fix(month picker): prevent duplicates (#1377)

src/framework/theme/components/calendar-kit/components/calendar-month-picker/calendar-month-picker.component.spec.ts

@@ -43,5 +43,18 @@ describe('Component: NbCalendarMonthPicker', () => {
     componentEl.query(By.css('nb-calendar-picker'))
       .nativeElement
       .dispatchEvent(new CustomEvent('select'));
-  })
+  });
+
+  it('should not have duplicate months', () => {
+    component.month = new Date(2019, 0, 30);
+    component.initMonths();
+
+    let expectedMonthIndex = 0;
+    for (const monthRow of component.months) {
+      for (const month of monthRow) {
+        expect(month.getMonth()).toEqual(expectedMonthIndex);
+        expectedMonthIndex++;
+      }
+    }
+  });
 });

src/framework/theme/components/calendar-kit/components/calendar-month-picker/calendar-month-picker.component.ts

@@ -14,7 +14,7 @@ import {
   Output,
   Type,
 } from '@angular/core';
-import { batch, range } from '../../helpers';
+import { batch } from '../../helpers';
 import { NbCalendarCell, NbCalendarSize } from '../../model';
 import { NbCalendarMonthCellComponent } from './calendar-month-cell.component';
 import { NbDateService } from '../../services';
@@ -75,15 +75,19 @@ export class NbCalendarMonthPickerComponent<D, T> implements OnInit {
   }
 
   initMonths() {
-    const months: D[] = range(MONTHS_IN_VIEW).map(i => this.createMonthDateByIndex(i));
+    const date = this.dateService.getDate(this.month);
+    const year = this.dateService.getYear(this.month);
+    const firstMonth = this.dateService.createDate(year, 0, date);
+    const months = [ firstMonth ];
+
+    for (let monthIndex = 1; monthIndex < MONTHS_IN_VIEW; monthIndex++) {
+      months.push(this.dateService.addMonth(firstMonth, monthIndex));
+    }
+
     this.months = batch(months, MONTHS_IN_COLUMN);
   }
 
   onSelect(month: D) {
     this.monthChange.emit(month);
   }
-
-  private createMonthDateByIndex(i: number): D {
-    return this.dateService.createDate(this.dateService.getYear(this.month), i, this.dateService.getDate(this.month));
-  }
 }