Remove decimal.js-light dependency (#1309)

.changeset/fast-eagles-change.md

@@ -0,0 +1,5 @@
+---
+'@keystatic/core': patch
+---
+
+Remove unnecessary dependency

packages/keystatic/package.json

@@ -141,7 +141,6 @@
     "@urql/exchange-graphcache": "^7.1.2",
     "@urql/exchange-persisted": "^4.3.0",
     "cookie": "^0.5.0",
-    "decimal.js-light": "^2.5.1",
     "emery": "^1.4.1",
     "escape-string-regexp": "^4.0.0",
     "fast-deep-equal": "^3.1.3",

packages/keystatic/src/form/fields/number/isAtStep.test.ts

@@ -0,0 +1,28 @@
+import { isAtStep } from './validateNumber';
+import { test, expect } from '@jest/globals';
+
+for (const [value, step] of [
+  [5, 1],
+  [5, 0.1],
+  [5, 0.5],
+  [5, 5e-3],
+  [5.1, 0.1],
+  [5.1, 1e-6],
+  [5.1, 1e-7],
+  [5.1, 1e-200],
+  [300, 3e-200],
+]) {
+  test(`value: ${value}, step: ${step} should be true`, () => {
+    expect(isAtStep(value, step)).toBe(true);
+  });
+}
+
+for (const [value, step] of [
+  [5.1, 1],
+  [5.1, 0.5],
+  [5.1, 3e-200],
+]) {
+  test(`value: ${value}, step: ${step} should be false`, () => {
+    expect(isAtStep(value, step)).toBe(false);
+  });
+}

packages/keystatic/src/form/fields/number/validateNumber.tsx

@@ -1,5 +1,3 @@
-import Decimal from 'decimal.js-light';
-
 export function validateNumber(
   validation:
     | {
@@ -31,9 +29,25 @@ export function validateNumber(
     if (
       step !== undefined &&
       validation?.validateStep !== undefined &&
-      new Decimal(value).mod(new Decimal(step)).toNumber() !== 0
+      !isAtStep(value, step)
     ) {
       return `${label} must be a multiple of ${step}`;
     }
   }
 }
+
+function decimalPlaces(value: number) {
+  const stringified = value.toString();
+  const indexOfDecimal = stringified.indexOf('.');
+  if (indexOfDecimal === -1) {
+    const indexOfE = stringified.indexOf('e-');
+    return indexOfE === -1 ? 0 : parseInt(stringified.slice(indexOfE + 2));
+  }
+  return stringified.length - indexOfDecimal - 1;
+}
+
+export function isAtStep(value: number, step: number) {
+  const dc = Math.max(decimalPlaces(step), decimalPlaces(value));
+  const base = Math.pow(10, dc);
+  return (value * base) % (step * base) === 0;
+}