From ade5de0ca5bd15c974cdca329051284cf0a1a022 Mon Sep 17 00:00:00 2001
From: Oskar Eichler <oskar@songstats.com>
Date: Sun, 30 Aug 2026 00:12:46 +0200
Subject: [PATCH] Handle empty by-function inputs

---
 lib/jmespath/nodes/function.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/jmespath/nodes/function.rb b/lib/jmespath/nodes/function.rb
index 9d23e41..88c937c 100644
--- a/lib/jmespath/nodes/function.rb
+++ b/lib/jmespath/nodes/function.rb
@@ -474,8 +474,10 @@ def call(args)
           if get_type(args[0]) == ARRAY_TYPE && get_type(args[1]) == EXPRESSION_TYPE
             values = args[0].to_ary
             expression = args[1]
+            return [] if values.empty?
+
             array_type = get_type(expression.eval(values[0]))
-            if array_type == STRING_TYPE || array_type == NUMBER_TYPE || values.empty?
+            if array_type == STRING_TYPE || array_type == NUMBER_TYPE
               # stable sort the list
               n = 0
               values.sort_by do |value|
@@ -509,6 +511,8 @@ def compare_by(mode, *args)
           expression = args[1]
           if get_type(values) == ARRAY_TYPE && get_type(expression) == EXPRESSION_TYPE
             values = values.to_ary
+            return nil if values.empty?
+
             type = get_type(expression.eval(values.first))
             if type != NUMBER_TYPE && type != STRING_TYPE
               msg = "function #{mode}() expects values to be strings or numbers"