Loose type check against dates in rest_validate_value_from_schema causes invalidation for valid timestamp

[jonmcpartland]

When validating dates, rest_validate_value_from_schema assumes a falsy return value from rest_parse_date always means that the date is invalid (see [wp-includes/rest-api.php@L2138](​https://github.com/WordPress/wordpress-develop/blob/5.7/src/wp-includes/rest-api.php#L2138). This is correct in all but one case (to my knowledge).

A perfectly valid date would be 1970-01-01 00:00:00. However, since that date would produce a return value from rest_parse_date of 0, rest_validate_value_from_schema assumes it is invalid.

Since rest_parse_date returns the return value of strtotime, checking that the return value is false — rather than falsy — would be sufficient to resolve.

[johnbillion]

Welcome @jonmcpartland , good catch! This seems correct to me but it would benefit from some tests.

​https://make.wordpress.org/core/handbook/testing/automated-testing/phpunit/

[jonmcpartland]

Hi @johnbillion

Thanks for the feedback. I am attaching a new diff with added unit tests.

Best
Jon

[jonmcpartland]

patch with tests