Define behaviour when no time zone is used within a region

[anba]

TimeZonesOfLocale ( loc )

• Define behaviour when region is an unsupported region.
• For example what is the return value of TimeZonesOfLocale("und-ZX"), where "ZX" isn't a registered region subtag, or what is returned for TimeZonesOfLocale("und-ZZ"), where "ZZ" is the unknown region placeholder, also what should be returned for larger regions like TimeZonesOfLocale("und-019"), where "019" is the region subtag for the Americas?

[FrankYFTang]

Currently it is defined as "of those in common use in region."
I am not sure do we need to be more specific than that. Do you have any specific suggestion of how to specify?

[anba]

The current specification requires that the array returned from TimeZonesOfLocale has at least one element. Should implementations just make up the most commonly used time zone when no actual data is present?

For example here's what V8 returns for the specific cases mentioned above:

d8> new Intl.Locale("und-ZX").timeZones
[]
d8> new Intl.Locale("und-ZZ").timeZones
[]
d8> new Intl.Locale("und-019").timeZones
[]

This is clearly not compliant to the current specification, because the returned array has zero elements, but at least one element is required to be returned.

[FrankYFTang]

hum... make sense
should we change
"Let list be a List of 1 or more unique time zone identifiers,"
to
"Let list be a List of 0 or more unique time zone identifiers," ?

[anba]

Let list be a List of 0 or more unique time zone identifiers, [...], of those in common use in region.

"0 or more" reads a bit strange to me when we want to express the list can have any number of elements.

What about something along the lines of:

Let list be a List of unique time zone identifiers, [...], of those in common use in region. If no time zones are commonly used in region, let list be a new empty List.

This way we explicitly say under which conditions the list can be empty.

[ByteEater-pl]

Should implementations just make up the most commonly used time zone when no actual data is present?

How about GMT?