Re: [xwiki-devs] [Brainstorming] Handling "young" APIs for backward compatibility

On Thu, May 3, 2012 at 3:24 PM, Denis Gervalle <dgl(a)softec.lu> wrote: > On Thu, May 3, 2012 at 9:47 AM, Vincent Massol <vincent(a)massol.net> wrote: > >> Hi devs, >> >> We have recently voted a rule where we said that we will do the following: >> * Always deprecate APIs >> * Always move them to Legacy modules >> * And when there's a technical issue to moving stuff to the Legacy module, >> only then, send a VOTE to remove an API >> (see http://markmail.org/message/tino4ngttflc5i3s). >> >> This means that from now on (starting on 26th of April 2012) we're not >> allowed to put excludes in CLIRR. >> >> However I've seen that we have added some CLIRR excludes after the vote >> was passed. >> >> I believe that the main issue we have is for "young" APIs that are not >> considered stable. >> >> Proposal 1: Internal package >> ========= >> >> * Young APIs must be located in the "internal" package till they become >> stable. I propose "internal" to reuse an existing package that we filter >> when testing for CLIRR. "internal" means that users should not use this API >> because it's considered unstable and can change at any time. >> * When a Young API is considered stable enough and we want to open it to >> public consumption then we move it from "internal" to its target package >> (that's easy to with IDEs). From that point forward any changes to them >> goes through the standard mechanism of deprecation/legacy. >> > > This is not always so easy. It really depends on what we are working on. If > this is a small, or minor addition, this should works, but for really new > experimental features, this does not fit (ie: security component). First, > you will mixup internal and experimental, which will not shows the intends > and not helps collaborating on the new feature. Second, this will also > influence the place for tests, which will need to be moved later as well. > Third, you will not see potential access issue (package access), since you > will mix packages that will be later split. > > >> * If we want to add a new method to an existing public API then this >> should not be considered a "young" API. It's just an addition to an >> existing API and thus goes directly to the deprecation/legacy cycle. >> * We need to be careful to isolate "young" APIs from public API so that >> users don't inadvertently use "young" unstable APIs by mistake. If not >> possible then directly go through the deprecation/legacy cycle. >> >> The advantage of this proposal is that it doesn't change our current >> practices and is very easy to verify through CLIRR. >> >> Proposal 2: Experimental package >> ========= >> >> Another possibility I can think of is to introduce a new "experimental" >> package instead of reusing the "internal" one. It has the advantage of >> being able to follow "young" APIs and ensure they don't stay in that state >> indefinitely, while still allowing the user who uses it to notice it's >> experimental. >> > > This should solve most of the above inconvenient, but I am not sure we > really need that for new feature. Declaring the feature as experimental in > the RN should be enough IMO. > > >> >> Proposal 3: Experimental Annotation >> ========= > > >> Another idea is to just use an @Experimental javadoc tag for experimental >> code. It has the advantage of using the target package but it has drawbacks: >> * It's impossible for users to notice that they're using Experimental APIs >> since when they import a class they won't see anything that'll tell them >> they're using a "young" API >> * It's almost impossible to tell CLIRR to exclude those APIs from its >> checks. The only way to do this is to modify the source code of the CLIRR >> plugin AFAIK. Thus we would need to exclude those manually using CLIRR >> excludes and thus before we release we would need to go over the full list >> of CLIRR excludes to ensure the excludes listed are only for "young" APIs >> marked "experimental". >> >> Note that I mentioned javadoc tag and not annotation because I believe we >> need to add information about when the Experimental API was first >> introduced so that we eventually move it as a proper API by removing the >> Experimental tag. Maybe we would need a rule such as: keep that tag for >> less or equal to 3 full minor releases (i.e. 6 months). >> > > But you have titled Annotation, which is confusing !

Pretty much the same concerns than Denis: it's not as easy as you think to change package of a big project like rights or extension manager all the sudden. But I would vote -1 for 1) and -0 for 2) which is a bit better. IMO 3) is enough even if not perfect either. Also about adding new methods, that's really not the main issue of an experimental API in which we can potentially rename a bunch of methods because of a design change and an old API has the exact same issue so none of the proposal help in any way for this.