fix(kit): InputNumber has rounding problems on blur with float large numbers

.cspell.json

@@ -3,7 +3,7 @@
     "import": ["@taiga-ui/cspell-config/cspell.config.js"],
     "files": ["*/*.*"],
     "ignorePaths": ["**/projects/i18n/languages/**", "**/addon-commerce/utils/get-currency-symbol.ts"],
-    "ignoreWords": ["Wachovia", "bottomsheet", "appbar", "qwertypgj_", "antialiasing", "xxxs"],
+    "ignoreWords": ["Wachovia", "bottomsheet", "appbar", "qwertypgj_", "antialiasing", "xxxs", "significand"],
     "ignoreRegExpList": ["\\(https?://.*?\\)", "\\/{1}.+\\/{1}", "\\%2F.+", "\\%2C.+", "\\ɵ.+", "\\ыва.+"],
     "overrides": [
         {

projects/cdk/utils/math/round.ts

@@ -18,14 +18,24 @@
         return value;
     }
 
     ngDevMode && console.assert(!Number.isNaN(value), 'Value must be number');
     ngDevMode && console.assert(Number.isInteger(precision), 'Precision must be integer');
 
     precision = Math.min(precision, MAX_PRECISION);
 
-    const pair = `${value}e`.split('e');
-    const tempValue = func(Number(`${pair[0]}e${Number(pair[1]) + precision}`));
-    const processedPair = `${tempValue}e`.split('e');
+    const [significand, exponent = ''] = `${value}`.split('e');
+    const roundedInt = func(Number(`${significand}e${Number(exponent) + precision}`));
+
+    /**
+     * TODO: use BigInt after bumping Safari to 14+
+     */
+    ngDevMode &&
+        console.assert(
+            Number.isSafeInteger(roundedInt),
+            'Impossible to correctly round the such large number',
+        );
+
+    const processedPair = `${roundedInt}e`.split('e');
 
     return Number(`${processedPair[0]}e${Number(processedPair[1]) - precision}`);
 }
@@ -45,3 +55,7 @@
 export function tuiTrunc(value: number, precision = 0): number {
     return calculate(value, precision, Math.trunc);
 }
+
+export function tuiIsSafeToRound(value: number, precision = 0): boolean {
+    return Number.isSafeInteger(Math.trunc(value * 10 ** precision));
+}

projects/core/utils/format/test/format-number.spec.ts

@@ -140,4 +140,14 @@ describe('Number formatting', () => {
             }),
         ).toBe('0');
     });
+
+    it('does not mutate value if precision is infinite', () => {
+        expect(
+            tuiFormatNumber(123_456_789_012_345.67, {
+                precision: Infinity,
+                thousandSeparator: ',',
+                rounding: 'round',
+            }),
+        ).toBe('123,456,789,012,345.67');
+    });
 });

projects/demo-playwright/tests/legacy/input-number/input-number.pw.spec.ts

@@ -29,6 +29,22 @@
             await expect(example).toHaveScreenshot('01-input-number.png');
         });
 
+        test('does not mutate already valid too large number on blur', async ({page}) => {
+            await tuiGoto(
+                page,
+                `${DemoRoute.InputNumber}/API?thousandSeparator=_&precision=2`,
+            );
+            await input.focus();
+            await input.clear();
+            await input.pressSequentially('123456789012345.6789');
+
+            await expect(input).toHaveValue('123_456_789_012_345.67');
+
+            await input.blur();
+
+            await expect(input).toHaveValue('123_456_789_012_345.67');
+        });
+
         test('prefix + value + postfix', async ({page}) => {
             await tuiGoto(
                 page,

projects/legacy/components/input-number/input-number.component.ts

@@ -19,7 +19,7 @@ import type {TuiValueTransformer} from '@taiga-ui/cdk/classes';
 import {CHAR_HYPHEN, CHAR_MINUS, EMPTY_QUERY} from '@taiga-ui/cdk/constants';
 import {tuiWatch} from '@taiga-ui/cdk/observables';
 import {TUI_IS_IOS} from '@taiga-ui/cdk/tokens';
-import {tuiClamp} from '@taiga-ui/cdk/utils/math';
+import {tuiClamp, tuiIsSafeToRound} from '@taiga-ui/cdk/utils/math';
 import {tuiCreateToken, tuiPure} from '@taiga-ui/cdk/utils/miscellaneous';
 import type {TuiDecimalMode} from '@taiga-ui/core/tokens';
 import {TUI_DEFAULT_NUMBER_FORMAT, TUI_NUMBER_FORMAT} from '@taiga-ui/core/tokens';
@@ -274,7 +274,15 @@ export class TuiInputNumberComponent
             this.computedPrefix +
             tuiFormatNumber(value, {
                 ...this.numberFormat,
-                precision: this.precision,
+                /**
+                 * Number can satisfy interval [Number.MIN_SAFE_INTEGER; Number.MAX_SAFE_INTEGER]
+                 * but its rounding can violate it.
+                 * Before BigInt support there is no perfect solution – only trade off.
+                 * No rounding is better than lose precision and incorrect mutation of already valid value.
+                 */
+                precision: tuiIsSafeToRound(value, this.precision)
+                    ? this.precision
+                    : Infinity,
             }).replace(CHAR_HYPHEN, CHAR_MINUS) +
             this.computedPostfix
         );