Commit 0b1e55f9 authored by Simon Marlow's avatar Simon Marlow

Allow -package-id to override the default package shadowing semantics

So that Cabal, if it wants, can use a more general algorithm to find a
consistent set of packages to use.
parent 4eccf57c
......@@ -127,6 +127,8 @@ type PackageConfigMap = UniqFM PackageConfig
type InstalledPackageIdMap = FiniteMap InstalledPackageId PackageId
type InstalledPackageIndex = FiniteMap InstalledPackageId PackageConfig
emptyPackageConfigMap :: PackageConfigMap
emptyPackageConfigMap = emptyUFM
......@@ -533,7 +535,7 @@ findBroken pkgs = go [] emptyFM pkgs
where new_ipids = addListToFM ipids
[ (installedPackageId p, p) | p <- new_avail ]
depsAvailable :: FiniteMap InstalledPackageId PackageConfig
depsAvailable :: InstalledPackageIndex
-> PackageConfig
-> Either PackageConfig (PackageConfig, [InstalledPackageId])
depsAvailable ipids pkg
......@@ -545,21 +547,27 @@ findBroken pkgs = go [] emptyFM pkgs
-- Eliminate shadowed packages, giving the user some feedback
-- later packages in the list should shadow earlier ones with the same
-- package name/version.
shadowPackages :: [PackageConfig] -> UnusablePackages
shadowPackages pkgs
= let (_,shadowed) = foldl check (emptyUFM,[]) pkgs
-- package name/version. Additionally, a package may be preferred if
-- it is in the transitive closure of packages selected using -package-id
-- flags.
shadowPackages :: [PackageConfig] -> [InstalledPackageId] -> UnusablePackages
shadowPackages pkgs preferred
= let (shadowed,_) = foldl check ([],emptyUFM) pkgs
in listToFM shadowed
check (pkgmap,shadowed) pkg
= (addToUFM pkgmap (packageConfigId pkg) pkg, shadowed')
check (shadowed,pkgmap) pkg
| Just oldpkg <- lookupUFM pkgmap (packageConfigId pkg)
= (installedPackageId oldpkg, ShadowedBy (installedPackageId pkg))
= let
ipid_new = installedPackageId pkg
ipid_old = installedPackageId oldpkg
if ipid_old `elem` preferred
then ( (ipid_new, ShadowedBy ipid_old) : shadowed, pkgmap )
else ( (ipid_old, ShadowedBy ipid_new) : shadowed, pkgmap' )
| otherwise
= shadowed
= (shadowed, pkgmap')
pkgmap' = addToUFM pkgmap (packageConfigId pkg) pkg
-- -----------------------------------------------------------------------------
......@@ -575,6 +583,20 @@ ignorePackages flags pkgs = listToFM (concatMap doit flags)
-- a preventative measure just in case P exists.
doit _ = panic "ignorePackages"
-- -----------------------------------------------------------------------------
depClosure :: InstalledPackageIndex
-> [InstalledPackageId]
-> [InstalledPackageId]
depClosure index ipids = closure emptyFM ipids
closure set [] = keysFM set
closure set (ipid : ipids)
| ipid `elemFM` set = closure set ipids
| Just p <- lookupFM index ipid = closure (addToFM set ipid p)
(depends p ++ ipids)
| otherwise = closure set ipids
-- -----------------------------------------------------------------------------
-- When all the command-line options are in, we can process our package
-- settings and populate the package state.
......@@ -592,13 +614,58 @@ mkPackageState
mkPackageState dflags pkgs0 preload0 this_package = do
1. P = transitive closure of packages selected by -package-id
2. Apply shadowing. When there are multiple packages with the same
* if one is in P, use that one
* otherwise, use the one highest in the package stack
rationale: we cannot use two packages with the same sourcePackageId
in the same program, because sourcePackageId is the symbol prefix.
Hence we must select a consistent set of packages to use. We have
a default algorithm for doing this: packages higher in the stack
shadow those lower down. This default algorithm can be overriden
by giving explicit -package-id flags; then we have to take these
preferences into account when selecting which other packages are
made available.
Our simple algorithm throws away some solutions: there may be other
consistent sets that would satisfy the -package flags, but it's
not GHC's job to be doing constraint solving.
3. remove packages selected by -ignore-package
4. remove any packages with missing dependencies, or mutually recursive
5. report (with -v) any packages that were removed by steps 2-4
6. apply flags to set exposed/hidden on the resulting packages
- if any flag refers to a package which was removed by 2-4, then
we can give an error message explaining why
7. hide any packages which are superseded by later exposed packages
flags = reverse (packageFlags dflags)
ipid_map = listToFM [ (installedPackageId p, p) | p <- pkgs0 ]
ipid_selected = depClosure ipid_map [ InstalledPackageId i
| ExposePackageId i <- flags ]
(ignore_flags, other_flags) = partition is_ignore flags
is_ignore IgnorePackage{} = True
is_ignore _ = False
shadowed = shadowPackages pkgs0
shadowed = shadowPackages pkgs0 ipid_selected
ignored = ignorePackages ignore_flags pkgs0
pkgs0' = filter (not . (`elemFM` (plusFM shadowed ignored)) . installedPackageId) pkgs0
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