assert: add default operator to `assert.fail()`

This makes sure `assert.fail()` contains an operator instead of being
undefined.

On top of that it also fixes the `err.generatedMessage` property.
Before, it was not always set correct.

PR-URL: https://github.com/nodejs/node/pull/22694
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 16 insertions, 5 deletions

diff --git a/lib/assert.js b/lib/assert.js
index e336119d92..0f3d770358 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -87,8 +87,9 @@ function innerFail(obj) {
 function fail(actual, expected, message, operator, stackStartFn) {
   const argsLen = arguments.length;
 
+  let internalMessage;
   if (argsLen === 0) {
-    message = 'Failed';
+    internalMessage = 'Failed';
   } else if (argsLen === 1) {
     message = actual;
     actual = undefined;
@@ -106,13 +107,23 @@ function fail(actual, expected, message, operator, stackStartFn) {
       operator = '!=';
   }
 
-  innerFail({
+  if (message instanceof Error) throw message;
+
+  const errArgs = {
     actual,
     expected,
-    message,
-    operator,
+    operator: operator === undefined ? 'fail' : operator,
     stackStartFn: stackStartFn || fail
-  });
+  };
+  if (message !== undefined) {
+    errArgs.message = message;
+  }
+  const err = new AssertionError(errArgs);
+  if (internalMessage) {
+    err.message = internalMessage;
+    err.generatedMessage = true;
+  }
+  throw err;
 }
 
 assert.fail = fail;