The new Installability Tester (IT) module replaces the remaining
C-parts. Unlike C-implementation, it does not give up and emit an
"AIEEE" half-way through.
In order to determine installability, it uses two sets "musts" and
"never". As the names suggest, the sets represents the packages that
must be (co-)installable with the package being tested and those that
can never be co-installable. For a package to be installable, "musts"
and "never" have remain disjoint.
These sets are also used to reduce the number of alternatives that are
available to satisfy a given dependency. When these sets are unable
to remove the choice completely, the new IT defers the choice to later.
This occasionally reduces backtracking as a later package may conflict
or unconditionally depend on one of the remaining alternatives.
Signed-off-by: Niels Thykier <niels@thykier.net>
As HintItem is now redundant, also replace it with a new class -
UnversionnedMigrationItem - and migrate users of the classes to use
the new versions.
Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>
This function allows a textual representation of a package (e.g.
"foo/amd64") to be convered to a HintItem().
Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>
Where possible, avoid creating a list only to discard immediately
afterwards. Example:
"""
for x in sorted([x for x in ...]):
...
"""
Creates a list, passes it to sorted, which generates a new list and
sorts that copy. Since sorted accepts an iterable, we can avoid the
"inner" list and just pass it a generator expression instead.
Signed-off-by: Niels Thykier <niels@thykier.net>
By moving the package loop inside register_reverses, it will be
invoked a lot less (reducing the overhead of invoking functions).
Signed-off-by: Niels Thykier <niels@thykier.net>
Niels Thykier
Adam D. Barratt