Add ESM support

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [14.x, 16.x, 18.x]
+        node-version: [16.x, 18.x, 20.x]
     steps:
       - uses: actions/checkout@v3
       - name: Use Node.js ${{ matrix.node-version }}
@@ -31,7 +31,7 @@ jobs:
         run: npm run test
       - name: Import with CJS
         if: ${{ always() }}
-        run: node smoke-tests/smoke-test-cjs.js
+        run: node smoke-tests/smoke-test-cjs.cjs
       - name: Import with ESM
         if: ${{ always() }}
         run: node smoke-tests/smoke-test-esm.mjs

.github/workflows/release.yml

@@ -17,7 +17,6 @@ jobs:
     env:
       CI: true
       GITHUB_TOKEN: ${{ secrets.ACTION_GITHUB_TOKEN }}
-      NPM_OTP_TOKEN: ${{ github.event.inputs.otp }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
     runs-on: ubuntu-latest
     steps:

.gitignore

@@ -1,5 +1,9 @@
 .idea
-.npmrc
+.vscode
+
+node_modules
+
 coverage
 dist
-node_modules
+
+.npmrc

jest.config.ts

@@ -6,6 +6,9 @@ const config: Config.InitialOptions = {
     "!<rootDir>/lib/__fixtures__/**/*",
   ],
   moduleFileExtensions: ["ts", "js"],
+  moduleNameMapper: {
+    "^(\\.{1,2}/.*)\\.js$": "$1",
+  },
   transform: {
     "^.+\\.ts$": "@swc/jest",
   },

lib/index.spec.ts

@@ -1,6 +1,6 @@
 import path from "node:path";
 
-import { cosmiconfig, cosmiconfigSync } from "cosmiconfig";
+import { cosmiconfig } from "cosmiconfig";
 
 import { TypeScriptLoader } from ".";
 
@@ -46,13 +46,13 @@ describe("TypeScriptLoader", () => {
   });
 
   describe("cosmiconfigSync", () => {
-    it("should load a valid TS file", () => {
-      const cfg = cosmiconfigSync("test", {
+    it("should load a valid TS file", async () => {
+      const cfg = cosmiconfig("test", {
         loaders: {
           ".ts": TypeScriptLoader(),
         },
       });
-      const loadedCfg = cfg.load(
+      const loadedCfg = await cfg.load(
         path.resolve(fixturesPath, "valid.fixture.ts")
       );
 
@@ -61,16 +61,16 @@ describe("TypeScriptLoader", () => {
       expect(loadedCfg!.config.test.cake).toStrictEqual("a lie");
     });
 
-    it("should throw an error on loading an invalid TS file", () => {
-      const cfg = cosmiconfigSync("test", {
+    it("should throw an error on loading an invalid TS file", async () => {
+      const cfg = cosmiconfig("test", {
         loaders: {
           ".ts": TypeScriptLoader(),
         },
       });
 
-      expect(() =>
+      await expect(() =>
         cfg.load(path.resolve(fixturesPath, "invalid.fixture.ts"))
-      ).toThrowError();
+      ).rejects.toThrowError();
     });
   });
 });

lib/index.ts

@@ -1,2 +1,2 @@
-export { TypeScriptLoader } from "./loader";
-export type { TypeScriptCompileError } from "./typescript-compile-error";
+export { TypeScriptLoader } from "./loader.js";
+export type { TypeScriptCompileError } from "./typescript-compile-error.js";

lib/loader.spec.ts

@@ -26,9 +26,11 @@ describe("TypeScriptLoader", () => {
     loader(filePath, readFixtureContent(filePath));
   });
 
-  it("should fail on parsing an invalid TS file", () => {
+  it("should fail on parsing an invalid TS file", async () => {
     const filePath = path.resolve(fixturesPath, "invalid.fixture.ts");
-    expect(() => loader(filePath, readFixtureContent(filePath))).toThrowError();
+    await expect(() =>
+      loader(filePath, readFixtureContent(filePath))
+    ).rejects.toThrowError();
   });
 
   it("should use the same instance of ts-node across multiple calls", () => {
@@ -38,10 +40,10 @@ describe("TypeScriptLoader", () => {
     expect(tsNodeSpy).toHaveBeenCalledTimes(1);
   });
 
-  it("should throw a TypeScriptCompileError on error", () => {
+  it("should throw a TypeScriptCompileError on error", async () => {
     try {
       const filePath = path.resolve(fixturesPath, "invalid.fixture.ts");
-      loader(filePath, readFixtureContent(filePath));
+      await loader(filePath, readFixtureContent(filePath));
       fail(
         "Error should be thrown upon failing to transpile an invalid TS file."
       );
@@ -72,9 +74,9 @@ describe("TypeScriptLoader", () => {
       stub.mockRestore();
     });
 
-    it("rethrows an error if it is not an instance of Error", () => {
+    it("rethrows an error if it is not an instance of Error", async () => {
       try {
-        loader("filePath", "readFixtureContent(filePath)");
+        await loader("filePath", "readFixtureContent(filePath)");
         fail(
           "Error should be thrown upon failing to transpile an invalid TS file."
         );

lib/loader.ts

@@ -1,18 +1,15 @@
 import type { Loader } from "cosmiconfig";
 import { register, RegisterOptions } from "ts-node";
 
-import { TypeScriptCompileError } from "./typescript-compile-error";
+import { TypeScriptCompileError } from "./typescript-compile-error.js";
 
 export function TypeScriptLoader(options?: RegisterOptions): Loader {
-  const tsNodeInstance = register({
-    ...options,
-    compilerOptions: { module: "commonjs" },
-  });
-  return (path: string, content: string) => {
+  const tsNodeInstance = register(options);
+  return async (path: string, content: string) => {
     try {
       // cosmiconfig requires the transpiled configuration to be CJS
       tsNodeInstance.compile(content, path);
-      const result = require(path);
+      const result = await import(path);
 
       // `default` is used when exporting using export default, some modules
       // may still use `module.exports` or if in TS `export = `