Rewrite in TypeScript

.gitignore

@@ -2,3 +2,4 @@ node_modules
 build
 yarn.lock
 test-d/build.ts
+.tsimp

package.json

@@ -63,8 +63,14 @@
 		"@rollup/plugin-commonjs": "^25.0.7",
 		"@rollup/plugin-json": "^6.1.0",
 		"@rollup/plugin-node-resolve": "^15.2.3",
+		"@sindresorhus/is": "^6.2.0",
+		"@sindresorhus/tsconfig": "^5.0.0",
+		"@types/common-tags": "^1.8.4",
 		"@types/minimist": "^1.2.5",
-		"ava": "^6.1.1",
+		"@types/node": "18",
+		"@types/stack-utils": "^2.0.3",
+		"@types/yargs-parser": "^21.0.3",
+		"ava": "^6.1.2",
 		"camelcase-keys": "^9.1.3",
 		"common-tags": "^2.0.0-alpha.1",
 		"decamelize": "^6.0.0",
@@ -81,9 +87,11 @@
 		"rollup": "^4.12.0",
 		"rollup-plugin-dts": "^6.1.0",
 		"rollup-plugin-license": "^3.2.0",
+		"rollup-plugin-ts": "^3.4.5",
 		"stack-utils": "^2.0.6",
 		"trim-newlines": "^5.0.0",
 		"tsd": "^0.30.7",
+		"tsimp": "^2.0.11",
 		"type-fest": "^4.10.3",
 		"typescript": "~5.3.3",
 		"xo": "^0.57.0",
@@ -92,10 +100,23 @@
 	"xo": {
 		"rules": {
 			"unicorn/no-process-exit": "off",
-			"unicorn/error-message": "off"
+			"unicorn/error-message": "off",
+			"@typescript-eslint/no-dynamic-delete": "off"
 		},
 		"ignores": [
 			"build"
 		]
+	},
+	"ava": {
+		"extensions": {
+			"ts": "module",
+			"js": true
+		},
+		"nodeArguments": [
+			"--import=tsimp"
+		],
+		"environmentVariables": {
+			"TSIMP_DIAG": "ignore"
+		}
 	}
 }

rollup.config.js

@@ -1,13 +1,14 @@
 import fs from 'node:fs/promises';
+import {defineConfig} from 'rollup';
 import {nodeResolve} from '@rollup/plugin-node-resolve';
 import commonjs from '@rollup/plugin-commonjs';
+import typescript from 'rollup-plugin-ts';
 import json from '@rollup/plugin-json';
 import license from 'rollup-plugin-license';
 import {dts} from 'rollup-plugin-dts';
 import {globby} from 'globby';
 import {createTag, replaceResultTransformer} from 'common-tags';
 import {delete_comments as deleteComments} from 'delete_comments';
-import {defineConfig} from 'rollup';
 
 /** Matches empty lines: https://stackoverflow.com/q/16369642/10292952 */
 const emptyLineRegex = /^\s*[\r\n]/gm;
@@ -21,7 +22,9 @@ const sourceDirectory = 'source';
 const outputDirectory = 'build';
 
 const config = defineConfig({
-	input: await globby(`${sourceDirectory}/**/*.js`),
+	input: await globby(`./${sourceDirectory}/**/*.ts`, {
+		ignore: [`./${sourceDirectory}/*.d.ts`, `./${sourceDirectory}/types.ts`],
+	}),
 	output: {
 		dir: outputDirectory,
 		interop: 'esModule',
@@ -51,6 +54,9 @@ const config = defineConfig({
 			include: 'node_modules/**',
 		}),
 		json(),
+		typescript({
+			tsconfig: resolvedConfig => ({...resolvedConfig, declaration: false}),
+		}),
 		license({
 			thirdParty: {
 				output: `${outputDirectory}/licenses.md`,
@@ -60,7 +66,7 @@ const config = defineConfig({
 });
 
 const dtsConfig = defineConfig({
-	input: `./${sourceDirectory}/index.d.ts`,
+	input: `./${sourceDirectory}/index.ts`,
 	output: {
 		file: `./${outputDirectory}/index.d.ts`,
 		format: 'es',
@@ -73,9 +79,10 @@ const dtsConfig = defineConfig({
 			name: 'copy-tsd',
 			async generateBundle() {
 				let tsdFile = await fs.readFile('./test-d/index.ts', 'utf8');
+
 				tsdFile = tsdFile.replace(
-					`import meow from '../${sourceDirectory}/index.js'`,
-					`import meow from '../${outputDirectory}/index.js'`,
+					`../${sourceDirectory}/index.js`,
+					`../${outputDirectory}/index.js`,
 				);
 
