There are a few FIXMEs that will need to be addressed, but this
implements most of the prototype method. The FIXMEs are mostly related
to range formatting, which has been entirely ignored so far. But other
than that, the following will need to be addressed:
* Determining flexible day periods must be made locale-aware.
* DST will need to be determined and acted upon.
* Time zones other than UTC and calendars other than Gregorian are
ignored.
* Some of our results differ from other engines as they have some
format patterns we do not. For example, they seem to have a lonely
{dayPeriod} pattern, whereas our closest pattern is
"{hour} {dayPeriod}".
This was an oversight in e42d954743.
These fields should always follow the locale preference in the CLDR.
Overriding these fields would permit formats like "h:mm:ss" to result in
strings like "1:2:3" instead of "1:02:03".
TR-35's Matching Skeleton algorithm dictates how user requests including
fractional second digits should be handled when the CLDR format pattern
does not include that field. When the format pattern contains {second},
but does not contain {fractionalSecondDigits}, generate a second pattern
which appends "{decimal}{fractionalSecondDigits}" to the {second} field.
This is not a calendar supported by ECMA-402, so let's not waste space
with its data.
Further, don't generate "gregorian" as a valid Unicode locale extension
keyword. It's an invalid type identifier, thus cannot be used in locales
such as "en-u-ca-gregorian".
This adds plumbing for the Intl.DateTimeFormat object, constructor, and
prototype.
Note that unlike other Intl objects, the Intl.DateTimeFormat object has
a LibUnicode structure as a base. This is to prevent wild amounts of
code duplication between LibUnicode, Intl.DateTimeFormat, and other
not-yet-defined Intl structures, because there's 12 fields shared
between them.
Turns out the only difference between our existing implementation and
the ECMA-402 implementation is we weren't passing the locales and
options list to each element.toLocaleString invocation.
This also adds spec comments to the definition.
Currently, we get the following results
-1 - -2 = -1
-2 - -1 = 1
Correct would be:
-1 - -2 = 1
-2 - -1 = -1
This was already attempted to be fixed in 7ed8970, but that change was
incorrect. This directly translates to LibJS BigInts having the same
incorrect behavior - it even was tested.
