Add zoneOffset cache to resetCaches

src/datetime.js

@@ -389,14 +389,14 @@ function normalizeUnitWithLocalWeeks(unit) {
 // higher-order units from tsNow (as we do in fromObject, this requires that
 // offset is calculated from tsNow).
 function guessOffsetForZone(zone) {
-  if (!DateTime._zoneOffsetGuessCache[zone]) {
-    if (DateTime._zoneOffsetTs === undefined) {
-      DateTime._zoneOffsetTs = Settings.now();
+  if (!zoneOffsetGuessCache[zone]) {
+    if (zoneOffsetTs === undefined) {
+      zoneOffsetTs = Settings.now();
     }
 
-    DateTime._zoneOffsetGuessCache[zone] = zone.offset(DateTime._zoneOffsetTs);
+    zoneOffsetGuessCache[zone] = zone.offset(zoneOffsetTs);
   }
-  return DateTime._zoneOffsetGuessCache[zone];
+  return zoneOffsetGuessCache[zone];
 }
 
 // this is a dumbed down version of fromObject() that runs about 60% faster
@@ -472,6 +472,18 @@ function lastOpts(argList) {
   return [opts, args];
 }
 
+/**
+ * Timestamp to use for cached zone offset guesses (exposed for test)
+ */
+let zoneOffsetTs;
+/**
+ * Cache for zone offset guesses (exposed for test).
+ *
+ * This optimizes quickDT via guessOffsetForZone to avoid repeated calls of
+ * zone.offset().
+ */
+let zoneOffsetGuessCache = {};
+
 /**
  * A DateTime is an immutable data structure representing a specific date and time and accompanying methods. It contains class and instance methods for creating, parsing, interrogating, transforming, and formatting them.
  *
@@ -558,22 +570,6 @@ export default class DateTime {
     this.isLuxonDateTime = true;
   }
 
-  /**
-   * Timestamp to use for cached zone offset guesses (exposed for test)
-   *
-   * @access private
-   */
-  static _zoneOffsetTs;
-  /**
-   * Cache for zone offset guesses (exposed for test).
-   *
-   * This optimizes quickDT via guessOffsetForZone to avoid repeated calls of
-   * zone.offset().
-   *
-   * @access private
-   */
-  static _zoneOffsetGuessCache = {};
-
   // CONSTRUCT
 
   /**
@@ -1038,6 +1034,11 @@ export default class DateTime {
     return expanded.map((t) => t.val).join("");
   }
 
+  static resetCache() {
+    zoneOffsetTs = undefined;
+    zoneOffsetGuessCache = {};
+  }
+
   // INFO
 
   /**

src/settings.js

@@ -1,6 +1,7 @@
 import SystemZone from "./zones/systemZone.js";
 import IANAZone from "./zones/IANAZone.js";
 import Locale from "./impl/locale.js";
+import DateTime from "./datetime.js";
 
 import { normalizeZone } from "./impl/zoneUtil.js";
 import { validateWeekSettings } from "./impl/util.js";
@@ -171,5 +172,6 @@ export default class Settings {
   static resetCaches() {
     Locale.resetCache();
     IANAZone.resetCache();
+    DateTime.resetCache();
   }
 }

test/datetime/dst.test.js

@@ -39,8 +39,7 @@ for (const [name, local] of Object.entries(dateTimeConstructors)) {
       test("Ambiguous dates pick the one with the cached offset", () => {
         const oldSettings = Settings.now;
         try {
-          DateTime._zoneOffsetGuessCache = {};
-          DateTime._zoneOffsetTs = undefined;
+          Settings.resetCaches();
           Settings.now = () => 1495653314595; // May 24, 2017
           let d = local(2017, 11, 5, 1);
           expect(d.hour).toBe(1);
@@ -51,8 +50,7 @@ for (const [name, local] of Object.entries(dateTimeConstructors)) {
           expect(d.hour).toBe(1);
           expect(d.offset).toBe(-4 * 60);
 
-          DateTime._zoneOffsetGuessCache = {};
-          DateTime._zoneOffsetTs = undefined;
+          Settings.resetCaches();
 
           Settings.now = () => 1484456400000; // Jan 15, 2017
           d = local(2017, 11, 5, 1);
@@ -171,8 +169,7 @@ describe("DateTime.local() with offset caching", () => {
           const oldSettings = Settings.now;
           try {
             Settings.now = () => cacheTs;
-            DateTime._zoneOffsetGuessCache = {};
-            DateTime._zoneOffsetTs = undefined;
+            Settings.resetCaches();
             // load cache
             DateTime.local(2020, 1, 1, 0, zoneObj);