fix: channal error when using sync externals function (#8884)

packages/rspack-test-tools/tests/configCases/externals/function-sync/index.js

@@ -0,0 +1,30 @@
+import "./inject";
+
+import foo from "foo";
+import raz from "raz";
+const myos = require("myos");
+const bar = require("bar");
+const baz = require("baz");
+const fn = require("fn");
+const asyncFn = require("asyncFn");
+const external = require("external");
+const external2 = require("external2");
+const external3 = require("external3");
+const external4 = require("external4");
+const external5 = require("external5");
+
+it("should work with array type of externals", function () {
+	expect(foo).toBe("foo");
+	expect(bar).toBe("bar");
+	expect(baz).toBe("baz");
+	expect(raz).toBe("raz");
+	expect(fn).toBe("fn");
+	expect(asyncFn).toBe("asyncFn");
+	expect(typeof myos.constants.errno.EBUSY).toBe("number");
+
+	expect(external).toBe(Array.isArray);
+	expect(external2).toBe(process.version);
+	expect(external3).toBe(globalThis);
+	expect(external4).toBe(global.process.version);
+	expect(external5).toBe("yj");
+});

packages/rspack-test-tools/tests/configCases/externals/function-sync/inject.js

@@ -0,0 +1,3 @@
+global.foo = "foo";
+global.raz = "raz";
+global.obj = { name: "yj" };

packages/rspack-test-tools/tests/configCases/externals/function-sync/rspack.config.js

@@ -0,0 +1,31 @@
+/** @type {import("@rspack/core").Configuration} */
+module.exports = {
+	externals: [
+		"path",
+		"foo",
+		/^raz$/,
+		{
+			bar: "'bar'",
+			baz: "var 'baz'",
+			myos: "commonjs os",
+			external: ["Array", "isArray"],
+			external2: ["commonjs process", "version"],
+			external3: ["var globalThis"],
+			external4: ["global process", "version"],
+			external5: ["this obj", "name"]
+		},
+		function ({ request }) {
+			if (request === "fn") {
+				return "'fn'";
+			}
+		},
+		function ({ request }) {
+			if (request === "asyncFn") {
+				return "'asyncFn'";
+			}
+		}
+	],
+	externalsPresets: {
+		node: false
+	}
+};

packages/rspack/src/builtin-plugin/ExternalsPlugin.ts

@@ -108,16 +108,24 @@ function getRawExternalItem(
 							externalType: type
 						});
 					}
-				) as Promise<ExternalItemValue>;
-				if (promise?.then) {
-					promise.then(
+				) as Promise<ExternalItemValue> | ExternalItemValue | undefined;
+				if ((promise as Promise<ExternalItemValue>)?.then) {
+					(promise as Promise<ExternalItemValue>).then(
 						result =>
 							resolve({
 								result: getRawExternalItemValueFormFnResult(result),
 								externalType: undefined
 							}),
 						e => reject(e)
 					);
+				} else if (item.length === 1) {
+					// No callback and no promise returned, regarded as a synchronous function
+					resolve({
+						result: getRawExternalItemValueFormFnResult(
+							promise as ExternalItemValue | undefined
+						),
+						externalType: undefined
+					});
 				}
 			});
 		};

packages/rspack/src/config/types.ts

@@ -1425,6 +1425,7 @@ export type ExternalItem =
 	| string
 	| RegExp
 	| ExternalItemObjectUnknown
+	| ((data: ExternalItemFunctionData) => ExternalItemValue)
 	| ((
 			data: ExternalItemFunctionData,
 			callback: (

packages/rspack/src/config/zod.ts

@@ -916,6 +916,12 @@ const externalItem = z
 			.function()
 			.args(externalItemFunctionData as z.ZodType<t.ExternalItemFunctionData>)
 			.returns(z.promise(externalItemValue))
+	)
+	.or(
+		z
+			.function()
+			.args(externalItemFunctionData as z.ZodType<t.ExternalItemFunctionData>)
+			.returns(externalItemValue)
 	) satisfies z.ZodType<t.ExternalItem>;
 
 const externals = externalItem