docs(dateFilter): fix docs to match implementation for week no formatting

The existing documentation claims that dateFilter determines week no
according to the ISO8601 standard, but this is not the case as illustrated
by tests in this PR. More specifically, the implementation deviates from
ISO8601 in 2 important aspects:
- impl assumes Sun to be the first day of a week, ISO8601 mandates Mon
- impl allows weeks 0 (for years starting on Fri, Sat) while ISO8601
would mark them as a week 52/53 of a previous year.

Fixes angular#10314
Closes angular#10313

Author: pkozlowski-opensource

src/ng/filter/filters.js

@@ -356,8 +356,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
  *   * `'.sss' or ',sss'`: Millisecond in second, padded (000-999)
  *   * `'a'`: AM/PM marker
  *   * `'Z'`: 4 digit (+sign) representation of the timezone offset (-1200-+1200)
- *   * `'ww'`: ISO-8601 week of year (00-53)
- *   * `'w'`: ISO-8601 week of year (0-53)
+ *   * `'ww'`: Week of year, padded (00-53). Week 01 is assumed to contain the first Thur of a year.
+ *   * `'w'`: Week of year (0-53). Week 1 is assumed to contain the first Thur of a year.
  *
  *   `format` string can also be one of the following predefined
  *   {@link guide/i18n localizable formats}:

test/ng/filter/filtersSpec.js

@@ -1,6 +1,6 @@
 'use strict';
 
-describe('filters', function() {
+ddescribe('filters', function() {
 
   var filter;
 
@@ -326,6 +326,36 @@ describe('filters', function() {
                     toEqual('2010-09-03T06:35:08-0530');
     });
 
+    it('should correctly calculate week number', function () {
+      function formatWeek(dateToFormat) {
+        return date(new angular.mock.TzDate(+5, dateToFormat + 'T12:00:00.000Z'), 'ww (EEE)');
+      }
+
+      expect(formatWeek('2007-01-01')).toEqual('01 (Mon)');
+      expect(formatWeek('2007-12-31')).toEqual('53 (Mon)');
+
+      expect(formatWeek('2008-01-01')).toEqual('01 (Tue)');
+      expect(formatWeek('2008-12-31')).toEqual('53 (Wed)');
+
+      expect(formatWeek('2014-01-01')).toEqual('01 (Wed)');
+      expect(formatWeek('2014-12-31')).toEqual('53 (Wed)');
+
+      expect(formatWeek('2009-01-01')).toEqual('01 (Thu)');
+      expect(formatWeek('2009-12-31')).toEqual('53 (Thu)');
+
+      expect(formatWeek('2010-01-01')).toEqual('00 (Fri)');
+      expect(formatWeek('2010-12-31')).toEqual('52 (Fri)');
+
+      expect(formatWeek('2011-01-01')).toEqual('00 (Sat)');
+      expect(formatWeek('2011-01-02')).toEqual('01 (Sun)');
+      expect(formatWeek('2011-01-03')).toEqual('01 (Mon)');
+      expect(formatWeek('2011-12-31')).toEqual('52 (Sat)');
+
+      expect(formatWeek('2012-01-01')).toEqual('01 (Sun)');
+      expect(formatWeek('2012-01-02')).toEqual('01 (Mon)');
+      expect(formatWeek('2012-12-31')).toEqual('53 (Mon)');
+    });
+
     it('should treat single quoted strings as string literals', function() {
       expect(date(midnight, "yyyy'de' 'a'x'dd' 'adZ' h=H:m:saZ")).
                       toEqual('2010de axdd adZ 12=0:5:8AM-0500');