Remove ESM generated code

## Details

- This PR basically reverts PR #32 because this is hell. More about this in **Why???** section below.
- Only generate CommonJS code in `lib/` instead of both ESM and CommonJS code.
- Remove Babel stuff and rely on `tsc` to generate CommonJS code and TypeScript declaration files in `lib/`.

## Why???

- Because this is hell. Totally hell.
- Before this PR, rtp.js can not be used in TypeScript projects that use Webpack to generate a bundled JS file. Why? Because Webpack assumes that everything is CommonJS but then it miserably fails to locate/resolve '.cjs' files.
- If we have '.ts' files in `src/` folder, then `tsc` will generate 'js' files rather than '.mjs' files, and that means problems with loaders/bundlers that assume that '.js' files contain CommonJS and then they fail to process them because those '.js'  files contain 'import/export' rather than 'require/module.exports'.
- And if we have '.mts' files in `src` then `tsc` will generate `.mjs` with ESM code but it's literally impossible to have another `tsconfig-cjs.json` file to make `tsc` generate CommonJS code.
- So then we moved to Babel to generate ESM and CJS code (see PR #32), and we have to include tricks to replace the extension in the `import` and `require()` calls in the generated ESM and CJS code in `lib/`, which is terrible. But then Babel also generates `.js.map` files that reference a `.mts` file in `lib/` folder which obviously doesn't exist.
- And another problem is that Babel only generates JavaScript code so we still need to use `tsc` to generate TypeScript declaration files and, since we have '.mts' files in `src/`, those declaration files have `d.mts` extension. But they many text editors and TypeScript consumers asusme that declaraion files must be '.d.ts' only. And if we rename their extension then we have also to munge generated `.mjs` (ESM) and `.cjs` files in `lib/` because those files contain special commented mapping lines that reference the declaration file (with '.d.mts').
- And then it also happens that in CommonJS importing a file without extendion is ok, but in ESM you must write `import foo from './foo.ts'` rather than `from './foo'`. So here another needed rewrite in generated `lib/` code.
- etc etc etc, and **trust me**, more etc etc etc. I've tried EVERYTHING, much more than what I've told here.

## Conclusion

- It's impossible to generate ESM and CJS file in a proper way because it entirely affects the way the TypeScript code must be written, and it includes whether to use `.ts` or `.mts` extension in source files, whether to import internal files with or without extension, and `tsconfig.json` doesn't expose options enough to cover all cases we need when generating ESM or CJS code. I've checked them all, and the same with Babel.
- My conclusion is that, if you want to publish a library in ESM format, you only generate ESM code ('.mjs' files) from TypeScript '.mts' files. But you cannot generate **also** CJS files. And the other way around.

Author: ibc

README.md

@@ -78,7 +78,7 @@ npm install rtp.js
   // Using ESM:
   import { packets as rtpJsPackets, utils as rtpJsUtils } from 'rtp.js';
 
-  // Using CJS:
+  // Using CommonJS:
   const { packets: rtpJsPackets, utils: rtpJsUtils } = require('rtp.js');
 
   const { RtpPacket /* etc. */ } = rtpJsPackets;

babel.config-cjs.mjs

@@ -107,21 +107,21 @@ const config = tsEslint.config(
 			yoda: 2,
 		},
 	},
-	// NOTE: We need to apply this only to .mts source files (and not to .mjs
+	// NOTE: We need to apply this only to .ts source files (and not to .mjs
 	// files).
 	...tsEslint.configs.recommendedTypeChecked.map(item => ({
 		...item,
-		files: ['src/**/*.mts'],
+		files: ['src/**/*.ts'],
 	})),
-	// NOTE: We need to apply this only to .mts source files (and not to .mjs
+	// NOTE: We need to apply this only to .ts source files (and not to .mjs
 	// files).
 	...tsEslint.configs.stylisticTypeChecked.map(item => ({
 		...item,
-		files: ['src/**/*.mts'],
+		files: ['src/**/*.ts'],
 	})),
 	{
-		name: '.mts source files',
-		files: ['src/**/*.mts'],
+		name: '.ts source files',
+		files: ['src/**/*.ts'],
 		languageOptions: {
 			parserOptions: {
 				projectService: true,
@@ -165,9 +165,9 @@ const config = tsEslint.config(
 		},
 	},
 	{
-		name: '.mts test files',
+		name: '.ts test files',
 		...jestEslint.configs['flat/recommended'],
-		files: ['src/test/**/*.mts'],
+		files: ['src/test/**/*.ts'],
 		rules: {
 			...jestEslint.configs['flat/recommended'].rules,
 			'jest/no-disabled-tests': 2,

