assert: stricter ifError

This makes `assert.ifError` stricter by only accepting `null` and
`undefined` from now on. Before any truthy value was accepted.

Author: BridgeAR

doc/api/assert.md

@@ -438,21 +438,23 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/18247
     description: Instead of throwing the original error it is now wrapped into
                  a AssertionError that contains the full stack trace.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/18247
+    description: Value may now only be `undefined` or `null`. Before any truthy
+                 input was accepted.
 -->
 * `value` {any}
 
-Throws `value` if `value` is truthy. This is useful when testing the `error`
-argument in callbacks.
+Throws `value` if `value` is not `undefined` or `null`. This is useful when
+testing the `error` argument in callbacks.
 
 ```js
 const assert = require('assert').strict;
 
 assert.ifError(null);
 // OK
 assert.ifError(0);
-// OK
-assert.ifError(1);
-// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 1
+// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0
 assert.ifError('error');
 // AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'
 assert.ifError(new Error());

lib/assert.js

@@ -445,7 +445,7 @@ assert.doesNotThrow = function doesNotThrow(block, error, message) {
 };
 
 assert.ifError = function ifError(err) {
-  if (err) {
+  if (err !== null && err !== undefined) {
     let message = 'ifError got unwanted exception: ';
     if (typeof err === 'object' && typeof err.message === 'string') {
       if (err.message.length === 0 && err.constructor) {

test/parallel/test-assert-if-error.js

@@ -60,10 +60,16 @@ assert.throws(
   }
 );
 
+assert.throws(
+  () => { assert.ifError(false); },
+  {
+    message: 'ifError got unwanted exception: false'
+  }
+);
+
 assert.doesNotThrow(() => { assert.ifError(null); });
 assert.doesNotThrow(() => { assert.ifError(); });
 assert.doesNotThrow(() => { assert.ifError(undefined); });
-assert.doesNotThrow(() => { assert.ifError(false); });
 
 // https://github.com/nodejs/node-v0.x-archive/issues/2893
 {

test/sequential/test-inspector-port-zero.js

@@ -16,8 +16,8 @@ function test(arg, port = '') {
   let stderr = '';
   proc.stdout.on('data', (data) => stdout += data);
   proc.stderr.on('data', (data) => stderr += data);
-  proc.stdout.on('close', assert.ifError);
-  proc.stderr.on('close', assert.ifError);
+  proc.stdout.on('close', (hadErr) => assert(!hadErr));
+  proc.stderr.on('close', (hadErr) => assert(!hadErr));
   proc.stderr.on('data', () => {
     if (!stderr.includes('\n')) return;
     assert(/Debugger listening on (.+)/.test(stderr));