fix(web): guard price axis fraction digits

apps/web/src/components/Charts/PriceChart/utils.test.ts

@@ -0,0 +1,45 @@
+import { FiatCurrency } from 'uniswap/src/features/fiatCurrency/constants'
+import type { useLocalizationContext } from 'uniswap/src/features/language/LocalizationContext'
+import { NumberType } from 'utilities/src/format/types'
+import { describe, expect, it, vi } from 'vitest'
+import { formatPriceAxisLabel } from '~/components/Charts/PriceChart/utils'
+
+function createFormat() {
+  return {
+    convertFiatAmount: vi.fn((amount: number) => ({ amount, currency: FiatCurrency.UnitedStatesDollar })),
+    convertFiatAmountFormatted: vi.fn((amount: number, type: NumberType) => `${type}:${amount}`),
+  }
+}
+
+describe('formatPriceAxisLabel', () => {
+  it('formats a valid fixed precision as currency', () => {
+    const format = createFormat()
+
+    expect(
+      formatPriceAxisLabel({
+        scaledPrice: 1.234,
+        scaleFactor: 1,
+        decimals: 2,
+        format: format as unknown as ReturnType<typeof useLocalizationContext>,
+        locale: 'en-US',
+      }),
+    ).toBe('$1.23')
+    expect(format.convertFiatAmountFormatted).not.toHaveBeenCalled()
+  })
+
+  it('falls back when precision exceeds Intl.NumberFormat limits', () => {
+    const format = createFormat()
+
+    expect(
+      formatPriceAxisLabel({
+        scaledPrice: 1.234,
+        scaleFactor: 1,
+        decimals: 101,
+        format: format as unknown as ReturnType<typeof useLocalizationContext>,
+        locale: 'en-US',
+      }),
+    ).toBe(`fiat-token-price:1.234`)
+    expect(format.convertFiatAmount).not.toHaveBeenCalled()
+    expect(format.convertFiatAmountFormatted).toHaveBeenCalledWith(1.234, NumberType.FiatTokenPrice)
+  })
+})

apps/web/src/components/Charts/PriceChart/utils.ts

@@ -4,6 +4,12 @@ import { useLocalizationContext } from 'uniswap/src/features/language/Localizati
 import { NumberType } from 'utilities/src/format/types'
 import { PricePoint } from '~/data/util'
 
+const MAX_INTL_FRACTION_DIGITS = 100
+
+function isValidFractionDigits(decimals: number): boolean {
+  return Number.isInteger(decimals) && decimals >= 0 && decimals <= MAX_INTL_FRACTION_DIGITS
+}
+
 /**
  * Returns the minimum and maximum values in the given array of PricePoints.
  */
@@ -80,7 +86,7 @@ export function formatPriceAxisLabel({
   if (tokenFormatType) {
     return format.formatNumberOrString({ value: price, type: tokenFormatType })
   }
-  if (decimals !== undefined) {
+  if (decimals !== undefined && isValidFractionDigits(decimals)) {
     const { amount, currency } = format.convertFiatAmount(price)
     return new Intl.NumberFormat(locale, {
       style: 'currency',