[SR-2846] Calendar date(byAdding:to:wrappingComponents:) returns nil when it shouldn't

[swift-ci]

Previous ID	SR-2846
Radar	None
Original Reporter	UberJason (JIRA User)
Type	Bug
Status	Closed
Resolution	Done

Environment

This code functions on OS X 10.11 but not in an Ubuntu 14.04 Docker image.

Here's the swift -version output on OS X 10.11:

Apple Swift version 3.0 (swiftlang-800.0.46.2 clang-800.0.38)
Target: x86_64-apple-macosx10.9

And the swift -version output on the Ubuntu 14.04 Docker image:

Swift version 3.0 (swift-3.0-RELEASE)
Target: x86_64-unknown-linux-gnu

Additional Detail from JIRA

Votes	0
Component/s	Foundation
Labels	Bug, Linux
Assignee	None
Priority	Medium

md5: a9665d5c4946832d28b144569d47aae4

Issue Description:

The below snippet of code works on OS X 10.11 El Capitan but not on an Ubuntu 14.04 Docker image with Swift 3.0 RELEASE installed or the October 2 snapshot. Tested in REPL as well as, originally, in a Vapor web application, where I was doing some Date manipulations.

import Foundation

let today = Date()
let diffComponents = DateComponents(day: -1)
let newDate = Calendar.current.date(byAdding: diffComponents, to: today)        //returns nil

A few notes:

• today is a valid Date object

• Calendar.current is a valid Calendar object

• I also tried manually checking that the date(from: DateComponents) function works, and it does:

   todayComponents = DateComponents(year: 2016, month: 10, day: 4) 
  Calendar.current.date(from: todayComponents)        // returns valid Date on both platforms

[alblue]

I think the bug is here:

https://github.com/apple/swift-corelibs-foundation/blob/master/Foundation/NSCalendar.swift#L464

_convert(comps.isLeapMonth, type: "L", vector: &vector, compDesc: &compDesc)

The leap month is defined with a capital letter here, but a lower-case letter when it's decoded:

https://github.com/apple/swift-corelibs-foundation/blob/338f4bf3a89c75a0420b49f5701466e106af02b5/CoreFoundation/Locale.subproj/CFCalendar.c#L423

case 'l': return UCAL_IS_LEAP_MONTH;

The lower-case l should be the correct version so this probably needs to be changed here. In addition, there are optional-of-bool issues here; the 'comps.isLeapMonth' is a boolean value, which means it attempts to roll forward the leap month (which doesn't make sense). I think the error was introduced here, although it didn't help that the capitalisation was also wrong at the time:

d3300b7

[swift-ci]

Comment by Jason Ji (JIRA)

Thanks Alex - I saw your response on the mailing list too, but for posterity's sake I'll re-post my reply here as well:

I came to the same conclusion, with one more minor bug (bringing the total to three): the definition of the date(byAdding:to:options: ) function itself was attempting to do math on CFAbsoluteTime 0.0, rather than the passed-in date's own timeIntervalSinceReferenceDate. I submitted a pull request to fix these issues last night here: #668

Your email address suggests you're with Apple; do you have the ability to review that PR and merge it in if it meets your specs? Our team kind of desperately needs this bug fix, as we can't do date math on our Swift-based server right now. Thanks!!

[swift-ci]

Comment by Jason Ji (JIRA)

I submitted PR #668 on GitHub to fix this issue: #668

[swift-ci]

Comment by Jason Ji (JIRA)

Resolved in PR #668: #668