions) {
+				code.appendLeft(
+					this.end - 1,
+					`,${_}${getObject([['assert', this.assertions]], {
+						lineBreakIndent: null
+					})}`
+				);
+			}
+		}
 	}
 
 	setExternalResolution(
@@ -120,7 +119,7 @@ export default class ImportExpression extends NodeBase {
 		accessedGlobalsByScope: Map<ChildScope, Set<string>>,
 		resolutionString: string,
 		namespaceExportName: string | false | undefined,
-		assertions: string | null
+		assertions: string | null | true
 	): void {
 		const { format } = options;
 		this.inlineNamespace = null;

test/form/samples/import-assertions/keep-dynamic-assertions/_config.js

@@ -0,0 +1,6 @@
+module.exports = {
+	description: 'keep import assertions for non-resolvable dynamic imports',
+	options: {
+		external: true
+	}
+};

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/amd.js

@@ -0,0 +1,22 @@
+define(['require'], (function (require) { '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 new Promise(function (resolve, reject) { require([t], function (m) { resolve(/*#__PURE__*/_interopNamespaceDefault(m)); }, reject); }); })(globalThis.unknown);
+
+}));

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/cjs.js

@@ -0,0 +1,20 @@
+'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);

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/es.js

@@ -0,0 +1 @@
+import(globalThis.unknown, { assert: { type: 'special' } });

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/iife.js

@@ -0,0 +1,6 @@
+(function () {
+	'use strict';
+
+	import(globalThis.unknown);
+
+})();

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/system.js

@@ -0,0 +1,10 @@
+System.register([], (function (exports, module) {
+	'use strict';
+	return {
+		execute: (function () {
+
+			module.import(globalThis.unknown);
+
+		})
+	};
+}));

test/form/samples/import-assertions/keep-dynamic-assertions/_expected/umd.js

@@ -0,0 +1,8 @@
+(function (factory) {
+	typeof define === 'function' && define.amd ? define(factory) :
+	factory();
+})((function () { 'use strict';
+
+	import(globalThis.unknown);
+
+}));

test/form/samples/import-assertions/keep-dynamic-assertions/main.js

@@ -0,0 +1 @@
+import(globalThis.unknown, { assert: { type: 'special' } });