From b3a7897df92c5aa3619729d796a56544dcf1be77 Mon Sep 17 00:00:00 2001
From: Gyanu Mayank <gyanumayank0@gmail.com>
Date: Fri, 9 Oct 2026 20:22:46 +0530
Subject: [PATCH] Serialize decimals that round to a whole number with a
 fractional digit

serializeDecimal rounds with toFixed(3) and strips trailing zeros, so 1.0001
became "1." and 9.9999 became "10.". RFC 9651 section 4.1.5 requires a 0
after the period when the fractional component is zero, and parseItem rejects
both strings with "Decimal cannot end on a period".
---
 changelog.md             |  8 ++++++++
 src/serializer.ts        |  3 ++-
 test/serializer-tests.js | 10 ++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/changelog.md b/changelog.md
index f15acbc..618a83e 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,6 +1,14 @@
 ChangeLog
 =========
 
+2.1.1 (????-??-??)
+------------------
+
+* Decimals that round to a whole number, such as `1.0001`, now serialize as
+  `1.0` instead of `1.`, which is invalid and was rejected by the parser.
+  (@gyanu2507)
+
+
 2.1.0 (2026-09-11)
 ------------------
 
diff --git a/src/serializer.ts b/src/serializer.ts
index 27e81d3..0c75f12 100644
--- a/src/serializer.ts
+++ b/src/serializer.ts
@@ -129,7 +129,8 @@ export function serializeDecimal(input: number): string {
   if (signifantDigits > 12) {
     throw new SerializeError('Fractional numbers are not allowed to have more than 12 significant digits before the decimal point');
   }
-  return out;
+  // A decimal must have at least one fractional digit.
+  return out.endsWith('.') ? out + '0' : out;
 }
 
 export function serializeString(input: string): string {
diff --git a/test/serializer-tests.js b/test/serializer-tests.js
index 6991d9a..54894e9 100644
--- a/test/serializer-tests.js
+++ b/test/serializer-tests.js
@@ -101,6 +101,16 @@ describe('serializer shorthands', () => {
 
   describe('serializeItem', () => {
 
+    it('should keep a fractional digit when a decimal rounds to a whole number', () => {
+
+      for (const [input, expected] of [[1.0001, '1.0'], [9.9999, '10.0'], [-0.0001, '-0.0']]) {
+        const str = serializeItem(input);
+        assert.equal(str, expected);
+        assert.deepEqual(parseItem(str), [Number(expected), new Map()]);
+      }
+
+    });
+
     it('should error when passing a type that\'s not recognized', () => {
 
       let caught = false;