Fix inconsistent number formatting between mobile and web (#6384)

* Manual truncation & identify factor points for each lang

* Reduce indirection

* Add test

Co-authored-by: khuddite <biliie811028@hotmail.com>

* Handle big numbers, clarify special case

* Clarify the reason

---------

Co-authored-by: Dan Abramov <dan.abramov@gmail.com>

1 files changed, 92 insertions, 0 deletions

diff --git a/src/view/com/util/numeric/__tests__/format-test.ts b/src/view/com/util/numeric/__tests__/format-test.ts
new file mode 100644
index 000000000..74df4be4c
--- /dev/null
+++ b/src/view/com/util/numeric/__tests__/format-test.ts
@@ -0,0 +1,92 @@
+import {describe, expect, it} from '@jest/globals'
+
+import {APP_LANGUAGES} from '#/locale/languages'
+import {formatCount} from '../format'
+
+const formatCountRound = (locale: string, num: number) => {
+  const options: Intl.NumberFormatOptions = {
+    notation: 'compact',
+    maximumFractionDigits: 1,
+  }
+  return new Intl.NumberFormat(locale, options).format(num)
+}
+
+const formatCountTrunc = (locale: string, num: number) => {
+  const options: Intl.NumberFormatOptions = {
+    notation: 'compact',
+    maximumFractionDigits: 1,
+    // @ts-ignore
+    roundingMode: 'trunc',
+  }
+  return new Intl.NumberFormat(locale, options).format(num)
+}
+
+// prettier-ignore
+const testNums = [
+  1,
+  5,
+  9,
+  11,
+  55,
+  99,
+  111,
+  555,
+  999,
+  1111,
+  5555,
+  9999,
+  11111,
+  55555,
+  99999,
+  111111,
+  555555,
+  999999,
+  1111111,
+  5555555,
+  9999999,
+  11111111,
+  55555555,
+  99999999,
+  111111111,
+  555555555,
+  999999999,
+  1111111111,
+  5555555555,
+  9999999999,
+  11111111111,
+  55555555555,
+  99999999999,
+  111111111111,
+  555555555555,
+  999999999999,
+  1111111111111,
+  5555555555555,
+  9999999999999,
+  11111111111111,
+  55555555555555,
+  99999999999999,
+  111111111111111,
+  555555555555555,
+  999999999999999,
+  1111111111111111,
+  5555555555555555,
+]
+
+describe('formatCount', () => {
+  for (const appLanguage of APP_LANGUAGES) {
+    const locale = appLanguage.code2
+    it('truncates for ' + locale, () => {
+      const mockI8nn = {
+        locale,
+        number(num: number) {
+          return formatCountRound(locale, num)
+        },
+      }
+      for (const num of testNums) {
+        const formatManual = formatCount(mockI8nn as any, num)
+        const formatOriginal = formatCountTrunc(locale, num)
+        expect(formatManual).toEqual(formatOriginal)
+      }
+    })
+  }
+})