From 022cb142d703c06efdbe0ae5a7b3ec47cc623d0e Mon Sep 17 00:00:00 2001
From: Yarchik <spoko.dev@gmail.com>
Date: Wed, 24 Jun 2026 01:44:35 +0100
Subject: [PATCH] fix: return null for avg() of empty array

avg() over an empty array returned NaN (0/0) instead of null. The JMESPath spec states an empty array produces a return value of null. Guard the empty case before the sum loop and add the compliance case avg(empty_list) = null.
---
 jmespath.js                    | 3 +++
 test/compliance/functions.json | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/jmespath.js b/jmespath.js
index 0a36691..deaf4a2 100644
--- a/jmespath.js
+++ b/jmespath.js
@@ -1358,6 +1358,9 @@
     _functionAvg: function(resolvedArgs) {
         var sum = 0;
         var inputArray = resolvedArgs[0];
+        if (inputArray.length === 0) {
+            return null;
+        }
         for (var i = 0; i < inputArray.length; i++) {
             sum += inputArray[i];
         }
diff --git a/test/compliance/functions.json b/test/compliance/functions.json
index 8b8db36..a749dda 100644
--- a/test/compliance/functions.json
+++ b/test/compliance/functions.json
@@ -83,6 +83,10 @@
       "expression": "avg(strings)",
       "error": "invalid-type"
     },
+    {
+      "expression": "avg(empty_list)",
+      "result": null
+    },
     {
       "expression": "ceil(`1.2`)",
       "result": 2