 				await fs.writeFile(`./test-d/${outputDirectory}.ts`, tsdFile);

source/index.ts

@@ -0,0 +1,154 @@
+import process from 'node:process';
+import parseArguments, {type Options as ParserOptions} from 'yargs-parser';
+import camelCaseKeys from 'camelcase-keys';
+import {trimNewlines} from 'trim-newlines';
+import redent from 'redent';
+import {buildOptions} from './options.js';
+import {buildParserOptions} from './parser.js';
+import {validate, checkUnknownFlags, checkMissingRequiredFlags} from './validate.js';
+import type {
+	Options,
+	ParsedOptions,
+	Result,
+	AnyFlags,
+} from './types.js';
+
+const buildResult = <Flags extends AnyFlags = AnyFlags>({pkg: packageJson, ...options}: ParsedOptions, parserOptions: ParserOptions): Result<Flags> => {
+	const {_: input, ...argv} = parseArguments(options.argv as string[], parserOptions);
+	let help = '';
+
+	if (options.help) {
+		help = trimNewlines((options.help || '').replace(/\t+\n*$/, ''));
+
+		if (help.includes('\n')) {
+			help = redent(help, options.helpIndent);
+		}
+
+		help = `\n${help}`;
+	}
+
+	if (options.description !== false) {
+		let {description} = options;
+
+		if (description) {
+			description = help ? redent(`\n${description}\n`, options.helpIndent) : `\n${description}`;
+			help = `${description}${help}`;
+		}
+	}
+
+	help += '\n';
+
+	const showHelp = (code?: number) => {
+		console.log(help);
+		process.exit(typeof code === 'number' ? code : 2); // Default to code 2 for incorrect usage (#47)
+	};
+
+	const showVersion = () => {
+		console.log(options.version);
+		process.exit(0);
+	};
+
+	if (input.length === 0 && options.argv.length === 1) {
+		if (argv['version'] === true && options.autoVersion) {
+			showVersion();
+		} else if (argv['help'] === true && options.autoHelp) {
+			showHelp(0);
+		}
+	}
+
+	if (!options.allowUnknownFlags) {
+		checkUnknownFlags(input);
+	}
+
+	const flags = camelCaseKeys(argv, {exclude: ['--', /^\w$/]});
+	const unnormalizedFlags = {...flags};
+
+	validate(flags, options);
+
+	for (const flagValue of Object.values(options.flags)) {
+		if (Array.isArray(flagValue.aliases)) {
+			for (const alias of flagValue.aliases) {
+				delete flags[alias];
+			}
+		}
+
+		if (flagValue.shortFlag) {
+			delete flags[flagValue.shortFlag];
+		}
+	}
+
+	checkMissingRequiredFlags(options.flags, flags, input as string[]);
+
+	const result = {
+		input,
+		flags,
+		unnormalizedFlags,
+		pkg: packageJson,
+		help,
+		showHelp,
+		showVersion,
+	};
+
+	return result as unknown as Result<Flags>;
+};
+
+/**
+@param helpMessage - Shortcut for the `help` option.
+
+@example
+```
+#!/usr/bin/env node
+import meow from 'meow';
+import foo from './index.js';
+
+const cli = meow(`
+	Usage
+	  $ foo <input>
+
+	Options
+	  --rainbow, -r  Include a rainbow
+
+	Examples
+	  $ foo unicorns --rainbow
+	  🌈 unicorns 🌈
+`, {
+	importMeta: import.meta, // This is required
+	flags: {
+		rainbow: {
+			type: 'boolean',
+			shortFlag: 'r'
+		}
+	}
+});
+
+//{
+//	input: ['unicorns'],
+//	flags: {rainbow: true},
+//	...
+//}
+
+foo(cli.input.at(0), cli.flags);
+```
+*/
+export default function meow<Flags extends AnyFlags>(helpMessage: string, options: Options<Flags>): Result<Flags>;
+export default function meow<Flags extends AnyFlags>(options: Options<Flags>): Result<Flags>;
+
+export default function meow<Flags extends AnyFlags = AnyFlags>(helpMessage: string | Options<Flags>, options?: Options<Flags>): Result<Flags> {
+	if (typeof helpMessage !== 'string') {
+		options = helpMessage;
+		helpMessage = '';
+	}
+
+	const parsedOptions = buildOptions(helpMessage, options!);
+	const parserOptions = buildParserOptions(parsedOptions);
+	const result = buildResult<Flags>(parsedOptions, parserOptions);
+
+	const packageTitle = result.pkg.bin ? Object.keys(result.pkg.bin).at(0) : result.pkg.name;
+
+	// TODO: move to separate PR?
+	if (packageTitle) {
+		process.title = packageTitle;
+	}
+
+	return result;
+}