test(utils): Add tests for importStar(…)

test/utils.test.js

@@ -0,0 +1,128 @@
+// eslint-disable-next-line spaced-comment
+/// <reference path="C:/Users/ExE-Boss/AppData/Local/Microsoft/TypeScript/3.7/node_modules/@types/jest/index.d.ts"/>
+/* eslint-env node, jest */
+/* global BigInt */
+
+"use strict";
+
+const utils = require("../lib/output/utils");
+
+describe("utils.js", () => {
+  describe("importStar", () => {
+    test("importStar works on non-ES2015 modules", () => {
+      const exports = class Foo {
+        static doStuff() {
+          return "success";
+        }
+      };
+
+      exports.init = function (instance, privateData) {
+        instance._privateData = privateData;
+      };
+
+      const Impl = utils.importStar(exports);
+
+      expect(Impl).not.toBe(exports);
+      expect(Impl).not.toHaveProperty("prototype");
+      expect(Impl).not.toHaveProperty("doStuff");
+      expect(Impl).toHaveProperty("default");
+      expect(Impl).toHaveProperty("init");
+      expect(Impl).not.toHaveProperty("__esModule");
+
+      expect(Impl.default).toBe(exports);
+      expect(Impl.init).toBe(exports.init);
+    });
+
+    test("importStar works on ES2015 modules", () => {
+      const module = {};
+      Object.defineProperty(module, "__esModule", { value: true });
+
+      module.default = class Foo {
+        static doStuff() {
+          return "success";
+        }
+      };
+
+      module.init = function (instance, privateData) {
+        instance._privateData = privateData;
+      };
+
+      const Impl = utils.importStar(module);
+
+      expect(Impl).toBe(module);
+      expect(Impl).toHaveProperty("default");
+      expect(Impl).toHaveProperty("init");
+      expect(Impl).toHaveProperty("__esModule");
+    });
+
+    test("importStar caches the result for Object types", () => {
+      const exports = class Foo {
+        static doStuff() {
+          return "success";
+        }
+      };
+
+      const Impl1 = utils.importStar(exports);
+      const Impl2 = utils.importStar(exports);
+
+      expect(Impl1).toBe(Impl2);
+    });
+
+    test("importStar doesn't cache the result for primitive values", () => {
+      const exports = 12345;
+
+      const Impl1 = utils.importStar(exports);
+      const Impl2 = utils.importStar(exports);
+
+      expect(Impl1).not.toBe(Impl2);
+      expect(Impl1.default).toBe(Impl2.default);
+    });
+
+    describe("importStar works on primitive values:", () => {
+      const BIG_INT_PLACEHOLDER = "BigInt placeholder";
+
+      /** @type {Array<string | number | bigint | boolean | symbol | null | undefined>} */
+      const primitives = [
+        123,
+        "string",
+        Symbol.iterator,
+        true,
+        BIG_INT_PLACEHOLDER,
+        null,
+        undefined
+      ];
+
+      // eslint-disable-next-line new-cap, valid-typeof
+      if (typeof BigInt === "function" && typeof BigInt("123") === "bigint") {
+        primitives.splice(
+          primitives.indexOf(BIG_INT_PLACEHOLDER),
+          1,
+          // eslint-disable-next-line new-cap
+          BigInt("123")
+        );
+      }
+
+      for (const primitive of primitives) {
+        /** @type {"string" | "number" | "bigint" | "boolean" | "symbol" | "null" | "undefined"} */
+        let type = primitive === null ? "null" : typeof primitive;
+
+        let testPrimitive = test;
+
+        if (primitive === BIG_INT_PLACEHOLDER) {
+          // BigInt doesn't exist on Node 8, so we have to assign this manually:
+          type = "bigint";
+          testPrimitive = test.skip;
+        }
+
+        testPrimitive(type, () => {
+          const Impl = utils.importStar(primitive);
+
+          expect(Impl).toEqual(expect.anything());
+          expect(Impl).toHaveProperty("default");
+          expect(typeof Impl.default).toEqual(typeof primitive);
+          expect(Impl.default).toEqual(primitive);
+        });
+      }
+    });
+  });
+});