fix: use BigInt for large integers to preserve precision

package.json

@@ -1,6 +1,6 @@
 {
   "name": "mri",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Quickly scan for CLI flags and arguments",
   "repository": "lukeed/mri",
   "module": "lib/index.mjs",

src/index.js

@@ -2,12 +2,21 @@ function toArr(any) {
 	return any == null ? [] : Array.isArray(any) ? any : [any];
 }
 
+function toNum(val) {
+	if (typeof val !== 'string') return val;
+	var x = +val;
+	if (x * 0 !== 0) return val; // NaN check
+	// Only use BigInt for integer strings that lose precision
+	if (String(x) !== val && /^-?\d+$/.test(val)) return BigInt(val);
+	return x;
+}
+
 function toVal(out, key, val, opts) {
 	var x, old=out[key], nxt=(
 		!!~opts.string.indexOf(key) ? (val == null || val === true ? '' : String(val))
 		: typeof val === 'boolean' ? val
-		: !!~opts.boolean.indexOf(key) ? (val === 'false' ? false : val === 'true' || (out._.push((x = +val,x * 0 === 0) ? x : val),!!val))
-		: (x = +val,x * 0 === 0) ? x : val
+		: !!~opts.boolean.indexOf(key) ? (val === 'false' ? false : val === 'true' || (out._.push(toNum(val)),!!val))
+		: toNum(val)
 	);
 	out[key] = old == null ? nxt : (Array.isArray(old) ? old.concat(nxt) : [old, nxt]);
 }

test/num.js

@@ -34,3 +34,32 @@ test('already a number', t => {
 	t.is(typeof argv.x, 'number');
 	t.end();
 });
+
+test('large integers use BigInt to preserve precision', t => {
+	const argv = fn(['--id', '9007199254740993', '--small', '42']);
+	t.is(argv.id, 9007199254740993n);
+	t.is(typeof argv.id, 'bigint');
+	t.is(argv.small, 42);
+	t.is(typeof argv.small, 'number');
+	t.end();
+});
+
+test('MAX_SAFE_INTEGER boundary', t => {
+	// MAX_SAFE_INTEGER = 9007199254740991
+	const argv = fn([
+		'--safe', '9007199254740991',
+		'--unsafe', '9007199254740993'
+	]);
+	t.is(argv.safe, 9007199254740991);
+	t.is(typeof argv.safe, 'number');
+	t.is(argv.unsafe, 9007199254740993n);
+	t.is(typeof argv.unsafe, 'bigint');
+	t.end();
+});
+
+test('large negative integers', t => {
+	const argv = fn(['--id=-9007199254740993']);
+	t.is(argv.id, -9007199254740993n);
+	t.is(typeof argv.id, 'bigint');
+	t.end();
+});