From 150ab4ace77e8609bd32de37c280a68609d54cfb Mon Sep 17 00:00:00 2001
From: kevin <5299031+kevin9327@users.noreply.github.com>
Date: Fri, 30 Oct 2026 21:33:18 +0900
Subject: [PATCH] [babel-plugin] Keep the unit of an uppercase zero time, angle
 or fr value

---
 .../transform-value-normalization-test.js     | 34 +++++++++++++++++++
 .../utils/normalizers/zero-dimensions.js      | 11 +++---
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/packages/@stylexjs/babel-plugin/__tests__/transform-value-normalization-test.js b/packages/@stylexjs/babel-plugin/__tests__/transform-value-normalization-test.js
index 9ab0eb1d3..9f957a6e8 100644
--- a/packages/@stylexjs/babel-plugin/__tests__/transform-value-normalization-test.js
+++ b/packages/@stylexjs/babel-plugin/__tests__/transform-value-normalization-test.js
@@ -191,6 +191,40 @@ describe('@stylexjs/babel-plugin', () => {
       `);
     });
 
+    test('0 dimensions keep their unit category whatever its case', () => {
+      expect(
+        transform(`
+          import stylex from 'stylex';
+          const styles = stylex.create({
+            x: { transitionDuration: '0MS' },
+            y: { animationDelay: '0S' },
+            z: { transform: '0DEG' },
+            w: { gridTemplateColumns: '0FR 1fr' }
+          });
+        `),
+      ).toMatchInlineSnapshot(`
+        "import _inject from "@stylexjs/stylex/lib/stylex-inject";
+        var _inject2 = _inject;
+        import stylex from 'stylex';
+        _inject2({
+          ltr: ".x1mq3mr6{transition-duration:0s}",
+          priority: 3000
+        });
+        _inject2({
+          ltr: ".x1uzojwf{animation-delay:0s}",
+          priority: 3000
+        });
+        _inject2({
+          ltr: ".x1jpfit1{transform:0deg}",
+          priority: 3000
+        });
+        _inject2({
+          ltr: ".xkxvfks{grid-template-columns:0fr 1fr}",
+          priority: 3000
+        });"
+      `);
+    });
+
     test('calc() preserves spaces around "+" and "-"', () => {
       expect(
         transform(`
diff --git a/packages/@stylexjs/babel-plugin/src/shared/utils/normalizers/zero-dimensions.js b/packages/@stylexjs/babel-plugin/src/shared/utils/normalizers/zero-dimensions.js
index 639c7ad5d..ab45a383a 100644
--- a/packages/@stylexjs/babel-plugin/src/shared/utils/normalizers/zero-dimensions.js
+++ b/packages/@stylexjs/babel-plugin/src/shared/utils/normalizers/zero-dimensions.js
@@ -48,13 +48,16 @@ export default function normalizeZeroDimensions(
     if (!dimension || dimension.number !== '0') {
       return;
     }
-    if (angles.indexOf(dimension.unit) !== -1) {
+    // CSS units are ASCII case-insensitive: `0MS` is a time and `0FR` a flex
+    // value, and dropping their unit would change what the value means.
+    const unit = dimension.unit.toLowerCase();
+    if (angles.indexOf(unit) !== -1) {
       node.value = '0deg';
-    } else if (timings.indexOf(dimension.unit) !== -1) {
+    } else if (timings.indexOf(unit) !== -1) {
       node.value = '0s';
-    } else if (dimension.unit === fraction) {
+    } else if (unit === fraction) {
       node.value = '0fr';
-    } else if (dimension.unit === percentage) {
+    } else if (unit === percentage) {
       node.value = '0%';
     } else if (!endFunction) {
       node.value = '0';