util: improve Symbol.toStringTag handling

Only special handle `Symbol.toStringTag` if the property is not
enumerable or not the own property of the inspected object.
PR-URL: #27342
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: BridgeAR

lib/internal/util/inspect.js

@@ -574,8 +574,15 @@ function formatRaw(ctx, value, recurseTimes, typedArray) {
 
 constconstructor=getConstructorName(value,ctx);
 lettag=value[Symbol.toStringTag];
-if(typeoftag!=='string')
+// Only list the tag in case it's non-enumerable / not an own property.
+// Otherwise we'd print this twice.
+if(typeoftag!=='string'||
+tag!==''&&
+(ctx.showHidden ? hasOwnProperty : propertyIsEnumerable)(
+value,Symbol.toStringTag
+)){
 tag='';
+}
 letbase='';
 letformatter=getEmptyFormatArray;
 letbraces;

test/parallel/test-util-inspect.js

@@ -1267,8 +1267,20 @@ util.inspect(process);
 
 {
 // @@toStringTag
-assert.strictEqual(util.inspect({[Symbol.toStringTag]: 'a'}),
-"Object [a] { [Symbol(Symbol.toStringTag)]: 'a' }");
+constobj={[Symbol.toStringTag]: 'a'};
+assert.strictEqual(
+util.inspect(obj),
+"{ [Symbol(Symbol.toStringTag)]: 'a' }"
+);
+Object.defineProperty(obj,Symbol.toStringTag,{
+value: 'a',
+enumerable: false
+});
+assert.strictEqual(util.inspect(obj),'Object [a] {}');
+assert.strictEqual(
+util.inspect(obj,{showHidden: true}),
+"{ [Symbol(Symbol.toStringTag)]: 'a' }"
+);
 
 classFoo{
 constructor(){