util: inspect all prototypes

lib/internal/util/inspect.js

@@ -322,7 +322,7 @@ function getEmptyFormatArray() {
   return [];
 }
 
-function getConstructorName(obj) {
+function getConstructorName(obj, ctx) {
   let firstProto;
   while (obj) {
     const descriptor = Object.getOwnPropertyDescriptor(obj, 'constructor');
@@ -341,10 +341,11 @@ function getConstructorName(obj) {
   if (firstProto === null) {
     return null;
   }
-  // TODO(BridgeAR): Improve prototype inspection.
-  // We could use inspect on the prototype itself to improve the output.
 
-  return '';
+  return `<${inspect(firstProto, {
+    ...ctx,
+    customInspect: false
+  })}>`;
 }
 
 function getPrefix(constructor, tag, fallback) {
@@ -503,7 +504,7 @@ function formatValue(ctx, value, recurseTimes) {
   }
 
   if (ctx.stop !== undefined) {
-    const name = getConstructorName(value) || value[Symbol.toStringTag];
+    const name = getConstructorName(value, ctx) || value[Symbol.toStringTag];
     return ctx.stylize(`[${name || 'Object'}]`, 'special');
   }
 
@@ -547,7 +548,7 @@ function formatValue(ctx, value, recurseTimes) {
 function formatRaw(ctx, value, recurseTimes) {
   let keys;
 
-  const constructor = getConstructorName(value);
+  const constructor = getConstructorName(value, ctx);
   let tag = value[Symbol.toStringTag];
   if (typeof tag !== 'string')
     tag = '';

test/parallel/test-util-inspect.js

@@ -1738,19 +1738,34 @@ assert.strictEqual(
   );
 }
 
-// Manipulate the prototype to one that we can not handle.
+// Manipulate the prototype in weird ways.
 {
   let obj = { a: true };
   let value = (function() { return function() {}; })();
   Object.setPrototypeOf(value, null);
   Object.setPrototypeOf(obj, value);
-  assert.strictEqual(util.inspect(obj), '{ a: true }');
+  assert.strictEqual(util.inspect(obj), '<[Function]> { a: true }');
+  assert.strictEqual(
+    util.inspect(obj, { colors: true }),
+    '<\u001b[36m[Function]\u001b[39m> { a: \u001b[33mtrue\u001b[39m }'
+  );
 
   obj = { a: true };
   value = [];
   Object.setPrototypeOf(value, null);
   Object.setPrototypeOf(obj, value);
-  assert.strictEqual(util.inspect(obj), '{ a: true }');
+  assert.strictEqual(
+    util.inspect(obj),
+    '<[Array: null prototype] []> { a: true }'
+  );
+
+  function StorageObject() {}
+  StorageObject.prototype = Object.create(null);
+  assert.strictEqual(
+    util.inspect(new StorageObject()),
+    '<[Object: null prototype] {}> {}'
+  );
+
 }
 
 // Check that the fallback always works.