[asdf-devel] New features in ASDF 2.27

[Faré]

OK, so ASDF 2.27 has been 2 months in the doing, plus one month initial hyatus,
that's three months since 2.26. Since then it has a bit over doubled in size,
and the testing of it has caused a lot of breakage, for which I apologize again.

Here is a list of the major changes so far, glossing over buglet fixes
and internal changes that should be invisible to users:

  * ASDF-BUNDLE was merged into ASDF.
    This notably means fewer headaches for users of ECL;
    it also means a new load-fasl-op feature for all users of a modern CL,
    making it easier to deliver software as a single fasl.
    After release, I plan to offer a patch so SBCL use that for its contrib's.
    All remnants of asdf-bundle's predecessor asdf-ecl were removed.

  * *decades-old* bugs of notable significance were fixed:
    (a) changes in dependencies now trigger a rebuild across systems, and
    https://bugs.launchpad.net/asdf/+bug/479522
    (b) timestamps are now correctly propagated (they weren't at all!)
    https://bugs.launchpad.net/asdf/+bug/1087609
    In olden days, some have argued for not rebuilding systems that :depend-on
    a modified one as a "feature". It really isn't. On the other hand,
    it is now possible to explicitly prevent a system from being rebuilt, using
    an actual feature, :force-not, which was released in 2.21 in April 2012.
    Someday I will write about those bugs.

  * PREPARE-OP was introduced to fix a conceptual bug in the ASDF object model.
    It corresponds to "loading the dependencies of a component and its parents"
    and is explicitly depends-on'ed by LOAD-OP and COMPILE-OP of the component,
    instead of their implicitly depending on it via the TRAVERSE algorithm,
    which implicit dependency proved fatal in cases revealed by the above bugs.
    It propagates upward in the component hierarchy, rather than downward,
    like the TRAVERSE algorithm used to systematically propagate dependencies.

  * TRAVERSE was gutted out and factored into reusable higher-order functions
    and objects, which not only fixes the above conceptual bug, but makes for
    semantics that are simpler to implement, possible to understand,
    easier to extend, and less limited in expressivity.
    TRAVERSE doesn't automatically propagate operations
    downward the component hierarchy anymore;
    propagation is now implemented through methods on COMPONENT-DEPENDS-ON.

  * COMPONENT-DEPENDS-ON is now more powerful:
    it can express dependencies on arbitrary operation objects
    (i.e. operations of the same class can have different options)
    acting on arbitrary component objects
    (i.e. not necessarily siblings of the current component).
    The ASDF object model can now express arbitrary build graphs, with
    no more special magic for children components vs other dependencies.

  * COMPONENT-DO-FIRST is no more. It used to specify some dependencies
    that were skipped if no re-build was triggered based on local timestamps.
    Instead, COMPONENT-DEPENDS-ON is used for all dependencies,
    and all are consulted to correctly propagate timestamps.
    However actions meant for in-image side-effects are included
    only if needed, and might be visited twice by TRAVERSE,
    first without the needed-in-image-p flag, another time with.

  * FORCE and FORCE-NOT now correctly distinguish T from :ALL in addition to
    a list of system name specifiers, as per the original specification
    (which was never implemented in ASDF 1). Additionally,
    builtin systems (such as SB-BSD-SOCKETS on SBCL) cannot be forced
    (which doesn't work on SBCL).

  * IF-FEATURE is a new attribute of components that accepts an arbitrary
    feature expression such as (:and :sbcl (:or :x86 :x86-64)),
    which when defined is a precondition to the component being enabled;
    when the expression is false, the component is disabled,
    and dependencies to it are removed.
    It replaces the misguided :if-component-dep-fails attribute of modules
    and the accompanying :feature feature, which were dropped.
    They were not very expressive, clunky to use, and relied on baking
    conceptually dubious non-local behavior in the old TRAVERSE algorithm,
    which belied the object model and defeated other features.
    Unhappily, this breaks backwards compatibility for the few who used it,
    namely sb-grovel, nibbles and ironclad.
    A minimal compatibility layer allows ASDF 2.27 or later to load
    the SB-GROVEL of old versions of SBCL, but it won't suffice to load
    an old version of nibbles or ironclad; please upgrade them
    a recent version that was updated to support ASDF 2.27.

  * CONCATENATE-SOURCE-OP is a new operation that builds a single Lisp file
    from all the source files in a system,
    which allows you to develop in a structured way with many compact files,
    yet deliver a large single file. Other related operations allow you
    to load that source file, or compile and load it,
    or do the same while including all other system dependencies.
    ASDF was broken up into lots of small files, to be delivered that way.

