Implement swapRange functionality for date range selection in DatePicker

Author: ilchenkoArtem

src/day.tsx

@@ -67,6 +67,7 @@ interface DayProps
   locale?: Locale;
   monthShowsDuplicateDaysEnd?: boolean;
   monthShowsDuplicateDaysStart?: boolean;
+  swapRange?: boolean;
 }
 
 /**
@@ -288,6 +289,7 @@ export default class Day extends Component<DayProps> {
       selectsRange,
       selectsDisabledDaysInRange,
       startDate,
+      swapRange,
       endDate,
     } = this.props;
 
@@ -317,13 +319,18 @@ export default class Day extends Component<DayProps> {
       return isDayInRange(day, startDate, selectingDate);
     }
 
-    if (
-      selectsRange &&
-      startDate &&
-      !endDate &&
-      (isAfter(selectingDate, startDate) || isEqual(selectingDate, startDate))
-    ) {
-      return isDayInRange(day, startDate, selectingDate);
+    if (selectsRange && startDate && !endDate) {
+      if (isEqual(selectingDate, startDate)) {
+        return isDayInRange(day, startDate, selectingDate);
+      }
+
+      if (isAfter(selectingDate, startDate)) {
+        return isDayInRange(day, startDate, selectingDate);
+      }
+
+      if (swapRange && isBefore(selectingDate, startDate)) {
+        return isDayInRange(day, selectingDate, startDate);
+      }
     }
 
     return false;

src/month.tsx

@@ -1101,6 +1101,8 @@ export default class Month extends Component<MonthProps> {
       ? ariaLabelPrefix.trim() + " "
       : "";
 
+    console.log('Month render:', this.props.selectingDate);
+
     return (
       <div
         className={this.getClassNames()}

src/test/day_test.test.tsx

@@ -896,6 +896,61 @@ describe("Day", () => {
         ).toBe(true);
       });
     });
+
+    describe("for a date picker with selectsRange and swapRange prop", () => {
+      it("should select range from startDate to selectingDate if selectingDate mote then startDate", () => {
+        const startDate = newDate();
+        const dayInRange = addDays(startDate, 1);
+        const selectingDate = addDays(startDate, 2);
+
+        const containerStartDay = renderDay(dayInRange, {
+          startDate,
+          selectingDate,
+          selectsRange: true,
+          swapRange: true,
+        });
+        expect(
+          containerStartDay
+            .querySelector(".react-datepicker__day")
+            ?.classList.contains(rangeDayClassName),
+        ).toBe(true);
+      })
+
+      it("should select range from selectingDate to startDate if selectingDate less then startDate", () => {
+        const startDate = newDate();
+        const dayInRange = subDays(startDate, 1);
+        const selectingDate = subDays(startDate, 2);
+
+        const containerStartDay = renderDay(dayInRange, {
+          startDate,
+          selectingDate,
+          selectsRange: true,
+          swapRange: true,
+        });
+        expect(
+          containerStartDay
+            .querySelector(".react-datepicker__day")
+            ?.classList.contains(rangeDayClassName),
+        ).toBe(true);
+      });
+
+      it("should select as range if selectingDate is equal to startDate", () => {
+        const startDate = newDate();
+        const selectingDate = startDate
+
+        const containerStartDay = renderDay(startDate, {
+          startDate,
+          selectingDate,
+          selectsRange: true,
+          swapRange: true,
+        });
+        expect(
+          containerStartDay
+            .querySelector(".react-datepicker__day")
+            ?.classList.contains(rangeDayClassName),
+        ).toBe(true);
+      });
+    })
   });
 
   describe("today", () => {