From 11e454c0fdd2da8cc6b5821b89c03c52a7c64b91 Mon Sep 17 00:00:00 2001
From: Isaac Cambron <icambron@gmail.com>
Date: Tue, 22 Aug 2023 16:28:17 -0400
Subject: [PATCH] Fix for negative units in conversions

Closes #1482
---
 src/duration.js             | 7 ++++---
 src/impl/util.js            | 4 ++++
 test/duration/units.test.js | 9 +++++++++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/duration.js b/src/duration.js
index 56cf194b1..76a57b276 100644
--- a/src/duration.js
+++ b/src/duration.js
@@ -10,6 +10,7 @@ import {
   isUndefined,
   normalizeObject,
   roundTo,
+  signedFloor,
 } from "./impl/util.js";
 import Settings from "./settings.js";
 import DateTime from "./datetime.js";
@@ -133,9 +134,9 @@ function removePrecisionIssue(a) {
 
 // NB: mutates parameters
 function convert(matrix, fromMap, fromUnit, toMap, toUnit) {
-  const conv = matrix[toUnit][fromUnit],
-    raw = fromMap[fromUnit] / conv,
-    added = Math.floor(raw);
+  const conv = matrix[toUnit][fromUnit];
+  const raw = fromMap[fromUnit] / conv;
+  const added = signedFloor(raw);
 
   toMap[toUnit] = removePrecisionIssue(toMap[toUnit] + added);
   fromMap[fromUnit] = removePrecisionIssue(fromMap[fromUnit] - added * conv);
diff --git a/src/impl/util.js b/src/impl/util.js
index 51f756ea4..b934b1053 100644
--- a/src/impl/util.js
+++ b/src/impl/util.js
@@ -124,6 +124,10 @@ export function parseMillis(fraction) {
   }
 }
 
+export function signedFloor(number) {
+  return number > 0 ? Math.floor(number) : Math.ceil(number);
+}
+
 export function roundTo(number, digits, towardZero = false) {
   const factor = 10 ** digits,
     rounder = towardZero ? Math.trunc : Math.round;
diff --git a/test/duration/units.test.js b/test/duration/units.test.js
index 2b37fad4f..42aaf2397 100644
--- a/test/duration/units.test.js
+++ b/test/duration/units.test.js
@@ -96,6 +96,15 @@ test("Duration#shiftTo boils hours down to hours and minutes", () => {
   });
 });
 
+test("Duration#shiftTo handles mixed units", () => {
+  const dur = Duration.fromObject({ weeks: -1, days: 14 });
+  expect(dur.shiftTo("years", "months", "weeks").toObject()).toEqual({
+    years: 0,
+    months: 0,
+    weeks: 1,
+  });
+});
+
 //------
 // #shiftToAll()
 //-------