[localization] Add default temperature unit to the locale

packages/expo-localization/CHANGELOG.md

@@ -7,6 +7,7 @@
 ### 🎉 New features
 
 - Added support for React Native 0.73. ([#24018](https://github.com/expo/expo/pull/24018) by [@kudo](https://github.com/kudo))
+- Added a `temperatureUnit` field, which contains the default temperature unit for the locale. ([#24059](https://github.com/expo/expo/pull/24059) by [@behenate](https://github.com/behenate))
 
 ### 🐛 Bug fixes
 

packages/expo-localization/android/src/main/java/expo/modules/localization/LocalizationModule.kt

@@ -120,15 +120,6 @@ class LocalizationModule : Module() {
       }
     }
 
-  private fun getRegionCode(locale: Locale): String? {
-    val miuiRegion = getSystemProperty("ro.miui.region")
-    return if (!TextUtils.isEmpty(miuiRegion)) {
-      miuiRegion
-    } else {
-      getCountryCode(locale)
-    }
-  }
-
   private fun getMeasurementSystem(locale: Locale): String? {
     return if (VERSION.SDK_INT >= VERSION_CODES.P) {
       when (LocaleData.getMeasurementSystem(ULocale.forLocale(locale))) {
@@ -167,6 +158,7 @@ class LocalizationModule : Module() {
 
             // currency symbol can be localized to display locale (1st on the list) or to the locale for the currency (as done here).
             "currencySymbol" to Currency.getInstance(locale).getSymbol(locale),
+            "temperatureUnit" to getTemperatureUnit(locale),
           )
         )
       } catch (e: Exception) {

packages/expo-localization/android/src/main/java/expo/modules/localization/LocalizationUtils.kt

@@ -5,6 +5,9 @@ import java.util.*
 
 val USES_IMPERIAL = listOf("US", "LR", "MM")
 
+// https://wisevoter.com/country-rankings/countries-that-use-fahrenheit/
+val USES_FAHRENHEIT = listOf("AG", "BZ", "VG", "FM", "MH", "MS", "KN", "BS", "CY", "TC", "US", "LR", "PW", "KY")
+
 val ISOCurrencyCodes: Array<String> by lazy {
   Currency.getAvailableCurrencies().map { it.currencyCode as String }.toTypedArray()
 }
@@ -32,3 +35,17 @@ fun getCurrencyCode(locale: Locale): String? {
     currency?.currencyCode
   }.getOrNull()
 }
+
+fun getRegionCode(locale: Locale): String? {
+  val miuiRegion = getSystemProperty("ro.miui.region")
+  return if (!TextUtils.isEmpty(miuiRegion)) {
+    miuiRegion
+  } else {
+    getCountryCode(locale)
+  }
+}
+
+fun getTemperatureUnit(locale: Locale): String? {
+  val countryCode = getRegionCode(locale) ?: return null
+  return if (USES_FAHRENHEIT.contains(countryCode)) "fahrenheit" else "celsius"
+}