fix!: use spec Error.cause property instead of legacy cause() function

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [18, 20, 22]
+        node-version: [24, 26]
     steps:
       - name: Checkout
         uses: actions/checkout@v7
@@ -21,22 +21,3 @@ jobs:
         run: npm ci
       - name: Test / Lint / Codestyle
         run: make all
-  test-optional:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        node-version: [24]
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v7
-      - name: Setup Node.js
-        uses: actions/setup-node@v7
-        with:
-          node-version: ${{ matrix.node-version }}
-      - name: Install
-        run: npm ci
-        continue-on-error: true
-      - name: Test / Lint / Codestyle
-        run: make all
-        continue-on-error: true

CHANGES.md

@@ -1,5 +1,12 @@
 # Change log
 
+## 9.0.0-rc.0
+
+- BREAKING: upgrade to `@netflix/nerror@2.0.0-rc.0`, which drops the legacy
+  `.cause()` function in favor of the spec `Error.prototype.cause` property.
+  `lib/serializer.js` and `lib/baseClasses/HttpError.js` now read `err.cause`
+  as a property instead of invoking it as a function.
+
 ## 7.0.0
 
 - BREAKING: omit node domains from serializer

lib/baseClasses/HttpError.js

@@ -149,8 +149,8 @@ HttpError.prototype.toJSON = function toJSON() {
     var message = '';
 
     // if we have a cause, get the full VError toString() without the current
-    // error name. verbose check, self.cause can exist but returns undefined
-    if (self.cause && typeof self.cause === 'function' && self.cause()) {
+    // error name.
+    if (self.cause) {
         var fullString = self.toString();
         message = fullString.substr(fullString.indexOf(' ') + 1);
     } else {
@@ -159,8 +159,7 @@ HttpError.prototype.toJSON = function toJSON() {
 
     return {
         code: self.body.code,
-        message: message,
-        cause: self.cause
+        message: message
     };
 };
 

lib/serializer.js

@@ -71,7 +71,7 @@ function _getMultiErrorStack(err) {
 
 
 /**
- * loop through all cause() errors and build a stack trace output
+ * loop through all cause errors and build a stack trace output
  * @private
  * @method _getFullErrorStack
  * @param {Object} err an error object
@@ -94,7 +94,7 @@ function _getFullErrorStack(err) {
 
         out += stackString.shift() + self._getSerializedContext(e);
         out += stackString.join('\n');
-        e = (typeof e.cause === 'function') ? e.cause() : null;
+        e = e.cause || null;
         first = false;
     } while (e);