* Fix Issue 1441 (isDateTime and Formulas)
When you have a date-field which is a formula, isDateTime returns false.
https://github.com/PHPOffice/PhpSpreadsheet/issues/1441
Report makes sense; fixed as suggested. Also fixed a few minor
related issues, and added tests so that Shared/Date and Shared/TimeZone
are now completely covered.
Date/setDefaultTimeZone and TimeZone/setTimeZone were not consistent
about what to do in event of failure - return false or throw.
They will now both return false, which is what Date's function
said it would do in its doc block anyhow. Date/validateTimeZone will
continue to throw; it was protected, but was never called outside
Date, so I changed it to private.
TimeZone/getTimeZoneAdjustment checked for 'UST' when it probably
meant 'UTC', and, as it turns out, the check is not even needed.
The most serious problem was that TimeZone/validateTimeZone does not
check the backwards-compatible time zones. The timezone project
aggressively, and very controversially, "demotes" timezones;
such timezones eventually wind up in the PHP backwards-compatible list.
We want to make sure to check that list so that our applications do not
break when this happens.
While investigating something else in Shared, I noticed that CodePage
had poor test coverage and a high complexity rating. This change
addresses both; Scrutinizer would love it, although its interface on
GitHub seems broken at the moment (all PRs show "Waiting for External
Code Coverage").
Because even if it doesn't make a difference in practice, it is
technically more correct to call static methods statically. It
also better advertise that those methods can be used from any context.
Control characters in cell values are automatically escaped without
the need to excplicitly call `StringHelper::buildCharacterSets()` beforehand.
Fixes#212
oleibman