Function has non-object prototype 'null' in instanceof check, when I use node but it is fine in Browser

[jackIsZlg]

Looks like a Node.js bug. Logging an object should never crash. The same works in the browser:

function X () {}
X.prototype = null;
x = {};
x.constructor = X;
console.log(x);

Node.js:

Uncaught TypeError: Function has non-object prototype 'null' in instanceof check
    at Function.[Symbol.hasInstance] (<anonymous>)
    at getConstructorName (internal/util/inspect.js:535:13)
    at formatRaw (internal/util/inspect.js:803:23)
    at formatValue (internal/util/inspect.js:793:10)
    at inspect (internal/util/inspect.js:326:10)
    at formatWithOptionsInternal (internal/util/inspect.js:1994:40)
    at formatWithOptions (internal/util/inspect.js:1878:10)
    at Object.value (internal/console/constructor.js:306:14)
    at Object.log (internal/console/constructor.js:341:61)

Browser:

{constructor: ƒ}

node Verison: v14.14.0

[targos]

@nodejs/util

[samal-rasmussen]

Are there any version of node that are not affected by this bug?

[7kms]

v14.15.0 is also fail

[kaizhu256]

looks like v14-regression. v12 (both linux and win32-platform) works fine

#!/bin/sh
node -e '
console.log(process.platform, process.versions);
function X () {}
X.prototype = null;
x = {};
x.constructor = X;
console.log(x);
'

# stdout
# win32 {
#   node: '12.16.0',
#   v8: '7.8.279.23-node.31',
#   uv: '1.34.0',
#   zlib: '1.2.11',
#   brotli: '1.0.7',
#   ares: '1.15.0',
#   modules: '72',
#   nghttp2: '1.40.0',
#   napi: '5',
#   llhttp: '2.0.4',
#   http_parser: '2.9.3',
#   openssl: '1.1.1d',
#   cldr: '35.1',
#   icu: '64.2',
#   tz: '2019c',
#   unicode: '12.1'
# }
# X { constructor: [Function: X] }

[Trystan-SA]

(On Windows 10 - MSI x64 installer)
Node 14.0.0 Work
Node 14.2.0 Work
Node 14.3.0 Work
Node 14.4.0 Work
Node 14.5.0 Fail
Node 14.15.1 Fail
Node 15.2.1 Fail

So something between 14.4.0 and 14.5.0 probably created this bug.

[ExE-Boss]

@Trystan-SA
The PR that caused the regression is #33449.

[jasonwilliams]

This fails for me on v15.0.1

I get

TypeError: Function has non-object prototype 'null' in instanceof check
    at Function.[Symbol.hasInstance] (<anonymous>)
    at getConstructorName (node:internal/util/inspect:545:13)
    at formatRaw (node:internal/util/inspect:813:23)
    at formatValue (node:internal/util/inspect:803:10)
    at formatProperty (node:internal/util/inspect:1689:11)
    at formatRaw (node:internal/util/inspect:1017:9)
    at formatValue (node:internal/util/inspect:803:10)
    at formatProperty (node:internal/util/inspect:1689:11)
    at formatRaw (node:internal/util/inspect:1017:9)
    at formatValue (node:internal/util/inspect:803:10)
    at formatProperty (node:internal/util/inspect:1689:11)
    at formatArray (node:internal/util/inspect:1519:17)
    at formatRaw (node:internal/util/inspect:1014:14)
    at formatValue (node:internal/util/inspect:803:10)
    at formatProperty (node:internal/util/inspect:1689:11)
    at formatRaw (node:internal/util/inspect:1017:9)
    at formatValue (node:internal/util/inspect:803:10)
    at formatProperty (node:internal/util/inspect:1689:11)
    at formatRaw (node:internal/util/inspect:1017:9)
    at formatValue (node:internal/util/inspect:803:10)
    at Object.inspect (node:internal/util/inspect:336:10)

from hitting https://github.com/karma-runner/karma/blob/master/lib/server.js#L66

[marxangels]

v14.17.0 OK

[npenin]

I found another way to reproduce this one (on node v16.15.1):

var x={}
console.log(x instanceof Proxy)

Can we reopen the bug ?

[bnoordhuis]

@npenin can you open a new issue? It's probably not the same bug.

(for the audit log: removed an OoO auto-reply while I was here)