[Breaking] two objects with different Symbol.toStringTags are not equal

Author: ljharb

index.js

@@ -8,6 +8,7 @@ var isDate = require('is-date-object');
 
 var getTime = Date.prototype.getTime;
 var gPO = Object.getPrototypeOf;
+var objToString = Object.prototype.toString;
 
 function deepEqual(actual, expected, options) {
   var opts = options || {};
@@ -60,6 +61,8 @@ function objEquiv(a, b, opts) {
   // an identical 'prototype' property.
   if (a.prototype !== b.prototype) { return false; }
 
+  if (objToString.call(a) !== objToString.call(b)) { return false; }
+
   if (isArguments(a) !== isArguments(b)) { return false; }
 
   var aIsArray = isArray(a);

package.json

@@ -26,6 +26,7 @@
   "devDependencies": {
     "@ljharb/eslint-config": "^13.1.1",
     "eslint": "^5.16.0",
+    "has-symbols": "^1.0.0",
     "object.assign": "^4.1.0",
     "tape": "^4.11.0"
   },

test/cmp.js

@@ -1,6 +1,7 @@
 var test = require('tape');
 require('./_tape');
 var assign = require('object.assign');
+var hasSymbols = require('has-symbols')();
 
 var equal = require('../');
 
@@ -401,3 +402,20 @@ test('[[Prototypes]]', { skip: !Object.getPrototypeOf }, function (t) {
 
   t.end();
 });
+
+test('toStringTag', { skip: !hasSymbols || !Symbol.toStringTag }, function (t) {
+  var o1 = {};
+  t.equal(Object.prototype.toString.call(o1), '[object Object]', 'o1: Symbol.toStringTag works');
+
+  var o2 = {};
+  t.equal(Object.prototype.toString.call(o2), '[object Object]', 'o2: original Symbol.toStringTag works');
+
+  t.deepEqualTest(o1, o2, 'two normal empty objects', true, true);
+
+  o2[Symbol.toStringTag] = 'jifasnif';
+  t.equal(Object.prototype.toString.call(o2), '[object jifasnif]', 'o2: modified Symbol.toStringTag works');
+
+  t.deepEqualTest(o1, o2, 'two normal empty objects with different toStringTags', false, false);
+
+  t.end();
+});