This commit adds two checks to the validation phase of the solver:

1. It checks that each newly chosen package instance contains all executables
   that are required from that package so far.

2. It checks that each new build tool dependency that refers to a previously
   chosen package can be satisfied by the executables in that package.

This commit also fixes a TODO related to solver log messages. Previously, it was
possible for the log to associate an incorrect executable name with a
dependency.

This commit changes the field of type 'IsExe' in the 'Dep' data type to
type 'Maybe UnqualComponentName'.  It also adds the executable name to error
messages that previously just contained "(exe)".

This commit splits the 'Conflicting' constructor of 'FailReason' into five
different constructors, for different types of dependency conflicts.  This
change makes it easier to print different error messages for different
conflicts, though it doesn't change any of the error messages yet.

The refactoring caused a small change to the error message for conflicts caused
by self-dependencies.

Fixing the TODO caused the solver to report conflicting constraints in the
opposite order in some cases, but the change didn't seem to have a negative
impact on the clarity of the error messages.

Here is an example of the change from running
"cabal install --dry-run nerf --index-state=2017-11-04T18:36:30Z -v3":

 [_19] trying: template-haskell-2.11.1.0/installed-2.1... (dependency of tagged)
 [_20] next goal: pretty (dependency of template-haskell)
-[_20] rejecting: pretty-1.1.3.3/installed-1.1... (conflict: pretty => deepseq==1.4.2.0/installed-1.4..., text => deepseq>=1.1.0.0 && <1.4)
+[_20] rejecting: pretty-1.1.3.3/installed-1.1... (conflict: text => deepseq>=1.1.0.0 && <1.4, pretty => deepseq==1.4.2.0/installed-1.4...)
 [_20] rejecting: pretty-1.1.3.5, pretty-1.1.3.4, pretty-1.1.3.3, pretty-1.1.3.2, pretty-1.1.3.1, pretty-1.1.2.1, pretty-1.1.2.0, pretty-1.1.1.3, pretty-1.1.1.2, pretty-1.1.1.1, pretty-1.1.1.0, pretty-1.1.0.0, pretty-1.0.1.2, pretty-1.0.1.1, pretty-1.0.1.0, pretty-1.0.0.0 (conflict: template-haskell => pretty==1.1.3.3/installed-1.1...)
 [_20] fail (backjumping, conflict set: pretty, template-haskell, text)

This reverts commit bdb51a36.

Herbert Valerio Riedel authored 7 years ago and Mikhail Glushenkov committed 7 years ago

(cherry picked from commit 0a28ab6a)

Version range refactor

Add s/cmm-sources + extra-bundled-libraries

Apply 'any' qualifier to new-freeze constraints (fixes #4832).

Adds defaultMainWithHooksNoReadArgs

'makeAbsolute' is not compatible with old versions of 'directory' and
we know at this place in the code that the directory we refer to does
exist, so the potential exception is not a problem.

Fixes #4606.

(cherry picked from commit 560903cf)

Not absolutely happy with this solution. I fail to come up with a better one though.
The issue is that for some libraries, you might want to have _debug, _p, _l, as well as _thr_debug, _thr_p, _thr_l flavours.

# Conflicts:
#	Cabal/Distribution/PackageDescription/Parsec/FieldDescr.hs

# Conflicts:
#	Cabal/Distribution/PackageDescription/Check.hs
#	Cabal/Distribution/PackageDescription/Parsec/FieldDescr.hs
#	Cabal/Distribution/Parsec/Types/FieldDescr.hs
#	Cabal/doc/developing-packages.rst

new-install: nonlocal exes

[ci skip]

RFC: Relax coding guideline regarding module imports

This is a refactoring abstracting `FlagAssignment` while retaining its
external appearance as much as possible (i.e. same Read/Show/Binary
instances etc).

Later we can attach new instances, enforce internal invariants (like
e.g. uniqueness of flagnames), switch out the internal
representation (maybe to `Data.Map`), etc more easily.

Implement native DNS hackage-security bootstrap via resolv/windns packages

I notice imports like

    import qualified Text.PrettyPrint as Disp
          ( Doc, render, char, text )

which seem overly precise to me, when `Disp.` is only used
locally as a module prefix, and there's no other imports sharing
the same module prefix.

Instead, it should suffice to either use

    import qualified Text.PrettyPrint as Disp

or

    import Text.PrettyPrint
          ( Doc, render, char, text )

or in rare cases even

    import Text.PrettyPrint as Disp
          ( Doc, render, char, text )

Hence this relaxes the coding guidelines to allow these simpler forms
to be used.

[skip ci]

...via the new @windns@ package (which provides a compatible subset
of the @resolv@ API)

The flag is renamed from `resolv` to `native-dns`

This avoids calling out to an external `nslookup` program and having
to screen scrape its output. The `resolv` library supports all
platforms which provide the ubiquitous `libresolv` API.

This is hidden behind the manual cabal flag `resolv` which is
currently disabled by default.

RFC: Potential fix for #4808