From 7c7f86c2e712697daa1c55cb1c2628699f0fda30 Mon Sep 17 00:00:00 2001
From: Gil Pedersen <git@gpost.dk>
Date: Thu, 7 Dec 2023 11:36:27 +0100
Subject: [PATCH] Assign .cause if not handled by super() call

---
 lib/index.js  |  4 ++++
 test/index.js | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/index.js b/lib/index.js
index 22a4925..314f7c2 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -85,6 +85,10 @@ exports.Boom = class Boom extends Error {
         super(message ?? internals.codes.get(statusCode) ?? 'Unknown', { cause });
         Error.captureStackTrace(this, ctor);                           // Filter the stack to our external API
 
+        if (cause !== undefined) {
+            this.cause ??= cause;                                      // Explicitly assign cause to work with old runtimes
+        }
+
         internals.apply(this, data, statusCode, headers);
     }
 
diff --git a/test/index.js b/test/index.js
index e122020..dd63d65 100755
--- a/test/index.js
+++ b/test/index.js
@@ -122,6 +122,27 @@ describe('Boom', () => {
         expect(err.output.payload.error).to.equal('Unknown');
     });
 
+    it('assigns a .cause property if Error does not support it', (flags) => {
+
+        const proto = Object.getPrototypeOf(Boom.Boom);
+        Object.setPrototypeOf(Boom.Boom, class extends Error {
+
+            constructor(message, _options) {
+
+                super(message);
+            }
+        });
+
+        flags.onCleanup = () => {
+
+            Object.setPrototypeOf(Boom.Boom, proto);
+        };
+
+        const err = new Boom.Boom('fail', { cause: 0 });
+        expect(err.cause).to.exist();
+        expect(err.cause).to.equal(0);
+    });
+
     describe('instanceof', () => {
 
         it('identifies a boom object', () => {