[SR-8078] Some time zone identifiers are not supported by TimeZone type only on Linux

[swift-ci]

Previous ID	SR-8078
Radar	None
Original Reporter	guidomb (JIRA User)
Type	Bug
Status	Closed
Resolution	Done

Environment

Ubuntu 16.04 Swift 4.2 Snapshot 2018-06-21

Additional Detail from JIRA

Votes	0
Component/s	Foundation
Labels	Bug
Assignee	@spevans
Priority	Medium

md5: 97cf690688a2a5cb9c0ffeec6acfa0c9

Issue Description:

The following time zone identifiers which are returned by

TimeZone.knownTimeZoneIdentifiers

when used with

TimeZone.init?(idintifier:)

returns nil:

"America/Fort_Nelson",
"America/Punta_Arenas",
"Asia/Famagusta",
"Asia/Atyrau",
"Asia/Yangon",
"Europe/Kirov",
"Europe/Astrakhan",
"Europe/Saratov",
"Europe/Ulyanovsk",
"Asia/Barnaul",
"Asia/Tomsk"

To easily test this you can use the following code snippet

TimeZone.knownTimeZoneIdentifiers
    .map { ($0, TimeZone(identifier: $0)) }
    .filter { $0.1 == nil }
    .forEach { print("Ofender: \($0)") }

If you run on macOS nothing gets printed but if you run it on Ubuntu 16.04 you get the previous list of identifiers.

You can use https://hub.docker.com/r/guidomb/swift-snapshots/tags/ which I publish and use in my code.

[spevans]

The timezone names get validated by calling the ICU function ucal_getCanonicalTimeZoneID (see https://github.com/apple/swift-corelibs-foundation/blob/master/CoreFoundation/NumberDate.subproj/CFTimeZone.c#L1081)

which is rejecting 'America/Fort_Nelson' and the other names however I'm not sure why this these names are being rejected.

Note that CFTimeZoneCopyKnownNames() (used by knownTimeZoneIdentifiers) doesn't seem to validate that names hence why there are timezone that cannot be instantiated.

Probably needs two fixes:

1. Validate the names in CFTimeZoneCopyKnownNames()
2. Determine why ucal_getCanonicalTimeZoneID excludes those names, this could just be due to the ICU version being older on 16.04, which appears to be the case as the issue does not show up on Ubuntu18.04

[spevans]

#1616