fix sindresorhus#80: add autoHelpFlags

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 yarn.lock
+.idea/

index.js

@@ -32,6 +32,7 @@ module.exports = (helpMessage, opts) => {
 		input: 'string',
 		help: helpMessage,
 		autoHelp: true,
+		autoHelpFlags: true,
 		autoVersion: true
 	}, opts);
 
@@ -62,6 +63,64 @@ module.exports = (helpMessage, opts) => {
 
 	help = (description ? `\n  ${description}\n` : '') + (help ? `\n${help}\n` : '\n');
 
+	if (opts.autoHelpFlags && opts.flags) {
+		const options = Object.keys(opts.flags).reduce((accum, flag) => {
+			const o = opts.flags[flag];
+			if (Object.prototype.hasOwnProperty.call(o, 'default')) {
+				o.default = o.default.toString();
+			}
+
+			const option = {
+				flag: '',
+				value: '',
+				desc: ''
+			};
+
+			if (flag.length === 1) {
+				o.alias = o.alias || flag;
+			}
+
+			option.flag += o.alias ? `-${o.alias}, ` : ' '.repeat(4);
+			option.flag += `--${flag === '--' ? '' : flag}`;
+			accum.flagMaxLen = Math.max(accum.flagMaxLen, option.flag.length);
+
+			if (flag === '--') {
+				option.value = 'arg(s)';
+			} else if (o.type === 'boolean') {
+				option.value = '[true|false]';
+			} else {
+				option.value = `${o.default ? '[' : ''}<value>${o.default ? ']' : ''}`;
+			}
+			accum.valMaxLen = Math.max(accum.valMaxLen, option.value.length);
+
+			if (flag === '--') {
+				option.desc = 'option/arg separator';
+			} else {
+				if (o.description) {
+					option.desc += o.description;
+				}
+				if (o.default) {
+					option.desc += `${o.description ? '; ' : ''}default ${o.default}`;
+				}
+			}
+
+			accum.entries.push(option);
+			return accum;
+		}, {
+			flagMaxLen: 0,
+			valMaxLen: 0,
+			entries: []
+		});
+
+		if (options.entries.length > 0) {
+			help += redent(options.entries.map(it =>
+				`${it.flag}${' '.repeat(options.flagMaxLen - it.flag.length + 2)}` +
+				`${it.value}${' '.repeat(options.valMaxLen - it.value.length + 2)}` +
+				it.desc
+			).join('\n'), 2);
+		}
+	}
+
 	const showHelp = code => {
 		console.log(help);
 		process.exit(typeof code === 'number' ? code : 2);

test.js

@@ -11,6 +11,7 @@ test('return object', t => {
 			Usage
 			  foo <input>
 		`,
+		autoHelpFlags: false,
 		flags: {
 			unicorn: {alias: 'u'},
 			meow: {default: 'dog'},
@@ -27,6 +28,25 @@ test('return object', t => {
 	t.is(cli.help, indentString('\nCLI app helper\n\nUsage\n  foo <input>\n', 2));
 });
 
+test('return object with arg help', t => {
+	const cli = m({
+		argv: ['foo', '--foo-bar', '-u', 'cat', '--', 'unicorn', 'cake'],
+		flags: {
+			unicorn: {alias: 'u', description: 'Unicorn name'},
+			meow: {default: 'dog', description: 'What to meow'},
+			'--': true
+		}
+	});
+
+	t.is(cli.input[0], 'foo');
+	t.true(cli.flags.fooBar);
+	t.is(cli.flags.meow, 'dog');
+	t.is(cli.flags.unicorn, 'cat');
+	t.deepEqual(cli.flags['--'], ['unicorn', 'cake']);
+	t.is(cli.pkg.name, 'meow');
+	t.is(cli.help, indentString('\nCLI app helper\n\n-u, --unicorn  <value>    Unicorn name\n    --meow     [<value>]  What to meow; default dog\n    --         arg(s)     option/arg separator', 2));
+});
+
 test('support help shortcut', t => {
 	const cli = m(`
 		unicorn
@@ -47,7 +67,7 @@ test('spawn cli and not show version', async t => {
 
 test('spawn cli and show help screen', async t => {
 	const {stdout} = await execa('./fixture.js', ['--help']);
-	t.is(stdout, indentString('\nCustom description\n\nUsage\n  foo <input>\n\n', 2));
+	t.is(stdout, indentString('\nCustom description\n\nUsage\n  foo <input>\n\n-u, --unicorn          <value>    \n    --meow             [<value>]  default dog\n    --camelCaseOption  [<value>]  default foo', 2));
 });
 
 test('spawn cli and not show help screen', async t => {