  * FOO/BAR/BAZ names will be recognized by defsystem as having to be located
    in a file called foo.asd. This is backward compatible in the case where
    you somehow arranged to load foo.asd before to use the other subsystems,
    except now ASDF can find the subsystems by name without the main system
    definition having been loaded. See uses of function PRIMARY-SYSTEM-NAME.

  * BUILD-OP is a generic operation that can do the "right thing" for
    each system, without users having to maintain the knowledge of
    what the right thing is for each system they may indirectly depend on.

  * Convenience methods were added to most exported generic functions,
    so you can (input-files 'compile-op '(system1 "file1")) instead of
    (input-files (make-instance 'compile-op) (find-component 'system1 "file1"))
    This notably makes it much easier to interact with ASDF at the REPL
    and debug your system definitions or ASDF extensions (or modifications).

  * Packages were introduced as ASDF was broken up into small files.
    Each file now has its own package, importing and exporting functionality,
    following the style made popular by faslpath and quick-build.
    ASDF does not yet include builtin support for quick-build or faslpath
    systems and dependencies, however. Possibly in ASDF 2.28.

  * ASDF-DRIVER is a separately-usable library for Common Lisp runtime support.
    It is transcluded in asdf.lisp (i.e. when delivering ASDF as a separate
    bootstrap file, the contents of ASDF-DRIVER have been included in it),
    but can also be used as a separate ASDF system on top of an old ASDF
    (within limits: CLISP and XCL still need a recent ASDF).
    The package ASDF/DRIVER (with short nickname :D) re-exports
    all the functions that ASDF needed to run portably.

  * Pathnames are a notable part of ASDF-DRIVER, required to deal
    portably with pathnames despite the many bugs and variations
    from platform to platform. See notably in pathname.lisp,
    MERGE-PATHNAMES*, SUBPATHNAME, PARSE-UNIX-NAMESTRING,
    PARSE-NATIVE-NAMESTRING, ENSURE-PATHNAME, and many many more.

  * Pathname use by ASDF was also improved in countless small ways,
    closing more buglets that appeared in as many corner cases.
    For instance, system pathname defaulting was improved,
    and systems not associated with a file will now have NIL as their pathname,
    which will otherwise be correctly treated.
    Many things that would vary depending on implementation will work better.
    Also, although we cannot strongly enough disrecommend the use of so-called
    "logical pathnames", especially where portability matters in any way, we
    support them better than ever within the limitations of the implementation.

  * Image lifecycle support is included in ASDF-DRIVER (and thus ASDF);
    this standardizes things like access to *COMMAND-LINE-ARGUMENTS*,
    declaring an entry-point to a program, hook functions and/or a prelude
    to run before to start the main entry, and a postlude and/or hook functions
    to run before to dump an image, dumping or creating an image, etc.

  * PROGRAM-OP allows you to create standalone executables on implementations
    that support it: CLISP, Clozure CL, CMUCL ECL, LispWorks, SBCL, SCL.
    A hello-world-example system shows demonstrates how to use it.

  * Run-program is a replacement for the old run-shell-command.
    Unlike run-shell-command, it is portable to Windows as well as Unix,
    it can avoid going through a shell and will sensibly escape arguments
    when it does go through a shell, and it has a usable interface
    to either capture program output or run the program interactively.
    This supersedes run-program/ previously available from xcvb-driver,
    including several improvements and portability fixes.

  * Conditions can be selectively muffled around compilation thanks to
    the an around-compile hook and the *UNINTERESTING-COMPILER-CONDITIONS*
    parameter, and around loading with *UNINTERESTING-LOADER-CONDITIONS*
    which is _appended_ to the former during loading.
    This supersedes the functionality previously available from xcvb-driver
    and its thin wrapper asdf-condition-control, which was retired.

  * Deferred warnings for yet undefined functions, that in a single-session
    build are usually signaled at the end of a compilation unit, will be
    saved and reassembled to make each system a compilation unit of its own,
    even when compilation of file happens across multiple sessions;
    only CCL and SBCL support this feature at this time.
    I welcome patches for other compilers, for which ASDF will _not_
    wrap an implicit WITH-COMPILATION-UNIT around its operate method anymore.

  * COMPILE-FILE* was beefed up to support all these features and more,
    and the Right Thing(tm) on all implementations, including
    support for their various extensions.

