util: fix iterable types with special prototype

The fallback should only be taken for a null prototype. If an
iterable data type (e.g., Array) has a prototype without
`Symbol.iterator`, just try the best to visualize it as object.

PR-URL: #25457
Fixes: #25451
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/util/inspect.js

@@ -463,28 +463,22 @@ function clazzWithNullPrototype(clazz, name) {
 function noPrototypeIterator(ctx, value, recurseTimes) {
   let newVal;
   if (isSet(value)) {
-    const clazz = Object.getPrototypeOf(value) ||
-      clazzWithNullPrototype(Set, 'Set');
+    const clazz = clazzWithNullPrototype(Set, 'Set');
     newVal = new clazz(setValues(value));
   } else if (isMap(value)) {
-    const clazz = Object.getPrototypeOf(value) ||
-      clazzWithNullPrototype(Map, 'Map');
+    const clazz = clazzWithNullPrototype(Map, 'Map');
     newVal = new clazz(mapEntries(value));
   } else if (Array.isArray(value)) {
-    const clazz = Object.getPrototypeOf(value) ||
-      clazzWithNullPrototype(Array, 'Array');
+    const clazz = clazzWithNullPrototype(Array, 'Array');
     newVal = new clazz(value.length);
   } else if (isTypedArray(value)) {
-    let clazz = Object.getPrototypeOf(value);
-    if (!clazz) {
-      const constructor = findTypedConstructor(value);
-      clazz = clazzWithNullPrototype(constructor, constructor.name);
-    }
+    const constructor = findTypedConstructor(value);
+    const clazz = clazzWithNullPrototype(constructor, constructor.name);
     newVal = new clazz(value);
   }
-  if (newVal) {
+  if (newVal !== undefined) {
     Object.defineProperties(newVal, Object.getOwnPropertyDescriptors(value));
-    return formatValue(ctx, newVal, recurseTimes);
+    return formatRaw(ctx, newVal, recurseTimes);
   }
 }
 
@@ -728,9 +722,11 @@ function formatRaw(ctx, value, recurseTimes, typedArray) {
     } else {
       // The input prototype got manipulated. Special handle these. We have to
       // rebuild the information so we are able to display everything.
-      const specialIterator = noPrototypeIterator(ctx, value, recurseTimes);
-      if (specialIterator) {
-        return specialIterator;
+      if (constructor === null) {
+        const specialIterator = noPrototypeIterator(ctx, value, recurseTimes);
+        if (specialIterator) {
+          return specialIterator;
+        }
       }
       if (isMapIterator(value)) {
         braces = [`[${tag || 'Map Iterator'}] {`, '}'];

test/parallel/test-util-inspect.js

@@ -1853,6 +1853,16 @@ assert.strictEqual(
     util.inspect(new StorageObject()),
     '<[Object: null prototype] {}> {}'
   );
+
+  obj = [1, 2, 3];
+  Object.setPrototypeOf(obj, Number.prototype);
+  assert.strictEqual(inspect(obj), "Number { '0': 1, '1': 2, '2': 3 }");
+
+  Object.setPrototypeOf(obj, Object.create(null));
+  assert.strictEqual(
+    inspect(obj),
+    "<[Object: null prototype] {}> { '0': 1, '1': 2, '2': 3 }"
+  );
 }
 
 // Check that the fallback always works.