Versioning conundrum for Noda Time – help requested

Obviously I'd normally ask developer questions on Stack Overflow but in this case, it feels like the answers may be at least somewhat opinion-based. If it turns out that it's sufficiently straightforward that a Stack Overflow question and answer would be useful, I can always repost it there later.

The Facts

Noda Time 1.x exists "in production", and the latest version is 1.3.1. This targets .NET 3.5 Client profile, .NET 4.0, and PCL Profile 328 (in a directory of lib\portable-net4+sl5+netcore45+wpa81+wp8+MonoAndroid1+MonoTouch1+XamariniOS1)

Noda Time currently includes the IANA time zone data ("TZDB") - each released version of Noda Time contains the TZDB version that was "most recent" at the time that the Noda Time release was built. This gets out of date quite quickly, as there are multiple releases of TZDB every year. Those releases are named 2016a, 2016b etc. Noda Time also provides the ability to read .nzd files (Noda Zone Data - a custom format) and every time there's a new release of TZDB, I build a .nzd file and upload it to nodatime.org, updating http://nodatime.org/tzdb/latest.txt to point to the latest version.

Noda Time 2.0 has not been released yet. When I do release it, I expect to target .NET 4.5 and netstandard1.0.

Each Noda Time 1.x release has an AssemblyVersion just based on major/minor, i.e. 1.0, 1.1, 1.2 etc. Based on this blog post, this may have been a mistake - it should quite possibly have been 1.0 for all versions. Obviously I can't fix that now, but I can make the 2.x releases use 2.0 everywhere.

When 2.0 is "pretty much ready" we're going to cut a 1.4 release which deprecates things that are removed in 2.0 and provides the new approaches as far as possible. For example, the IClock.Now property from 1.x is removed in 2.0, and replaced by IClock.GetCurrentInstant(). We'll deprecate the Now property and introduce a GetCurrentInstant() extension method which delegates to it. This shouldn't break any 1.x users, but should allow them to move over to the new API as far as possible before upgrading to 2.0. The intention is that users wouldn't stay on 1.4 for very long. (Obviously they could do so, but there's not a lot of benefit. 1.4 won't have new features - it's really just a transition version.)

So far, that's just the way of the world. Now I want to make it easier for users to stay up-to-date with TZDB - including if nodatime.org goes down. (That's considerably more likely than nuget.org going down, for example.)

The plan is to introduce a new nearly-data-only assembly, packaged as NodaTime.Tzdb. The aim is to allow users to update their data dependency at build time, in a controlled fashion. If you only want to specify an exact version to depend on, you can do so. If you want to pick up the latest version every time you build, that should be possible too.

The tricky bits come in terms of the versioning.

Some options

Firstly, the versioning scheme for the package ignoring everything else. I plan to use something like this:

• 2016a => 1.2016.1
• 2016b => 1.2016.2
• 2016c => 1.2016.3
• "
• 2017a => 1.2017.1

This should make it reasonably easy to tell the TZDB version just from the package version.

However, I'm considering a few options within this idea:

• I could create a single package per TZDB release, targeting .NET 3.5 client profile, .NET 4.0, the Profile 328 PCL, .NET 4.5, and .NET Standard 1.0. The first four of these could depend on Noda Time 1.1, and the last one would have to depend on Noda Time 2.0.
• I could do the above, but depend on 1.3.1 instead of 1.1.
• I could create one package with two versions per TZDB release - a 1.x depending on Noda Time 1.1, and a 2.x depending on Noda Time 2.0. For example, when TZDB 2016d is released, I could create 1.2016.4 and 2.2016.4.
• I could create one package version depending on 1.1, one depending on 1.2, one depending on 1.3, one depending on 1.4 (when that exists) and one depending on 2.0.
• I could create two separate packages, i.e. include the Noda Time major version number in the package name. I don't like this idea, but it's on the table.

Some concerns and questions

There are various aspects to this which cause me a few worries. I'm not sure how well I can really structure or segregate those, so I'll just list them.

• Can a non-prerelease package depend on a prerelease package for some frameworks? If not, that possibly blows the "single version" idea out of the water, as I can't depend on NodaTime v2.0 yet - it's not out.
• Even if that's feasible, is it sane to depend on different major versions of the NodaTime package from within a single version of the NodaTime.Tzdb package, or is that going to cause massive confusion?
• Should I depend on NodaTime v1.1 or v1.3.1? They have different AssemblyVersion numbers, which I believe means an assembly binding redirect will be required if I depend on 1.1 but users depend on 1.3.1. To be clear, I don't expect many users to still be on versions older than 1.3.1.
• Likewise, is it going to cause issues for .NET 4.5 users who use NodaTime 2.0 (eventually) if they depend on a version of NodaTime.Tzdb that depends on NodaTime 1.3.1? Again, presumably assembly binding redirects are needed.
• If I go with the "two-version" scheme (i.e. 1.2016.4 and 2.2016.4 etc) how careful would NodaTime 1.3.1 users have to be? I wouldn't want them to accidentally get upgraded to NodaTime 2.0 when that's released, by accidentally taking the 2.x line of NodaTime.Tzdb.
• Does dotnet cli support the nuget allowedVersions feature at all? I haven't found any support for it in DNX, but really it's vital for this scheme to work at all - basically I'd expect a NodaTime 1.3.1 user to specify an allowed version range for NodaTime.Tzdb of [1,2)
• Is my scheme of 1.2016.4 (etc) sensible? It's somewhat abusing major/minor/patch, in that there's no real difference in meaning between a minor version bump ("it's the new year") and a patch bump ("there's been another release in the same year"). Neither kind of change will be breaking (unless you depend on specific time zones behaving in specific ways, of course), and it's handy to be able to give a simple mapping between TZDB version and package version, but there may be consequences I'm unaware of.

Please feel free to ask clarifying questions in comments. Will look forward to getting some answers :)