📝 Commit Details:

backend/node_modules/date-fns/setWeekYear.js

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+import { getDefaultOptions } from "./_lib/defaultOptions.js";
+import { constructFrom } from "./constructFrom.js";
+import { differenceInCalendarDays } from "./differenceInCalendarDays.js";
+import { startOfWeekYear } from "./startOfWeekYear.js";
+import { toDate } from "./toDate.js";
+
+/**
+ * The {@link setWeekYear} function options.
+ */
+
+/**
+ * @name setWeekYear
+ * @category Week-Numbering Year Helpers
+ * @summary Set the local week-numbering year to the given date.
+ *
+ * @description
+ * Set the local week-numbering year to the given date,
+ * saving the week number and the weekday number.
+ * The exact calculation depends on the values of
+ * `options.weekStartsOn` (which is the index of the first day of the week)
+ * and `options.firstWeekContainsDate` (which is the day of January, which is always in
+ * the first week of the week-numbering year)
+ *
+ * Week numbering: https://en.wikipedia.org/wiki/Week#The_ISO_week_date_system
+ *
+ * @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
+ * @typeParam ResultDate - The result `Date` type, it is the type returned from the context function if it is passed, or inferred from the arguments.
+ *
+ * @param date - The date to be changed
+ * @param weekYear - The local week-numbering year of the new date
+ * @param options - An object with options
+ *
+ * @returns The new date with the local week-numbering year set
+ *
+ * @example
+ * // Set the local week-numbering year 2004 to 2 January 2010 with default options:
+ * const result = setWeekYear(new Date(2010, 0, 2), 2004)
+ * //=> Sat Jan 03 2004 00:00:00
+ *
+ * @example
+ * // Set the local week-numbering year 2004 to 2 January 2010,
+ * // if Monday is the first day of week
+ * // and 4 January is always in the first week of the year:
+ * const result = setWeekYear(new Date(2010, 0, 2), 2004, {
+ *   weekStartsOn: 1,
+ *   firstWeekContainsDate: 4
+ * })
+ * //=> Sat Jan 01 2005 00:00:00
+ */
+export function setWeekYear(date, weekYear, options) {
+  const defaultOptions = getDefaultOptions();
+  const firstWeekContainsDate =
+    options?.firstWeekContainsDate ??
+    options?.locale?.options?.firstWeekContainsDate ??
+    defaultOptions.firstWeekContainsDate ??
+    defaultOptions.locale?.options?.firstWeekContainsDate ??
+    1;
+
+  const diff = differenceInCalendarDays(
+    toDate(date, options?.in),
+    startOfWeekYear(date, options),
+    options,
+  );
+
+  const firstWeek = constructFrom(options?.in || date, 0);
+  firstWeek.setFullYear(weekYear, 0, firstWeekContainsDate);
+  firstWeek.setHours(0, 0, 0, 0);
+
+  const date_ = startOfWeekYear(firstWeek, options);
+  date_.setDate(date_.getDate() + diff);
+  return date_;
+}
+
+// Fallback for modularized imports:
+export default setWeekYear;