Add new 'user-config' subcommand 'init'.

Tomas Vestelind authored 9 years ago and Mikhail Glushenkov committed 9 years ago

'cabal user-config init' creates a default config file if it doesn't already
exist.

If '--config-file' is set, then that file will be written.

If '-f' or '--force' is used, then the file will be overwritten if it already
exists.

See https://github.com/haskell/cabal/issues/3003#issuecomment-176494768.

Solver feature: soft prefs for enabling testsuites/benchmarks

The solver has the concept of hard constraints and soft preferences.
For versions we have both constraints and preferences. We also have
soft preferences available for whether we'd like installed instanes
or not.

We also have hard constraints for enabling "optional stanzas" (ie test
suites or benchmarks). This patch adds soft preferences for the same.
That is it lets us express the desire to please try enabling test suites
and/or benchmarks, but allow them to be disabled if a solution cannot
easily be found with them enabled.

The implementation is very straightforward and not at all scary. :-)
The original design was discussed with kosmikus and it has seen
extensive testing in the nix-local-build branch.

Optional stanzas in the solver are treated very much like flags, and so
we can follow the pattern of a similar feature for flags for this
feature for optional stanzas. For both flags and optional stanzas the
solver has a node with up to two choices: True & False, corresponding to
enable and disable. Various policies can be expressed by reordering
these two choices or replacing one or other branch with failure. For
example we can force enabling by replacing the False choice with
failure. Flag default values are implemented by reordering the True and
False branches (since the solver will try the first branch first).

So this preference is implemented simply by reordering to put the True
branch first (keeping both branches). That way the solver will try the
enable branch first and backtrack to the False branch (which imposes no
constraints). It integrates smoothly with stanza constraints, which
adjusts the False branch to be a failure, thereby forcing the True
branch (or further failure).

The top down solver is simply adjusted for the types, the feature is not
implemented there.

The feature is not yet used. It's not intended to have any command line
flag, but to express future policies.

Refactor #3082 to reduce code duplication and improve Haddock comment.

Improve algorithm for choosing flags with './Setup configure'

Misc nix-local-build preparation patches

Cabal < 1.12.0 doesn't know about '--enable/disable-executable-dynamic'
or '--enable/disable-library-coverage'.

This is a problem in general, if rare, but it shows up in the
nix-local-build branch more obviously since it always passes all flags,
including defaults (it does this because the defaults should be
determined by the current version, not the older version).

Make the basic dependencyGraph construction function give us just a
Vertex -> UnitId mapping, rather than a full Vertex -> pkg. Then in
InstallPlan we keep that Vertex -> UnitId mapping and add a helper
function that does the additional lookup to give us a Vertex -> pkg
mapping. It's clearer this way, especially in the case of lookup errors.

This is easier to understand now that the canonical data vs the cached
graph is clarified. We only store the main data, the cached info is
reconstructed on deserialisation.

This is to clarify the lazy caching strategy we use for the fields for
the Graph (forward and reverse deps, and associated mappings).
Reorder the fields, and mark non-lazy fields as strict. Make
construction go via a smart constructor that fills in the cached fields.

Useful for reporting dir/file names in user interface code, e.g. in
notices and error messages.

Required by later nix-local-build branch patches.

Required by later nix-local-build branch patches.

Add Binary instances for many types

So we can use them in binary cache files.

Also relax version constraints on binary to work with binary-0.5.*,
which requires that we expose Distribution.Compat.Binary from Cabal.

D.Compat.Binary provides the Gerics support that we need to be able to
derive instances when using binary-0.5. It's useful to be able to use
binary-0.5 since that's the version bundled with older ghc versions.

remove duplicate LANGUAGE DeriveFoldable, minor improvements

Cabal previously tried all flag combinations, which was very slow.  The new
algorithm assigns one flag at a time, and backtracks when a flag introduces a
dependency that is unavailable.

The new algorithm handles the Buildable field by adding an extra conditional at
the top level of each component that represents the condition for which the
component is buildable.  Since all dependencies go under the "then" branch, they
are only required when a flag choice makes the component buildable.  The buildable
logic is taken from the cabal-install dependency solver.

This commit also changes the error message that is shown when dependencies are
missing.  Previously, Cabal printed the shortest list of missing dependencies
from a single flag assignment.  Now it takes the union of all dependencies that
caused it to backtrack when trying different combinations of flags, which
requires less searching.

Fix space leak in ./Setup configure

redundant map after fold

See https://github.com/haskell/cabal/issues/3003#issuecomment-174492371

It uses 'build-type: Simple' now.