util: fix inspect performance bug

In case an object contained a circular reference `Object.keys` was
called even though it was not necessary at all. This caused a
significant overhead for objects that contained a lot of such entries.

PR-URL: #20007
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>

lib/util.js

@@ -456,6 +456,11 @@ function formatValue(ctx, value, recurseTimes, ln) {
     }
   }
 
+  // Using an array here is actually better for the average case than using
+  // a Set. `seen` will only check for the depth and will never grow too large.
+  if (ctx.seen.indexOf(value) !== -1)
+    return ctx.stylize('[Circular]', 'special');
+
   let keys;
   let symbols = Object.getOwnPropertySymbols(value);
 
@@ -640,11 +645,6 @@ function formatValue(ctx, value, recurseTimes, ln) {
     }
   }
 
-  // Using an array here is actually better for the average case than using
-  // a Set. `seen` will only check for the depth and will never grow too large.
-  if (ctx.seen.indexOf(value) !== -1)
-    return ctx.stylize('[Circular]', 'special');
-
   if (recurseTimes != null) {
     if (recurseTimes < 0)
       return ctx.stylize(`[${constructor || tag || 'Object'}]`, 'special');