Setup to native ESM

jest.config.js

@@ -1,10 +1,26 @@
-module.exports = {
+export default {
   roots: ['<rootDir>'],
   testMatch: [
     '**/__tests__/**/*.+(ts|tsx|js)',
     '**/?(*.)+(spec|test).+(ts|tsx|js)'
   ],
-  transform: {
-    '^.+\\.(ts|tsx)$': 'ts-jest'
+  collectCoverage: true,
+  collectCoverageFrom: ['<rootDir>/src/**/*.ts'],
+  coveragePathIgnorePatterns: [
+    '<rootDir>/node_modules/',
+    '<rootDir>/src/types/'
+  ],
+  transform: {},
+  testEnvironment: 'jest-environment-node',
+  // https://kulshekhar.github.io/ts-jest/docs/next/guides/esm-support/
+  preset: 'ts-jest/presets/default-esm',
+  extensionsToTreatAsEsm: ['.ts'],
+  globals: {
+    'ts-jest': {
+      useESM: true
+    }
+  },
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1'
   }
 }

package.json

@@ -5,6 +5,8 @@
   "license": "MIT",
   "keywords": [],
   "main": "dist/index.js",
+  "exports": "./dist/index.js",
+  "type": "module",
   "types": "dist/index.d.ts",
   "files": [
     "dist"
@@ -13,11 +15,10 @@
     "count": "dist/main.js"
   },
   "scripts": {
-    "start": "tsc && node dist/main.js",
-    "start:watch": "nodemon --watch src --ext ts --exec ts-node src/main.ts",
-    "build": "tsc",
-    "test": "jest",
-    "clean": "rm dist/*",
+    "start": "npm run build && node dist/main.js",
+    "build": "npm run clean && tsc && rimraf dist/test && mv dist/src/* dist/ && rimraf dist/src",
+    "test": "node --experimental-vm-modules node_modules/.bin/jest",
+    "clean": "rimraf \"dist/*\"",
     "upgrade-interactive": "npm-check --update",
     "csb:test": "npm test -- --runInBand --watchAll"
   },
@@ -31,6 +32,7 @@
     "jest": "^27.3.1",
     "nodemon": "^2.0.14",
     "npm-check": "^5.9.2",
+    "rimraf": "^3.0.2",
     "ts-jest": "^27.0.7",
     "ts-node": "^10.3.0",
     "typescript": "^4.4.4"

src/cli.ts

@@ -1,5 +1,5 @@
 import { Writable } from 'stream'
-import countChars from './count'
+import countChars from './count.js'
 
 type Opts = {
   filenames: string[]

src/index.ts

@@ -1,2 +1,2 @@
-import countChars from './count'
+import countChars from './count.js'
 export { countChars }

src/main.ts

@@ -1,8 +1,7 @@
 #!/usr/bin/env node
 import yargs from 'yargs'
 import { hideBin } from 'yargs/helpers'
-import cli from './cli'
-
+import cli from './cli.js'
 ;(async () => {
   const argv = await yargs(hideBin(process.argv))
     .scriptName('count')

test/cli.spec.ts

@@ -1,5 +1,6 @@
 import { PassThrough } from 'stream'
-import cli from '../src/cli'
+import { jest } from '@jest/globals'
+import cli from '../src/cli.js'
 
 describe('cli()', () => {
   it('should return stdout with exitcode=0', async () => {
@@ -17,10 +18,10 @@ describe('cli()', () => {
       })
     ).toEqual(0)
     expect(outData.mock.calls.length).toEqual(2)
-    expect(outData.mock.calls[0][0].toString('utf8')).toEqual(
+    expect((outData.mock.calls[0][0] as Buffer).toString('utf8')).toEqual(
       'test/assets/test1.txt: 15 chars\n'
     )
-    expect(outData.mock.calls[1][0].toString('utf8')).toEqual(
+    expect((outData.mock.calls[1][0] as Buffer).toString('utf8')).toEqual(
       'test/assets/test2.txt: 17 chars\n'
     )
     expect(errData.mock.calls.length).toEqual(0)
@@ -40,13 +41,13 @@ describe('cli()', () => {
       })
     ).toEqual(1)
     expect(outData.mock.calls.length).toEqual(1)
-    expect(outData.mock.calls[0][0].toString('utf8')).toEqual(
+    expect((outData.mock.calls[0][0] as Buffer).toString('utf8')).toEqual(
       'test/assets/test1.txt: 15 chars\n'
     )
     expect(errData.mock.calls.length).toEqual(2)
-    expect(errData.mock.calls[0][0].toString('utf8')).toEqual(
+    expect((errData.mock.calls[0][0] as Buffer).toString('utf8')).toEqual(
       "Error: ENOENT: no such file or directory, open 'test/assets/fail.txt'"
     )
-    expect(errData.mock.calls[1][0].toString('utf8')).toEqual('\n')
+    expect((errData.mock.calls[1][0] as Buffer).toString('utf8')).toEqual('\n')
   })
 })

test/count.spec.ts

@@ -1,4 +1,4 @@
-import countChars from '../src/count'
+import countChars from '../src/count.js'
 
 describe('countChars()', () => {
   it('should return count of content', async () => {

tsconfig.json

@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
-    "target": "esnext",
-    "module": "commonjs",
+    "target": "es2020",
+    "module": "esnext",
     "moduleResolution": "node",
     "strict": true,
     "skipLibCheck": true,
@@ -17,6 +17,7 @@
   ],
   "include": [
     "src/**/*.ts",
+    "test/**/*.spec.ts",
     "src/**/*.tsx"
   ]
-}
+}