console: make .assert standard compliant

The standard does not throw and has no stack trace.
See https://console.spec.whatwg.org/#assert

PR-URL: https://github.com/nodejs/node/pull/17706
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/console.md

@@ -103,70 +103,33 @@ The global `console` is a special `Console` whose output is sent to
 new Console(process.stdout, process.stderr);
 ```
 
-### console.assert(value[, message][, ...args])
+### console.assert(value[, ...message])
 <!-- YAML
 added: v0.1.101
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/REPLACEME
+    description: The implementation is now spec compliant and does not throw
+                 anymore.
 -->
-* `value` {any}
+* `value` {any} The value tested for being truthy.
-* `message` {any}
+* `...message` {any} All arguments besides `value` are used as error message.
-* `...args` {any}
 
 A simple assertion test that verifies whether `value` is truthy. If it is not,
-an `AssertionError` is thrown. If provided, the error `message` is formatted
+`Assertion failed` is logged. If provided, the error `message` is formatted
-using [`util.format()`][] and used as the error message.
+using [`util.format()`][] by passing along all message arguments. The output is
+used as the error message.
 
 ```js
 console.assert(true, 'does nothing');
 // OK
-console.assert(false, 'Whoops %s', 'didn\'t work');
+console.assert(false, 'Whoops %s work', 'didn\'t');
-// AssertionError: Whoops didn't work
+// Assertion failed: Whoops didn't work
 ```
 
-*Note*: The `console.assert()` method is implemented differently in Node.js
+*Note*: Calling `console.assert()` with a falsy assertion will only cause the
-than the `console.assert()` method [available in browsers][web-api-assert].
+`message` to be printed to the console without interrupting execution of
-
+subsequent code.
-Specifically, in browsers, calling `console.assert()` with a falsy
-assertion will cause the `message` to be printed to the console without
-interrupting execution of subsequent code. In Node.js, however, a falsy
-assertion will cause an `AssertionError` to be thrown.
-
-Functionality approximating that implemented by browsers can be implemented
-by extending Node.js' `console` and overriding the `console.assert()` method.
-
-In the following example, a simple module is created that extends and overrides
-the default behavior of `console` in Node.js.
-
-<!-- eslint-disable func-name-matching -->
-```js
-'use strict';
-
-// Creates a simple extension of console with a
-// new impl for assert without monkey-patching.
-const myConsole = Object.create(console, {
-  assert: {
-    value: function assert(assertion, message, ...args) {
-      try {
-        console.assert(assertion, message, ...args);
-      } catch (err) {
-        console.error(err.stack);
-      }
-    },
-    configurable: true,
-    enumerable: true,
-    writable: true,
-  },
-});
-
-module.exports = myConsole;
-```
-
-This can then be used as a direct replacement for the built in console:
-
-```js
-const console = require('./myConsole');
-console.assert(false, 'this message will print, but no error thrown');
-console.log('this will also print');
-```
 
 ### console.clear()
 <!-- YAML
@@ -531,4 +494,3 @@ This method does not display anything unless used in the inspector. The
 [customizing `util.inspect()` colors]: util.html#util_customizing_util_inspect_colors
 [inspector]: debugger.html
 [note on process I/O]: process.html#process_a_note_on_process_i_o
-[web-api-assert]: https://developer.mozilla.org/en-US/docs/Web/API/console/assert

lib/console.js

@@ -194,7 +194,8 @@ Console.prototype.trace = function trace(...args) {
 
 Console.prototype.assert = function assert(expression, ...args) {
   if (!expression) {
-    require('assert').ok(false, util.format.apply(null, args));
+    args[0] = `Assertion failed${args.length === 0 ? '' : `: ${args[0]}`}`;
+    this.warn(util.format.apply(null, args));
   }
 };
 

test/parallel/test-console.js

@@ -140,6 +140,16 @@ console.timeEnd();
 console.time(NaN);
 console.timeEnd(NaN);
 
+assert.doesNotThrow(() => {
+  console.assert(false, '%s should', 'console.assert', 'not throw');
+  assert.strictEqual(errStrings[errStrings.length - 1],
+                     'Assertion failed: console.assert should not throw\n');
+});
+
+assert.doesNotThrow(() => {
+  console.assert(true, 'this should not throw');
+});
+
 assert.strictEqual(strings.length, process.stdout.writeTimes);
 assert.strictEqual(errStrings.length, process.stderr.writeTimes);
 common.restoreStdout();
@@ -200,17 +210,6 @@ assert.ok(/^NaN: \d+\.\d{3}ms$/.test(strings.shift().trim()));
 assert.strictEqual(errStrings.shift().split('\n').shift(),
                    'Trace: This is a {"formatted":"trace"} 10 foo');
 
-common.expectsError(() => {
-  console.assert(false, 'should throw');
-}, {
-  code: 'ERR_ASSERTION',
-  message: /^should throw$/
-});
-
-assert.doesNotThrow(() => {
-  console.assert(true, 'this should not throw');
-});
-
 // hijack stderr to catch `process.emitWarning` which is using
 // `process.nextTick`
 common.hijackStderr(common.mustCall(function(data) {