By default, pipes are pure. This means that an instance of a pipe will be reused and the pipe will be called only when its arguments change.
BREAKING CHANGE
Before:
@Pipe({name: 'date'}) class DatePipe {} defines an impure pipe.
After:
@Pipe({name: 'date'}) class DatePipe {} defines a pure pipe.
@Pipe({name: 'date', pure: false}) class DatePipe {} defines an impure pipe.
Closes#3966
a8bdb693b9