assert: use SameValueZero in deepStrictEqual

Comparing NaN will not throw anymore.

PR-URL: https://github.com/nodejs/node/pull/15036
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/assert.md

@@ -107,6 +107,9 @@ parameter is undefined, a default error message is assigned.
 <!-- YAML
 added: v1.2.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/15036
+    description: NaN is now compared using the [SameValueZero][] comparison.
   - version: REPLACEME
     pr-url: https://github.com/nodejs/node/pull/15001
     description: Error names and messages are now properly compared
@@ -129,9 +132,10 @@ changes:
 
 Generally identical to `assert.deepEqual()` with three exceptions:
 
-1. Primitive values are compared using the [Strict Equality Comparison][]
-  ( `===` ). Set values and Map keys are compared using the [SameValueZero][]
-  comparison. (Which means they are free of the [caveats][]).
+1. Primitive values besides `NaN` are compared using the [Strict Equality
+   Comparison][] ( `===` ). Set and Map values, Map keys and `NaN` are compared
+   using the [SameValueZero][] comparison (which means they are free of the
+   [caveats][]).
 2. [`[[Prototype]]`][prototype-spec] of objects are compared using
   the [Strict Equality Comparison][] too.
 3. [Type tags][Object.prototype.toString()] of objects should be the same.
@@ -164,6 +168,8 @@ assert.deepEqual(date, fakeDate);
 assert.deepStrictEqual(date, fakeDate);
 // AssertionError: 2017-03-11T14:25:31.849Z deepStrictEqual Date {}
 // Different type tags
+assert.deepStrictEqual(NaN, NaN);
+// OK, because of the SameValueZero comparison
 ```
 
 If the values are not equal, an `AssertionError` is thrown with a `message`
@@ -412,6 +418,9 @@ parameter is undefined, a default error message is assigned.
 <!-- YAML
 added: v1.2.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/15036
+    description: NaN is now compared using the [SameValueZero][] comparison.
   - version: REPLACEME
     pr-url: https://github.com/nodejs/node/pull/15001
     description: Error names and messages are now properly compared

lib/assert.js

@@ -167,8 +167,11 @@ function isObjectOrArrayTag(tag) {
 // a) The same built-in type tags
 // b) The same prototypes.
 function strictDeepEqual(actual, expected) {
-  if (actual === null || expected === null ||
-    typeof actual !== 'object' || typeof expected !== 'object') {
+  if (typeof actual !== 'object') {
+    return typeof actual === 'number' && Number.isNaN(actual) &&
+      Number.isNaN(expected);
+  }
+  if (typeof expected !== 'object' || actual === null || expected === null) {
     return false;
   }
   const actualTag = objectToString(actual);

test/parallel/test-assert-deep.js

@@ -466,6 +466,7 @@ assertOnlyDeepEqual(
   assertDeepAndStrictEqual(m3, m4);
 }
 
+// Handle sparse arrays
 assertDeepAndStrictEqual([1, , , 3], [1, , , 3]);
 assertOnlyDeepEqual([1, , , 3], [1, , , 3, , , ]);
 
@@ -481,4 +482,11 @@ assertOnlyDeepEqual([1, , , 3], [1, , , 3, , , ]);
   assertOnlyDeepEqual(err1, {}, assert.AssertionError);
 }
 
+// Handle NaN
+assert.throws(() => { assert.deepEqual(NaN, NaN); }, assert.AssertionError);
+assert.doesNotThrow(() => { assert.deepStrictEqual(NaN, NaN); });
+assert.doesNotThrow(() => { assert.deepStrictEqual({ a: NaN }, { a: NaN }); });
+assert.doesNotThrow(
+  () => { assert.deepStrictEqual([ 1, 2, NaN, 4 ], [ 1, 2, NaN, 4 ]); });
+
 /* eslint-enable */