util: improve prototype inspection using inspect() and showHidden

The fast path for the prototype inspection had a bug that caused some
prototype properties to be skipped that should in fact be inspected.

Backport-PR-URL: #31431
PR-URL: #31113
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/internal/util/inspect.js

@@ -467,10 +467,10 @@ function getConstructorName(obj, ctx, recurseTimes, protoProps) {
         typeof descriptor.value === 'function' &&
         descriptor.value.name !== '') {
       if (protoProps !== undefined &&
-          !builtInObjects.has(descriptor.value.name)) {
-        const isProto = firstProto !== undefined;
+         (firstProto !== obj ||
+         !builtInObjects.has(descriptor.value.name))) {
         addPrototypeProperties(
-          ctx, tmp, obj, recurseTimes, isProto, protoProps);
+          ctx, tmp, firstProto || tmp, recurseTimes, protoProps);
       }
       return descriptor.value.name;
     }
@@ -508,12 +508,12 @@ function getConstructorName(obj, ctx, recurseTimes, protoProps) {
 // This function has the side effect of adding prototype properties to the
 // `output` argument (which is an array). This is intended to highlight user
 // defined prototype properties.
-function addPrototypeProperties(ctx, main, obj, recurseTimes, isProto, output) {
+function addPrototypeProperties(ctx, main, obj, recurseTimes, output) {
   let depth = 0;
   let keys;
   let keySet;
   do {
-    if (!isProto) {
+    if (depth !== 0 || main === obj) {
       obj = ObjectGetPrototypeOf(obj);
       // Stop as soon as a null prototype is encountered.
       if (obj === null) {
@@ -526,8 +526,6 @@ function addPrototypeProperties(ctx, main, obj, recurseTimes, isProto, output) {
           builtInObjects.has(descriptor.value.name)) {
         return;
       }
-    } else {
-      isProto = false;
     }
 
     if (depth === 0) {

test/parallel/test-util-inspect.js

@@ -1687,7 +1687,8 @@ util.inspect(process);
     '      1,',
     '      2,',
     '      [length]: 2',
-    '    ]',
+    '    ],',
+    "    [Symbol(Symbol.toStringTag)]: 'Set Iterator'",
     '  } => [Map Iterator] {',
     '    Uint8Array(0) [',
     '      [BYTES_PER_ELEMENT]: 1,',
@@ -1699,7 +1700,8 @@ util.inspect(process);
     '        foo: true',
     '      }',
     '    ],',
-    '    [Circular]',
+    '    [Circular],',
+    "    [Symbol(Symbol.toStringTag)]: 'Map Iterator'",
     '  },',
     '  [size]: 2',
     '}'
@@ -1727,15 +1729,19 @@ util.inspect(process);
     '    [byteOffset]: 0,',
     '    [buffer]: ArrayBuffer { byteLength: 0, foo: true }',
     '  ],',
-    '  [Set Iterator] { [ 1, 2, [length]: 2 ] } => [Map Iterator] {',
+    '  [Set Iterator] {',
+    '    [ 1, 2, [length]: 2 ],',
+    "    [Symbol(Symbol.toStringTag)]: 'Set Iterator'",
+    '  } => [Map Iterator] {',
     '    Uint8Array(0) [',
     '      [BYTES_PER_ELEMENT]: 1,',
     '      [length]: 0,',
     '      [byteLength]: 0,',
     '      [byteOffset]: 0,',
     '      [buffer]: ArrayBuffer { byteLength: 0, foo: true }',
     '    ],',
-    '    [Circular]',
+    '    [Circular],',
+    "    [Symbol(Symbol.toStringTag)]: 'Map Iterator'",
     '  },',
     '  [size]: 2',
     '}'
@@ -1767,7 +1773,9 @@ util.inspect(process);
     '  [Set Iterator] {',
     '    [ 1,',
     '      2,',
-    '      [length]: 2 ] } => [Map Iterator] {',
+    '      [length]: 2 ],',
+    '    [Symbol(Symbol.toStringTag)]:',
+    "     'Set Iterator' } => [Map Iterator] {",
     '    Uint8Array(0) [',
     '      [BYTES_PER_ELEMENT]: 1,',
     '      [length]: 0,',
@@ -1776,7 +1784,9 @@ util.inspect(process);
     '      [buffer]: ArrayBuffer {',
     '        byteLength: 0,',
     '        foo: true } ],',
-    '    [Circular] },',
+    '    [Circular],',
+    '    [Symbol(Symbol.toStringTag)]:',
+    "     'Map Iterator' },",
     '  [size]: 2 }'
   ].join('\n');
 
@@ -2678,4 +2688,11 @@ assert.strictEqual(
     '  \x1B[2m[def]: \x1B[36m[Getter/Setter]\x1B[39m\x1B[22m\n' +
     '}'
   );
+
+  const obj = Object.create({ abc: true, def: 5, toString() {} });
+  assert.strictEqual(
+    inspect(obj, { showHidden: true, colors: true }),
+    '{ \x1B[2mabc: \x1B[33mtrue\x1B[39m\x1B[22m, ' +
+      '\x1B[2mdef: \x1B[33m5\x1B[39m\x1B[22m }'
+  );
 }