feat(common): Add ISO week-numbering year formats support to formatDate (#38828)

Add ISO 8601 week-numbering year formats ('r', 'rr', 'rrr', 'rrrr') support for formatDate function.

Issue:https://github.com/angular/angular/issues/38739

PR Close #38828

packages/common/src/i18n/format_date.ts

@@ -13,7 +13,7 @@ export const ISO8601_DATE_REGEX =
 //    1        2       3         4          5          6          7          8  9     10      11
 const NAMED_FORMATS: {[localeId: string]: {[format: string]: string}} = {};
 const DATE_FORMATS_SPLIT =
-    /((?:[^GyMLwWdEabBhHmsSzZO']+)|(?:'(?:[^']|'')*')|(?:G{1,5}|y{1,4}|M{1,5}|L{1,5}|w{1,2}|W{1}|d{1,2}|E{1,6}|a{1,5}|b{1,5}|B{1,5}|h{1,2}|H{1,2}|m{1,2}|s{1,2}|S{1,3}|z{1,4}|Z{1,5}|O{1,4}))([\s\S]*)/;
+    /((?:[^GyrMLwWdEabBhHmsSzZO']+)|(?:'(?:[^']|'')*')|(?:G{1,5}|y{1,4}|r{1,4}|M{1,5}|L{1,5}|w{1,2}|W{1}|d{1,2}|E{1,6}|a{1,5}|b{1,5}|B{1,5}|h{1,2}|H{1,2}|m{1,2}|s{1,2}|S{1,3}|z{1,4}|Z{1,5}|O{1,4}))([\s\S]*)/;
 
 enum ZoneWidth {
   Short,
@@ -394,6 +394,18 @@ function weekGetter(size: number, monthBased = false): DateFormatter {
   };
 }
 
+/**
+ * Returns a date formatter that provides the week-numbering year for the input date.
+ */
+function weekNumberingYearGetter(size: number, trim = false): DateFormatter {
+  return function(date: Date, locale: string) {
+    const thisThurs = getThursdayThisWeek(date);
+    const weekNumberingYear = thisThurs.getFullYear();
+    return padNumber(
+        weekNumberingYear, size, getLocaleNumberSymbol(locale, NumberSymbol.MinusSign), trim);
+  };
+}
+
 type DateFormatter = (date: Date, locale: string, offset: number) => string;
 
 const DATE_FORMATS: {[format: string]: DateFormatter} = {};
@@ -438,6 +450,25 @@ function getDateFormatter(format: string): DateFormatter|null {
       formatter = dateGetter(DateType.FullYear, 4, 0, false, true);
       break;
 
+    // 1 digit representation of the week-numbering year, e.g. (AD 1 => 1, AD 199 => 199)
+    case 'r':
+      formatter = weekNumberingYearGetter(1);
+      break;
+    // 2 digit representation of the week-numbering year, padded (00-99). (e.g. AD 2001 => 01, AD
+    // 2010 => 10)
+    case 'rr':
+      formatter = weekNumberingYearGetter(2, true);
+      break;
+    // 3 digit representation of the week-numbering year, padded (000-999). (e.g. AD 1 => 001, AD
+    // 2010 => 2010)
+    case 'rrr':
+      formatter = weekNumberingYearGetter(3);
+      break;
+    // 4 digit representation of the week-numbering year (e.g. AD 1 => 0001, AD 2010 => 2010)
+    case 'rrrr':
+      formatter = weekNumberingYearGetter(4);
+      break;
+
     // Month of the year (1-12), numeric
     case 'M':
     case 'L':

packages/common/src/pipes/date_pipe.ts

@@ -65,6 +65,10 @@ import {invalidPipeArgumentError} from './invalid_pipe_argument_error';
  *  |                    | yy          | Numeric: 2 digits + zero padded                               | 02, 20, 01, 17, 73                                         |
  *  |                    | yyy         | Numeric: 3 digits + zero padded                               | 002, 020, 201, 2017, 20173                                 |
  *  |                    | yyyy        | Numeric: 4 digits or more + zero padded                       | 0002, 0020, 0201, 2017, 20173                              |
+ *  | Week-numbering year| r           | Numeric: minimum digits                                       | 2, 20, 201, 2017, 20173                                    |
+ *  |                    | rr          | Numeric: 2 digits + zero padded                               | 02, 20, 01, 17, 73                                         |
+ *  |                    | rrr         | Numeric: 3 digits + zero padded                               | 002, 020, 201, 2017, 20173                                 |
+ *  |                    | rrrr        | Numeric: 4 digits or more + zero padded                       | 0002, 0020, 0201, 2017, 20173                              |
  *  | Month              | M           | Numeric: 1 digit                                              | 9, 12                                                      |
  *  |                    | MM          | Numeric: 2 digits + zero padded                               | 09, 12                                                     |
  *  |                    | MMM         | Abbreviated                                                   | Sep                                                        |

packages/common/test/i18n/format_date_spec.ts

@@ -95,6 +95,10 @@ describe('Format date', () => {
         yy: '15',
         yyy: '2015',
         yyyy: '2015',
+        r: '2015',
+        rr: '15',
+        rrr: '2015',
+        rrrr: '2015',
         M: '6',
         MM: '06',
         MMM: 'Jun',
@@ -153,6 +157,10 @@ describe('Format date', () => {
         yy: '15',
         yyy: '2015',
         yyyy: '2015',
+        r: '2015',
+        rr: '15',
+        rrr: '2015',
+        rrrr: '2015',
         M: '1',
         MM: '01',
         MMM: 'Jan',
@@ -361,5 +369,14 @@ describe('Format date', () => {
       expect(formatDate(3001, 'm:ss.SS', 'en')).toEqual('0:03.00');
       expect(formatDate(3001, 'm:ss.SSS', 'en')).toEqual('0:03.001');
     });
+
+    // https://github.com/angular/angular/issues/38739
+    it('should return correct ISO 8601 week-numbering year for dates close to year end/beginning',
+       () => {
+         expect(formatDate('2013-12-27', 'rrrr', 'en')).toEqual('2013');
+         expect(formatDate('2013-12-29', 'rrrr', 'en')).toEqual('2014');
+         expect(formatDate('2010-01-02', 'rrrr', 'en')).toEqual('2009');
+         expect(formatDate('2010-01-04', 'rrrr', 'en')).toEqual('2010');
+       });
   });
 });