From 579e42b3391460725999ef3f96c215e270f8a962 Mon Sep 17 00:00:00 2001
From: MiB-1 <133959537+MiB-1@users.noreply.github.com>
Date: Tue, 18 Nov 2025 09:10:33 +0100
Subject: [PATCH] =?UTF-8?q?fix(LionInputStepper):=20improve=20handling=20o?=
 =?UTF-8?q?f=20decimal=20step=20values=20and=20al=E2=80=A6=20(#2621)?=
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* fix(LionInputStepper): improve handling of decimal step values and alignment

* fix: add changeset LionInputStepper improvements
---
 .changeset/four-rabbits-cover.md              |  5 +++
 .../input-stepper/src/LionInputStepper.js     | 30 ++++++++++----
 .../test/lion-input-stepper.test.js           | 41 +++++++++++++++++++
 3 files changed, 68 insertions(+), 8 deletions(-)
 create mode 100644 .changeset/four-rabbits-cover.md

diff --git a/.changeset/four-rabbits-cover.md b/.changeset/four-rabbits-cover.md
new file mode 100644
index 000000000..a1a0bb20a
--- /dev/null
+++ b/.changeset/four-rabbits-cover.md
@@ -0,0 +1,5 @@
+---
+'@lion/ui': patch
+---
+
+fix(LionInputStepper): improve handling of decimal step values and alignment closes #2615
diff --git a/packages/ui/components/input-stepper/src/LionInputStepper.js b/packages/ui/components/input-stepper/src/LionInputStepper.js
index a04936a38..89f8c7531 100644
--- a/packages/ui/components/input-stepper/src/LionInputStepper.js
+++ b/packages/ui/components/input-stepper/src/LionInputStepper.js
@@ -267,12 +267,19 @@ export class LionInputStepper extends LocalizeMixin(LionInput) {
   _increment() {
     const { step, min, max } = this.values;
     const stepMin = min !== Infinity ? min : 0;
+    const epsilon = 1e-10; // Tolerance for floating-point comparison
 
-    let newValue = this.currentValue + step;
+    let newValue;
 
-    if ((this.currentValue + stepMin) % step !== 0) {
-      // If the value is not aligned to step, align it to the nearest step
-      newValue = Math.floor(this.currentValue / step) * step + step + (stepMin % step);
+    const remainder = (this.currentValue - stepMin) % step;
+    const isAligned = Math.abs(remainder) < epsilon || Math.abs(remainder - step) < epsilon;
+
+    if (!isAligned) {
+      // If the value is not aligned to step, align it to the next valid step
+      newValue = Math.ceil((this.currentValue - stepMin) / step) * step + stepMin;
+    } else {
+      // If the value is aligned, just add the step
+      newValue = this.currentValue + step;
     }
 
     if (newValue <= max || max === Infinity) {
@@ -289,12 +296,19 @@ export class LionInputStepper extends LocalizeMixin(LionInput) {
   _decrement() {
     const { step, max, min } = this.values;
     const stepMin = min !== Infinity ? min : 0;
+    const epsilon = 1e-10; // Tolerance for floating-point comparison
 
-    let newValue = this.currentValue - step;
+    let newValue;
 
-    if ((this.currentValue + stepMin) % step !== 0) {
-      // If the value is not aligned to step, align it to the nearest step
-      newValue = Math.floor(this.currentValue / step) * step + (stepMin % step);
+    const remainder = (this.currentValue - stepMin) % step;
+    const isAligned = Math.abs(remainder) < epsilon || Math.abs(remainder - step) < epsilon;
+
+    if (!isAligned) {
+      // If the value is not aligned to step, align it to the previous valid step
+      newValue = Math.floor((this.currentValue - stepMin) / step) * step + stepMin;
+    } else {
+      // If the value is aligned, just subtract the step
+      newValue = this.currentValue - step;
     }
 
     if (newValue >= min || min === Infinity) {
diff --git a/packages/ui/components/input-stepper/test/lion-input-stepper.test.js b/packages/ui/components/input-stepper/test/lion-input-stepper.test.js
index 5479d8350..17ba2509d 100644
--- a/packages/ui/components/input-stepper/test/lion-input-stepper.test.js
+++ b/packages/ui/components/input-stepper/test/lion-input-stepper.test.js
@@ -359,6 +359,47 @@ describe('<lion-input-stepper>', () => {
         await el.updateComplete;
         expect(el.modelValue).to.equal(-13, 'Fail - : (-23 > 100 by 10; val 55)'); // -23 > -13 > -3 > 7
       });
+
+      it('handles decimal step values correctly', async () => {
+        // Test with decimal step 0.1
+        let el = await fixture(
+          html`<lion-input-stepper step="0.1" min="0" max="9" value="5.55"></lion-input-stepper>`,
+        );
+
+        // Test increment with decimal step
+        let incrementButton = el.querySelector('[slot=suffix]');
+        incrementButton?.dispatchEvent(new Event('click'));
+        await el.updateComplete;
+        expect(el.modelValue).to.equal(5.6, 'Fail + : (0 > 9 by 0.1; val 5.55)');
+
+        // Test decrement with decimal step
+        let decrementButton = el.querySelector('[slot=prefix]');
+        decrementButton?.dispatchEvent(new Event('click'));
+        await el.updateComplete;
+        expect(el.modelValue).to.equal(5.5, 'Fail - : (0 > 9 by 0.1; val 5.6)');
+
+        // Test with value that needs alignment
+        el = await fixture(
+          html`<lion-input-stepper step="0.1" min="0" max="9" value="3.27"></lion-input-stepper>`,
+        );
+
+        // Should align to next step when incrementing
+        incrementButton = el.querySelector('[slot=suffix]');
+        incrementButton?.dispatchEvent(new Event('click'));
+        await el.updateComplete;
+        expect(el.modelValue).to.equal(3.3, 'Fail + alignment: (0 > 9 by 0.1; val 3.27)');
+
+        // Reset and test decrement alignment
+        el = await fixture(
+          html`<lion-input-stepper step="0.1" min="0" max="9" value="3.27"></lion-input-stepper>`,
+        );
+
+        // Should align to previous step when decrementing
+        decrementButton = el.querySelector('[slot=prefix]');
+        decrementButton?.dispatchEvent(new Event('click'));
+        await el.updateComplete;
+        expect(el.modelValue).to.equal(3.2, 'Fail - alignment: (0 > 9 by 0.1; val 3.27)');
+      });
     });
   });