  * Internals have been refactored, and some sorry features were excised.
    The semantics of OPERATION-DONE-P is simplified and now well-specified.
    FIND-COMPONENT will pass component objects through, and
    a corresponding FIND-OPERATION replaces MAKE-SUB-OPERATION.
    Many internal accessors were renamed, after checking on Quicklisp
    that no one was using them.

  * Portability updates were done for
    ABCL, CLISP, Clozure CL, CMUCL, ECL, LispWorks Personal Edition, MKCL, XCL.
    Working support for GCL 2.6 was restored, with notable limitations
    including lack of support for output-translations or logical-pathnames.

  * TRUENAME resolution can be reliably turned off in all cases where
    ASDF was using them by setting the variable *RESOLVE-SYMLINKS* to NIL.
    This is useful if your operating system makes that operation slow,
    or if your build system uses symlinks to content-addressed storage
    in which case TRUENAME just does the wrong thing.

  * VERSION strings can now be specified as having to be fetched
    from a file using a (:read-file-form <path>) specification,
    that can use an optional :at keyword argument to specify
    a form or subform other than the first form in the file,
    as per the utility asdf-driver:access-at. For instance,
    if your file specials.lisp is a defpackage, an in-package
    and a defparameter of the version, then you could use:
	(:read-file-form "specials.lisp" :at (2 2))
    This makes it easier for developers to manage versioning
    of one or multiple systems with a single master version location.

  * Self-Upgrade of ASDF will happen automatically as the first thing
    before any attempt to build anything, as it was determined that
    doing it in the midst of a build breaks everything, and it is not
    otherwise possible to reliably detect in advance whether ASDF may
    be needed in such midst. If you don't want an ASDF upgrade, just
    don't configure your source-registry to include any copy of ASDF.

  * DEFINE-PACKAGE is provided as a replacement to DEFPACKAGE that supports
    hot upgrade of software where some packages have changed.
    It also provides new forms :MIX and :REEXPORT which can be quite practical.

  * ASDF2.27 was added to the *features* so you can detect the presence of
    this massively updated ASDF and its new features with #+asdf2.27.
    This is *not* ASDF3, for we painfully maintained backwards compatibility,
    though it may have been temporarily broken during development.

  * Documentation received some updates.

  * Tests were updated, notably including support for bundles, encodings,
    run-program, and more. They were successfully run on
	ccl clisp sbcl ecl ecl_bytecodes
	cmucl abcl scl allegro lispworks allegromodern xcl
    Manual tests were run on gcl2.6 genera lispworks-personal-edition.
    Untested remain cormancl mkcl rmcl.

  * ASDF-DEBUG is a simple utility to make your favorite debugging primitives
    available in the package you're debugging. See contrib/debug.lisp
    and the asdf/utility:*asdf-debug-utility* variable.

  * ASDF-UTILS is now but an empty shell that depends-on ASDF-DRIVER.
    The ASDF-DRIVER package has the ASDF-UTILS nickname, and exports
    all the functionality that used to be in ASDF-UTILS, and much more,
    minus a few misdesigned things from ASDF1 that you ought not
    to have been using, and for which there are non-broken replacements.
    ASDF-UTILS was distributed separately from ASDF; ASDF-DRIVER is available
    both as part of ASDF 2.27 and later and separately.

  * POIU was updated. This extension is still distributed separately from ASDF.
    It is now much simplified and made correct by construction by
    reusing the new TRAVERSE infrastructure of ASDF and now being able to
    assume the ASDF object model is a complete description of dependencies.
    On SBCL it will handle deferred warnings from background compilations.
    Where forking is not possible or not supported,
    it will gracefully fall back to serial compilation.

  * INFERIOR-SHELL (distributed separately) was updated to use asdf-driver
    instead of xcvb-driver, providing a richer interface to
    the RUN-PROGRAM functionality.

  * SLIME support for ASDF was significantly enhanced.
    It is distributed with SLIME, separately from ASDF.
    See latest slime checkin from 2013-01-20.
    We recommend that you should include slime-asdf in your slime-setup
    and that in your ~/.swank.lisp you should include:
    (in-package :swank)
    (pushnew 'try-compile-file-with-asdf *compile-file-for-emacs-hook*)
    This requires ASDF 2.014.6 or later (as used by older quicklisp releases).

There's one more feature pending, courtesy of Stelian Ionescu, that will
hopefully make it to the release that I hope will happen next week.

In the meantime, I welcome all testing of the new ASDF and/or its ASDF-DRIVER.

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org
Memory is like an orgasm... it's better when you dont have to fake it.
	— Seymour Cray