Bug#574380: edos-distcheck: Wrong output for | alternative?

[Stefano Zacchiroli <zack@debian.org>]

tags 574380 + patch
thanks

On Fri, Mar 19, 2010 at 09:58:44AM +0100, Stefano Zacchiroli wrote:
> > Dropping a build-dependency on a build-essential package is of course
> > only correct when
> > - and if it occurs as element of a conjunction, not as element of a
> >   disjunction: true and x is equivalent to x, but true or x is not
> >   equivalent to x.
> This point if of course correct, I'll fix add-sources.py to properly
> cover that (in a few days though, I'll be traveling between today and
> tomorrow).

Here I am, please find attached a patch for this.

Essentially, the flaw was that before the build-essential check was
mixed with checking whether a given build-dep was "for us"
(i.e. declared on the current architecture) or not. I've now split the
two tests: if a given disjunctive build-dep now contains a "trivial
dependency", it is dropped all together. A dependency is trivial
according to the above criteria (it is on a build-essential package and
it is not versioned).

Note that currently the check on the version of the build-dep is merely
syntactical for the recurrent problem that we don't know which versions
of the build-essential packages are installed. This might "save" from
erasure more build-essential-dep than needed (and surely more than
before, when the version was not taken into account).

Please comment now on this if you consider it non appropriate.

> The third possibility is for now to just fix properly the "OR
> optimization" as I said above. It looks like it will fix _this_ specific
> case, but can of course fail in other/weirded cases.

I've tested this on the example given by Kurt and the OR-ed dep is now
correctly preserved. As I'm offline, I can't do more tests right now,
any taker? :-)

Cheers.

PS the attached patch is _not_ cumulative with the previously posted one
   for the unicode issue

-- 
Stefano Zacchiroli -o- PhD in Computer Science \ PostDoc @ Univ. Paris 7
zack@{upsilon.cc,pps.jussieu.fr,debian.org} -<>- http://upsilon.cc/zack/
Dietro un grande uomo c'è ..|  .  |. Et ne m'en veux pas si je te tutoie
sempre uno zaino ...........| ..: |.... Je dis tu à tous ceux que j'aime

--- add-sources.py.orig	2010-03-24 20:51:27.000000000 +0100
+++ add-sources.py	2010-03-24 20:50:58.000000000 +0100
@@ -47,9 +47,7 @@
 
     def dep_for_me(dep):
         for_me = None
-        if buildessentials.count(dep['name']) > 0:
-            for_me = False
-        elif dep['arch'] is None:
+        if dep['arch'] is None:
             for_me = True
         elif dep['arch']:
             (polarity, _) = dep['arch'][0]
@@ -73,12 +71,23 @@
                     rels.extend(relations[name])
             return rels
 
+        def is_trivial_dep(or_deps):
+            """checks whether a given disjunction is trivially satisfiable,
+            e.g. because it contains an unversioned build-essential dependency
+            """
+            for dep in or_deps:
+                if dep['name'] in buildessentials \
+                        and not (dep.has_key('version') and dep['version']):
+                    return True	# unversioned build-dep on a build-essential
+            return False
+
         src_rels = get_rels(fields, relations)
         bin_rels = []
         for or_deps in src_rels:
-            my_or_deps = map(strip_arch, filter(dep_for_me, or_deps))
-            if my_or_deps:
-                bin_rels.append(my_or_deps)
+            if not is_trivial_dep(or_deps):
+                my_or_deps = map(strip_arch, filter(dep_for_me, or_deps))
+                if my_or_deps:
+                    bin_rels.append(my_or_deps)
 
         return bin_rels