From e9cbe9517be2d8e2f55882f187544bdc4e232170 Mon Sep 17 00:00:00 2001
From: Marcus Elg <marcusaccounts@yahoo.se>
Date: Thu, 25 Aug 2022 07:47:03 +0200
Subject: [PATCH] Improve %f formatting for inf and nan

---
 core/ustring.cpp           | 7 +++++--
 main/tests/test_string.cpp | 8 ++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/core/ustring.cpp b/core/ustring.cpp
index 0c528e88942..2be12d25b12 100644
--- a/core/ustring.cpp
+++ b/core/ustring.cpp
@@ -4339,15 +4339,18 @@ String String::sprintf(const Array &values, bool *error) const {
 					double value = values[value_index];
 					bool is_negative = (value < 0);
 					String str = String::num(ABS(value), min_decimals);
+					bool not_numeric = isinf(value) || isnan(value);
 
 					// Pad decimals out.
-					str = str.pad_decimals(min_decimals);
+					if (!not_numeric) {
+						str = str.pad_decimals(min_decimals);
+					}
 
 					int initial_len = str.length();
 
 					// Padding. Leave room for sign later if required.
 					int pad_chars_count = (is_negative || show_sign) ? min_chars - 1 : min_chars;
-					String pad_char = pad_with_zeros ? String("0") : String(" ");
+					String pad_char = (pad_with_zeros && !not_numeric) ? String("0") : String(" "); // Never pad NaN or inf with zeros
 					if (left_justified) {
 						str = str.rpad(pad_chars_count, pad_char);
 					} else {
diff --git a/main/tests/test_string.cpp b/main/tests/test_string.cpp
index 4115bb2433e..162b677bc9d 100644
--- a/main/tests/test_string.cpp
+++ b/main/tests/test_string.cpp
@@ -638,6 +638,14 @@ bool test_28() {
 	OS::get_singleton()->print(output_format, format.c_str(), output.c_str(), success ? "OK" : "FAIL");
 	state = state && success;
 
+	// Real (infinity) left-padded
+	format = "fish %11f frog";
+	args.clear();
+	args.push_back(INFINITY);
+	output = format.sprintf(args, &error);
+	success = (output == String("fish         inf frog") && !error);
+	state = state && success;
+
 	// Real right-padded
 	format = "fish %-11f frog";
 	args.clear();