babel.config-esm.mjs

@@ -1,21 +1,11 @@
 const config = {
 	verbose: true,
 	testEnvironment: 'node',
-	testRegex: 'src/test/.*.test.mts',
-	// Make Jest consider .mts files as if they were ES modules.
-	moduleFileExtensions: ['mts', 'mjs', 'js', 'ts'],
+	testRegex: 'src/test/.*.test.ts',
 	transform: {
-		'^.+\\.mts?$': [
-			'babel-jest',
-			{
-				// We need special Babel settings for Jest plust we need it to be in
-				// a CJS configuration file, otherwise old versions of Node will fail
-				// to run Jest.
-				configFile: './babel.config-jest.cjs',
-			},
-		],
+		'^.+\\.ts?$': ['ts-jest'],
 	},
-	coveragePathIgnorePatterns: ['src/Logger.mts', 'src/test'],
+	coveragePathIgnorePatterns: ['src/Logger.ts', 'src/test'],
 	cacheDirectory: '.cache/jest',
 };
 

babel.config-jest.cjs

@@ -7,9 +7,6 @@ const RELEASE_BRANCH = 'master';
 
 // Paths for ESLint to check. Converted to string for convenience.
 const ESLINT_PATHS = [
-	'babel.config-cjs.mjs',
-	'babel.config-esm.mjs',
-	'babel.config-jest.cjs',
 	'eslint.config.mjs',
 	'jest.config.mjs',
 	'npm-scripts.mjs',
@@ -25,9 +22,6 @@ const ESLINT_IGNORE_PATTERN_ARGS = []
 // Paths for Prettier to check/write. Converted to string for convenience.
 const PRETTIER_PATHS = [
 	'README.md',
-	'babel.config-cjs.mjs',
-	'babel.config-esm.mjs',
-	'babel.config-jest.cjs',
 	'eslint.config.mjs',
 	'jest.config.mjs',
 	'npm-scripts.mjs',
@@ -161,50 +155,20 @@ function buildTypescript() {
 
 	deleteLib();
 
-	// Generate .mjs ESM files in lib/.
-	executeCmd(
-		'babel ./src --config-file "./babel.config-esm.mjs" --out-dir "./lib" --ignore "./src/test/**" --extensions .mts --out-file-extension .mjs --source-maps true'
-	);
-
-	// Generate .cjs CJS files in lib/.
-	executeCmd(
-		'babel ./src --config-file "./babel.config-cjs.mjs" --out-dir "./lib" --ignore "./src/test/**" --extensions .mts --out-file-extension .cjs --source-maps true'
-	);
-
-	// Generate .d.mts TypeScript declaration files in lib/.
+	// Generate .js CommonJS code and .d.ts TypeScript declaration files in lib/.
 	executeCmd('tsc');
 
-	// Delete generated TypeScript declaration files in lib/test/ because we don't
-	// want to expose them.
+	// Delete generated lib/test because we don't to expose them in the published
+	// library.
 	fs.rmSync('lib/test', { recursive: true, force: true });
 }
 
 async function watchTypescript() {
 	logInfo('watchTypescript()');
 
-	// NOTE: Load dep on demand since it's a devDependency.
-	const { concurrently } = await import('concurrently');
-
 	deleteLib();
 
-	concurrently([
-		// Generate .mjs ESM files in lib/ and watch for changes.
-		{
-			name: 'babel ESM',
-			command:
-				'babel ./src --config-file "./babel.config-esm.mjs" --out-dir "./lib" --ignore "./src/test/**" --extensions .mts --out-file-extension .mjs --source-maps true --watch',
-			raw: true,
-		},
-		// Generate .cjs CJS files in lib/ and watch for changes.
-		{
-			name: 'babel CJS',
-			command:
-				'babel ./src --config-file "./babel.config-cjs.mjs" --out-dir "./lib" --ignore "./src/test/**" --extensions .mts --out-file-extension .cjs --source-maps true --watch',
-			raw: true,
-		},
-		// Generate .d.mts TypeScript declaration files in lib/ and watch for changes.
-		{ name: 'tsc', command: 'tsc --watch', prefixColors: 'auto', raw: true },
-	]);
+	executeCmd('tsc --watch');
 }
 
 function lint() {