util: use constructor name

When reaching the depth limit util.inspect always prints [Array]
or [Object] no matter if it is a subclass or not.
This fixes it by showing the actual constructor name instead.

PR-URL: #14886
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

lib/util.js

@@ -594,11 +594,9 @@ function formatValue(ctx, value, recurseTimes, ln) {
     return ctx.stylize('[Circular]', 'special');
 
   if (recurseTimes != null) {
-    if (recurseTimes < 0) {
-      if (Array.isArray(value))
-        return ctx.stylize('[Array]', 'special');
-      return ctx.stylize('[Object]', 'special');
-    }
+    if (recurseTimes < 0)
+      return ctx.stylize(`[${constructor ? constructor.name : 'Object'}]`,
+                         'special');
     recurseTimes -= 1;
   }
 

test/parallel/test-util-inspect.js

@@ -994,6 +994,10 @@ if (typeof Symbol !== 'undefined') {
                      'MapSubclass { \'foo\' => 42 }');
   assert.strictEqual(util.inspect(new PromiseSubclass(() => {})),
                      'PromiseSubclass { <pending> }');
+  assert.strictEqual(
+    util.inspect({ a: { b: new ArraySubclass([1, [2], 3]) } }, { depth: 1 }),
+    '{ a: { b: [ArraySubclass] } }'
+  );
 }
 
 // Empty and circular before depth