fix(datepicker): allow date or datetime strings in fromIso8601 (#7220)

Author: mmalerba

src/lib/core/datetime/native-date-adapter.spec.ts

@@ -336,8 +336,11 @@ describe('NativeDateAdapter', () => {
     expect(adapter.fromIso8601('1985-04-12T23:20:50.52Z')).not.toBeNull();
     expect(adapter.fromIso8601('1996-12-19T16:39:57-08:00')).not.toBeNull();
     expect(adapter.fromIso8601('1937-01-01T12:00:27.87+00:20')).not.toBeNull();
+    expect(adapter.fromIso8601('2017-01-01')).not.toBeNull();
+    expect(adapter.fromIso8601('2017-01-01T00:00:00')).not.toBeNull();
     expect(adapter.fromIso8601('1990-13-31T23:59:00Z')).toBeNull();
     expect(adapter.fromIso8601('1/1/2017')).toBeNull();
+    expect(adapter.fromIso8601('2017-01-01T')).toBeNull();
   });
 });
 

src/lib/core/datetime/native-date-adapter.ts

@@ -44,7 +44,7 @@ const DEFAULT_DAY_OF_WEEK_NAMES = {
  * because the regex will match strings an with out of bounds month, date, etc.
  */
 const ISO_8601_REGEX =
-    /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|(?:(?:\+|-)\d{2}:\d{2}))$/;
+    /^\d{4}-\d{2}-\d{2}(?:T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|(?:(?:\+|-)\d{2}:\d{2}))?)?$/;
 
 
 /** Creates an array and fills it with values. */