util: improve function inspection

This commit contains the following changes:

1) Add null prototype support for functions.
2) Safely detect async and generator functions.
3) Mark anonymous functions as such instead of just leaving out the
   name.

PR-URL: https://github.com/nodejs/node/pull/27227
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 30 insertions, 7 deletions

diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
index fccb46085d..8ffa303268 100644
--- a/lib/internal/util/inspect.js
+++ b/lib/internal/util/inspect.js
@@ -49,6 +49,8 @@ const {
 } = require('internal/errors');
 
 const {
+  isAsyncFunction,
+  isGeneratorFunction,
   isAnyArrayBuffer,
   isArrayBuffer,
   isArgumentsObject,
@@ -642,14 +644,9 @@ function formatRaw(ctx, value, recurseTimes, typedArray) {
         return `${braces[0]}}`;
       }
     } else if (typeof value === 'function') {
-      const type = constructor || tag || 'Function';
-      let name = `${type}`;
-      if (value.name && typeof value.name === 'string') {
-        name += `: ${value.name}`;
-      }
+      base = getFunctionBase(value, constructor, tag);
       if (keys.length === 0)
-        return ctx.stylize(`[${name}]`, 'special');
-      base = `[${name}]`;
+        return ctx.stylize(base, 'special');
     } else if (isRegExp(value)) {
       // Make RegExps say that they are RegExps
       base = RegExpPrototype.toString(
@@ -834,6 +831,32 @@ function getBoxedBase(value, ctx, keys, constructor, tag) {
   return ctx.stylize(base, type.toLowerCase());
 }
 
+function getFunctionBase(value, constructor, tag) {
+  let type = 'Function';
+  if (isAsyncFunction(value)) {
+    type = 'AsyncFunction';
+  } else if (isGeneratorFunction(value)) {
+    type = 'GeneratorFunction';
+  }
+  let base = `[${type}`;
+  if (constructor === null) {
+    base += ' (null prototype)';
+  }
+  if (value.name === '') {
+    base += ' (anonymous)';
+  } else {
+    base += `: ${value.name}`;
+  }
+  base += ']';
+  if (constructor !== type && constructor !== null) {
+    base += ` ${constructor}`;
+  }
+  if (tag !== '' && constructor !== tag) {
+    base += ` [${tag}]`;
+  }
+  return base;
+}
+
 function formatError(err, constructor, tag, ctx) {
   // TODO(BridgeAR): Always show the error code if present.
   let stack = err.stack || ErrorPrototype.toString(err);