From 3f81ce63d636aa50fcab3604c7cadaafab8af4f3 Mon Sep 17 00:00:00 2001
From: Jonathan Giroux <giroux.jo@gmail.com>
Date: Mon, 13 Jun 2022 13:18:16 +0200
Subject: [PATCH] Fix `evaluateCause` loosing access to `err`

---
 lib/err-helpers.js | 12 ++++++------
 lib/err.js         |  2 +-
 test/err.test.js   | 22 ++++++++++++++++------
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/lib/err-helpers.js b/lib/err-helpers.js
index d00c201..1164a33 100644
--- a/lib/err-helpers.js
+++ b/lib/err-helpers.js
@@ -12,7 +12,7 @@
 const getErrorCause = (err) => {
   if (!err) return
 
-  const cause = evaluateCause(err.cause)
+  const cause = evaluateCause(err)
 
   return cause instanceof Error
     ? cause
@@ -20,14 +20,14 @@ const getErrorCause = (err) => {
 }
 
 /**
- * @param {unknown|(()=>err)} cause
+ * @param {Error|{ cause?: unknown|(()=>err)}} err
  * @returns {Error|undefined}
  */
-const evaluateCause = (cause) => {
+const evaluateCause = (err) => {
   // VError / NError style causes are functions
-  return typeof cause === 'function'
-    ? cause()
-    : cause
+  return typeof err.cause === 'function'
+    ? err.cause()
+    : err.cause
 }
 
 /**
diff --git a/lib/err.js b/lib/err.js
index fd63e23..665bba2 100644
--- a/lib/err.js
+++ b/lib/err.js
@@ -66,7 +66,7 @@ function errSerializer (err) {
   }
 
   if (err.cause) {
-    const cause = evaluateCause(err.cause)
+    const cause = evaluateCause(err)
     _err.cause = errSerializer(cause)
   }
 
diff --git a/test/err.test.js b/test/err.test.js
index 0ca4a58..7b5bb0a 100644
--- a/test/err.test.js
+++ b/test/err.test.js
@@ -223,16 +223,26 @@ test('serializes causes with VError support', function (t) {
   t.plan(11)
 
   // Fake VError-style setup
-  const err = Error('foo: bar')
-  err.cause = () => {
-    const err = Error('bar')
-    err.cause = Error('abc')
-    return err
+  class VError extends Error {
+    constructor (message, cause) {
+      super(message + ': ' + cause.message)
+      this._cause = cause
+    }
+
+    // Ensure `cause` references `this` (see https://github.com/pinojs/pino-std-serializers/pull/109)
+    cause () {
+      return this._cause
+    }
   }
 
+  const causeErr = Error('bar')
+  causeErr.cause = Error('abc')
+
+  const err = new VError('foo', causeErr)
+
   const serialized = serializer(err)
 
-  t.equal(serialized.type, 'Error')
+  t.equal(serialized.type, 'VError')
   t.equal(serialized.message, 'foo: bar: abc') // message serialization already walks cause-chain
   t.match(serialized.stack, /err\.test\.js:/)