fix(DatePipe): parse string input ourselves to avoid inconsistency between browsers - #13895

@DzmitryShylovich do you have any source reference for this RegExp?

it's from ng1 https://github.com/angular/angular.js/blob/master/src/ng/filter/filters.js#L581

This is super-light on tests.... I would expect that a change like this comes with much, more tests for both valid and invalid cases.

As a comment for the existing test: if we expect sth to not throw we should assert what should be the exact result, not just the fact that it doesn't throw.

As mentioned above, my biggest grip with this PR is that we don't have enough tests... As the very minimum we should:

• add tests that demonstrate what happens for invalid inputs (ex.: 2015-06-15Taaaaa
• what is the output for "valid" cases - as of today this PR just check that we don't throw but I could make those tests pass by deleting all the code from the pipe...

What happens if the input is a string but not a valid ISO string? If I'm reading the code correctly it will still try to create Date object, right? But what is the point if we know that the string is invalid?

will still try to create Date object, right?

yeap. afaik there's no universal pattern for a iso 8601 date. So even if a string doesn't match our regex it can still be a valid date in some browsers. Sort of a fallback. But we can probably remove

} else {
   date = new Date(value);
}

Yes, I think that we should decide if we parse date ourselves or still mess with the Date object. If I'm reading things correctly ng1 is taking over parsing completely: https://github.com/angular/angular.js/blob/dea8ae9af0e59b6727f3f732ea1fae8bb4368b0a/src/ng/filter/filters.js#L613-L623

So even if a string doesn't match our regex it can still be a valid date in some browsers.

Do you have examples? Or is it sth that you suspect?

As mentioned above, my biggest grip with this PR is that we don't have enough tests... As the very minimum we should:

• add tests that demonstrate what happens for invalid inputs (ex.: 2015-06-15Taaaaa
• what is the output for "valid" cases - as of today this PR just check that we don't throw but I could make those tests pass by deleting all the code from the pipe...