Hi!<br><br>Approximately after the release of ASDF 2 I've got interested in creating yet another system distribution management system on top of ASDF, and that made me investigate ASDF internals. Through that investigation, I've understood 2 things:<br>
* ASDF has support for much more, than is well known and in ordinary use by most Common Lisp programmers :)<br>* still it's support for versioning (which is essential to distribution management) is lacking due to:<br>
- possibility to specify only exact version<br> - somewhere in the depths of code version checking is lost (for example, there's no condition signaled, if in the process of system definitions traversal we load ASD file with different version for some system, that was already loaded, which actually causes errors in some situations, i.e. its a bug)<br>
- the syntax is not very friendly<br><br>So, during last month I was developing ASDF in the direction of more robust version support. I've started with 2.000, but fortunately there's no intersection between my work and recent developments up to version 2.106 (except for new DEFGENERIC*, which is trivial).<br>
<br>Attached is the proposed patch to ASDF, that, in my view, solves the aforementioned versioning problems. It does the following:<br>* Unifies internal version representation format in the form of a list of integers: (for example, ASDF 2.106 will have an internal version of '(2 106 0), while ASDF 2.005 — '(2 5 0)). At the same time, the users are given quite a lot of freedom in specifying versions, for example they can do that as before in string form (like "1.2.3"), so it's backwards compatible. This new format is more programming-friendly and several utility functions are added: PROPER-VERSION (to transform to it), V> (version-greater-or-equal), MAJOR-VERSION and MINOR-VERSION,— while VERSION-SATISFIES is much improved in the manner, that is explained below. Also a method for SLOT-UNBOUND is added to VERSION slot on a SYSTEM class, to return version '(0 0 0), which is considered (on par with NIL) to be a wildcard version spec, so to say.<br>
* Adds VERSION-P (version-predicate) parameter to different ASDF functions, that need to deal with versions. This specifies in which way to match versions with VERSION-SATISFIES and currently has the following variants: :EXACT (nil also translates to :EXACT), :ABOVE, :MAJOR+, :MINOR+, and also a second version spec, which means that version should be in the interval from the given version to version-p itself. This is the change, that I had had in mind, when I started looking at ASDF<br>
* Adds a continuable error of type SYSTEM-VERSION-CONFLICT, when we try to read ASD file with a different version of some system, that is already in memory<br>* Adds new format of version specification in :DEPENDS-ON clause of DEFSYSTEM. Besided (:version <system> <version>), which is retained and extended with version-p, i.e. (:version <system> <version> <version-p>) — example: (:version :hunchentoot "1.2.3" :above) ,— there's now also a simpler (<system> <version> <version-p>) — example: (:hunchentoot "1.2.3" :above)<br>
<br>A final note about versioning: I needed to use pre-reading of ASD files in order to know their versions without arising version conflicts. This works, except for the fact, that READ-EVAL is turned off in the process, so such version specifiers as: <br>
* :version #.*hunchentoot-version*<br>* :version #.(with-open-file (vers (merge-pathnames "version.lisp-expr" *load-truename*)) (read vers))<br>do not produce expected results and are treated as empty versions. There will be a need to make a note about that to library developers.<br>
<br>Besides, an incompatible change is introduced to FIND-SYSTEM. The ERROR-P optional argument is removed, so plain NIL is unconditionally returned, when system is not found, and VERSION and VERSION-P optional arguments are added instead.<br>
I'd like to argue, that this is justified by two things:<br>* there's no substantial use of ERROR-P argument neither in ASDF itself, nor anywhere in dependent code (at least I can tell that after a brief look at google search results)<br>
* more importantly, although there's another option to add version/version-p: add VERSION and VERSION-P as keyword arguments and leave ERROR-P also as keyword argument — I don't think, that overall the use of such argument is a proper architectural decision, because it's not an error actually, when system is not found — it's a common situation and should be dealt with in the caller appropriately to the context<br>
<br>My last note concerning this patch is about testing. After syncing with the development branch of ASDF, I see the addition of TEST directory. When I'd started my experiments, I had somehow missed it (or it had not been there?). Anyway, I have supplied a number of unit tests to the functions, that I have added. This is done with a very simple unit testing library of my own (a microframework so to say) MUTEST, that can be found at: <a href="http://github.com/vseloved/mutest/">http://github.com/vseloved/mutest/</a>. The tests are specified right in the code side-by-side with functions definitions, but are protected with #+mutest guards, so effectively can be ignored. They also have the benefit of showing, how each of the functions can be called. There's also a dummy directory structure under TEST, that is used in the tests and should be reproduced in the same directory, where ASDF-VERSION.LISP is located.<br>
<br>I have also done functional testing of the changes with the systems, that I have got installed already (around 70 libraries), and have verified, that there are no problems. At the same time I would not claim, that there will not be any problems with some system definitions, that use obscure ASDF features (although, I have acquainted myself with ASDF to the point, that I quite well understand most of the features as well as internals now). So I ask anyone interested in this set of changes to thoroughly test them.<br>
<br>At the same time I'd be glad to know more about utilizing the current ASDF test-suite.<br><br>Finally, the patch can be applied by simply loading ASDF-VERSION.LISP on top of the loaded ASDF 2.106.<br><br>I hope, this work proves useful and is integrated into ASDF. Anyway I'm willing to answer any questions and/or improve the implementation, if needed.<br>
<br>Vsevolod Dyomkin<br>