GitLab

E.g. cabal install cabal-1.8.0.6 would actually install the latest version
instead, because when 'cabal' got corrected to 'Cabal' the associated
constraint 'cabal == 1.8.0.6' was not converted to 'Cabal == 1.8.0.6'.

Will make tracking down problems easier in future.

It is actually possible for pruning to eliminate required packages
because it's possible for it to propagate all the way up to one of
the initial targets.

e.g. --constraint='foo source'
     --constraint='baz installed'
     --constraint='bar +this -that'

Now log when things get excluded due to installed and source constraints.

There are many packages that can never be successfully configured
and by pruning them early we reduce the number of choices for the
solver later (which is good since the solver does no backtracking
when it makes bad choices). This relies on two recent features:
1. we can now express constraints that exclude a particular source
package and 2. that we can exclude packages without needing to know
whether or not they will ever be needed.

The constraint set ADT now needs to be told which targets we are
interested in, rather than assuming anything we constrain might
be a target.

We now track target packages and only require constraints on those
targets to be satisfiable. This allows us to overconstrain packages
that we do not care about, which is useful for excluding broken
packages.
We also now have a more general way of specifying constraints.
Previously constraints were specified as the conjunction of a version
range predicate and an optional installed constraint. This form made
it impossible to express constraints such as "exclude this source
package". Constraints for a package name are now specified simply by
a function predicate on the package version and installed/source state.

Rather than 'available' packages, the source now refers consistently to
'source' packages. This is a bit clearer.

Fixes ticket #810

I'd accidentally left out the world target from the parsing phase
of the new user target handling system, so cabal install world did
not work. Now added to the target parser.

I made a mistake during the recent refactoring work and was using
the dependency planner in the wrong way. The planner was being
given the available source packages and duely picking them to
satisfy dependencies, but for configure we're supposed to assume
that all dependencies are installed already.

Previously when multiple instances of the same package are installed,
e.g. in global and user dbs, we would often end up selecting the wrong
instance. Now we select the user one consistently which will solve the
problem in most (but not all) cases.

For several commands, including install the -v verbosity level had
far too much useless internall stuff in it. Reduced the amount of
output from configuring the compiler, getting installed package and
the dependency planner. The extra detail is still available via -v3.

No longer needed now that the world target is handled via UserTarget.

Also minor tweak to InstallPlan.remove

Helps to clarify things now that different kinds of packages
are fetched in different ways.

Allows shorter and clearer code for the various ways the resolver is used.

The new user target system requires a change in how cabal info works.
Instead of just giving package names and looking them up in the
available package index, we can now specify names with versions or
version constraints which means we want the info to be about that
version in particular. We now list many installed and available
versions and mark which ones are preferred or not. Also fix a bug
for packages that are only installed, not available.

This will allow us to increase the range of targets that cabal
commands can support. The new ones are local directory targets,
local cabal files, local tarballs and remote tarballs by URL.
Also a better way of doing the special "world" target.

Works for any package identified by PackageLocation
rather than just for repo packages.

So we can now use PackageLocation FilePath or Maybe FilePath to
describe what we know about the fetch status of package tarballs.

Currently just a renamed copy of UnresolvedDependency but called
WorldPkgInfo and defined in the World module. This is in preparation
to remove all other uses of the UnresolvedDependency type.

And remove import list for Types module, just import it all