[Fix] do not be tricked by fake Booleans

Fixes #25

Author: ljharb

index.js

@@ -24,5 +24,5 @@ module.exports = function isBoolean(value) {
 	if (value === null || typeof value !== 'object') {
 		return false;
 	}
-	return hasToStringTag && Symbol.toStringTag in value ? tryBooleanObject(value) : $toString(value) === boolClass;
+	return hasToStringTag ? tryBooleanObject(value) : $toString(value) === boolClass;
 };

package.json

@@ -47,6 +47,7 @@
 		"@ljharb/eslint-config": "^21.1.1",
 		"@ljharb/tsconfig": "^0.2.3",
 		"@types/core-js": "^2.5.8",
+		"@types/object-inspect": "^1.13.0",
 		"@types/tape": "^5.8.1",
 		"auto-changelog": "^2.5.0",
 		"core-js": "^3.40.0",
@@ -56,6 +57,7 @@
 		"in-publish": "^2.0.1",
 		"npmignore": "^0.3.1",
 		"nyc": "^10.3.2",
+		"object-inspect": "^1.13.4",
 		"safe-publish-latest": "^2.0.0",
 		"tape": "^5.9.0",
 		"typescript": "next"

test/index.js

@@ -1,8 +1,10 @@
 'use strict';
 
 var test = require('tape');
-var isBoolean = require('../');
 var hasToStringTag = require('has-tostringtag/shams')();
+var inspect = require('object-inspect');
+
+var isBoolean = require('../');
 
 test('not Booleans', function (t) {
 	t.test('primitives', function (st) {
@@ -48,3 +50,24 @@ test('Booleans', function (t) {
 	t.ok(isBoolean(Object(false)), 'Object(false) is Boolean');
 	t.end();
 });
+
+test('Proxy', { skip: typeof Proxy !== 'function' || !hasToStringTag }, function (t) {
+	/** @type {Record<PropertyKey, unknown>} */
+	var target = {};
+	target[Symbol.toStringTag] = 'Boolean';
+	var fake = new Proxy(target, { has: function () { return false; } });
+
+	t.equal(
+		isBoolean(target),
+		false,
+		inspect(target) + ' is not a Boolean'
+	);
+
+	t.equal(
+		isBoolean(fake),
+		false,
+		inspect(fake) + ' is not a Boolean'
+	);
+
+	t.end();
+});