BJ, is that still the case if we change the return type to a subtype of the original return type?
Ever since Java 5 it has been legal to implement an interface method and return a more specialised type than the interface demands… this would suggest a Minor API change (as long as we’re talking about a Provider Type interface). Neil > On 4 May 2017, at 15:02, BJ Hargrave <hargr...@us.ibm.com> wrote: > > This is not true from a binary compatibility point of view. See > https://docs.oracle.com/javase/specs/jls/se7/html/jls-13.html#jls-13.4.15 > <https://docs.oracle.com/javase/specs/jls/se7/html/jls-13.html#jls-13.4.15>. > Changing the return type is the equivalent of deleting the old method and > adding a new method. So it is in fact a binary incompatible change: A major > change (method delete). > -- > > BJ Hargrave > Senior Technical Staff Member, IBM // office: +1 386 848 1781 > OSGi Fellow and CTO of the OSGi Alliance // mobile: +1 386 848 3788 > hargr...@us.ibm.com > > > ----- Original message ----- > From: Robert Munteanu <robert.munte...@gmail.com> > Sent by: osgi-dev-boun...@mail.osgi.org > To: OSGi Developer Mail List <osgi-dev@mail.osgi.org> > Cc: > Subject: Re: [osgi-dev] Different conceptual version numbers for different > forms of backwards compatibility? > Date: Thu, May 4, 2017 5:40 AM > > Hi Simon, > > On Wed, May 3, 2017 at 10:46 PM, Simon Spero <sesunc...@gmail.com> wrote: > > I'm trying to clarify some thoughts in my own mind about how different kinds > > of backwards compatibility interact with different kinds of version > > numbering. > > > > There are at least two dimensions of backwards compatibility of relevance: > > binary v. source, and provider v. consumer. Not all combinations are > > important to OSGI , but there do to seem to be some situations where > > different use types suggest different potential version numbers (rather than > > ranges). > > > > 1. Source compatible but binary incompatible changes. > > In Java, the most commonly discussed changes of this kind are specializing > > a method return types (e.g. Collection<String> => List<String>). I > > > > Under standard Java linkage rules, this will cause the methods to have > > different signatures, making them incompatible, and requiring a major > > version change. > > Not to detract from your main point, but method return types are not > part of the method's signature in Java. > > https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.4.2 > <https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.4.2> > > Robert > > > > > Older source can be compiled against the newer library without changes, > > either to the source code, or a hypothetical range of return specialized > > (RS) versions ; if the source were changed to use the more specialized > > return type, it would require the increasing the minimum RS version > > number. Thus, only a minor RS bump is required. > > > > Where this becomes interesting is if an OSGI framework is extended to be > > able to rewrite calls from older bundles to use the newer method signature > > (quasi-recompiling). That would allow the newer package to satisfy more > > constraints. > > > > 2. Provider vs. Consumer : default methods > > > > One of the primary use cases for default methods is to allow for new methods > > to be added to interfaces without requiring changes to existing providers. > > These might be convenience methods, be optional with reasonable defaults, or > > be implementable using existing methods, with more performant > > implementations possible but not mandatory. > > > > Early experiments handling default methods in OSGI using micro versions > > showed that that approach was not viable. > > > > A different approach might be to consider changes that only add default > > methods to be neutral to invisible to an implementation of the previous > > version of the class (excluding accidental signature clash). > > > > To packages calling the new methods there has been a minor increase; > > similarly for packages that implement one or more of the default methods. > > > > It seems to me as if there is a separate conceptual version number is > > default aware, and that need not have the minor bump required in the > > primary version number. > > > > [I'm getting ready to run analysis over a mostly complete set of all bundles > > in the index on the ibiblio maven central mirror, which is mostly complete > > through 11/2016, where a bundle is defined to be any artifact that had a BSN > > in the manifest when processed by the nexus (now maven) indexer. I may > > augment this set with output of any PAX wrap: URLs mentioned in Karaf > > feature files. > > > > Some of my primary hypotheses is that the majority of these bundles do not > > follow semantic versioning rules, and that some, but not all, of the set of > > importing bundleswill have detectable possible linkage errors (e.g a > > reference to a removed class or method). > > > > A secondary hypotheses is that applying recommended bndlib Baseline > > renumbering to all (non qualified?) versions in a sequence, mapping > > external referencing import ranges to the appropriate rebased range will > > result in a non-trivial set of unsatisfiable dependencies. > > > > There are other hypotheses that I'm trying to refine; what I'm hoping to > > find are indica that can be used to predict more reliable import ranges for > > given maven artifact sequences, and to identify opportunities for safely > > relaxing constraints.] > > > > Simon > > > > > > > > > > > > _______________________________________________ > > OSGi Developer Mail List > > osgi-dev@mail.osgi.org > > https://mail.osgi.org/mailman/listinfo/osgi-dev > > <https://mail.osgi.org/mailman/listinfo/osgi-dev> > > > > -- > http://robert.muntea.nu <http://robert.muntea.nu/>/ > _______________________________________________ > OSGi Developer Mail List > osgi-dev@mail.osgi.org > https://mail.osgi.org/mailman/listinfo/osgi-dev > <https://mail.osgi.org/mailman/listinfo/osgi-dev> > > > > _______________________________________________ > OSGi Developer Mail List > osgi-dev@mail.osgi.org > https://mail.osgi.org/mailman/listinfo/osgi-dev
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