How to fix arnesi:clean-op.

[Robert Goldman]

I am inclined to agree with Andreas.  I don't see that CLEAN-OP is
impossible for ASDF.  I can see that there are some issues that require
thought, and for some systems additional coding by the developer, but I
don't see that as an insuperable barrier.  After all, "make clean" is in
some sense impossible (it's generally hand-coded by the programmer), but
we use it every day.
I accept Faré's points about there being challenges to write an ideal
CLEAN-OP.  But I don't agree that this means that we can't write a good
enough CLEAN-OP. After all, make manages "make clean."  Yes, it requires
some effort from the programmer, but who cares?  Is that a reason we
have to throw up our hands and refuse to do anything?  Here are some
specific responses to particular issues.

On the other hand, while I don't agree that these make the CLEAN-OP
impossible, I *do* agree that they are difficult issues. So... I'd be
happy to see CLEAN-OP added, and I'd be happy to support this effort,
*BUT* CLEAN-OP patches must be preceded -- by an informal specification
that describes what an implementation should do, covering these cases.

Now that ASDF is on everyone's critical path, we need to think a little
before changing it, and not just bash out a hunk of code.


Specific responses to Faré's issues:

1. clean-op is not defined in general.  I believe that this means "do we
clean the system" or "do we clean the operation" [as in arnesi, whose
CLEAN-OP has a FOR-OP]?

This seems similar to the notion that Faré already had, of providing a
BUILD-OP that does "the default build action" for a system (e.g., maybe
it builds the library?  Maybe it does LOAD-OP? Maybe it does LOAD-OP and
DOC-OP?).

So one solution would be to have an UNMAKE-OP that does the inverse of
the build-op, and then have a CLEAN-OP that undoes specific operations
(like the arnesi CLEAN-OP).  Then the UNMAKE-OP might default to being
the CLEAN-OP for COMPILE-OP, which would handle probably 90% of systems.

On the other hand, I'm pretty unhappy with the notion of the BUILD-OP,
because it requires retraining every single user of ASDF to use BUILD-OP
instead of LOAD-OP.  That would be an enormous user interface fail.  So
this is not a step to be taken lightly.


2. I think we can simply make clean-op clean for the current implementation.

3. I believe we should mirror the semantics of :FORCE T and :FORCE ALL
when we unmake.  I.e., unbuild the dependencies only with :FORCE :ALL.
:FORCE T would actually be a no-op.

4.  "How do you deal with
defsystem-depends-on and other dependencies not explicitly
included in the plan?"  DEFSYSTEM-DEPENDS-ON is already broken, and will
be deprecated, except as a checkable declaration (see earlier postings
on this list for a description of the issues).  For the rest, I'd say
same as above -- if there's something that won't appear in the build
plan that one needs to clean, then the programmer must write an
:IN-ORDER-TO for the CLEAN-OP so that ASDF can know what it needs to do.

5. "Are you sure there aren't bugs and
omissions in asdf or any extension whereby some side output file
is omitted from the list?"

ow does make deal with a file that isn't listed in the rule for "make
clean"?  You miss it.  Very sorry.  Fix your system definition.  Use
(:in-order-to (clean-op ....))

6. "What about randomly-named temporary
files created during an operation that has been interrupted?"  Maybe we
are doing the Wrong Thing with these.  If they are temporary files,
maybe it's the wrong thing to put them in the cache and rename them?
Maybe they should live in /tmp (or equivalent) and be moved from there?
Then it's not our problem to fix anymore -- that's for tmpwatch.

If you add your own rules that make temporary files, you have to add
your own rules that remove them.

7. "What if load-op is not the only operation that matters, but
e.g. doc-op generates LaTeX and PDF outputs but fails to be
tracked by clean-op? Are you going to use the CLOS MOP to
generate a list of all possible operations? What if that other
operation isn't loaded in the current image? What if operation
options cause different files to be generated? Or features? What
about all secondary systems? Are you going to generate a plan
for them, too?"

See the answer to #1:  ASDF is not going to solve this problem.  Either
the programmer solves it using definitions of PERFORM and IN-ORDER-TO,
or it's not solved. So sad.  But I don't see any reason to avoid the 90%
solution because there isn't a 100% solution.

Best,
r