Package keys (for linking/type equality) separated from package IDs.

This patch set makes us no longer assume that a package key is a human
readable string, leaving Cabal free to "do whatever it wants" to allocate
keys; we'll look up the PackageId in the database to display to the user.
This also means we have a new level of qualifier decisions to make at the
package level, and rewriting some Safe Haskell error reporting code to DTRT.

Additionally, we adjust the build system to use a new ghc-cabal output
Make variable PACKAGE_KEY to determine library names and other things,
rather than concatenating PACKAGE/VERSION as before.

Adds a new `-this-package-key` flag to subsume the old, erroneously named
`-package-name` flag, and `-package-key` to select packages by package key.

RFC: The md5 hashes are pretty tough on the eye, as far as the file
system is concerned :(

ToDo: safePkg01 test had its output updated, but the fix is not really right:
the rest of the dependencies are truncated due to the fact the we're only
grepping a single line, but ghc-pkg is wrapping its output.

ToDo: In a later commit, update all submodules to stop using -package-name
and use -this-package-key.  For now, we don't do it to avoid submodule
explosion.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, simonmar, hvr, austin

Subscribers: simonmar, relrod, carter

Differential Revision: https://phabricator.haskell.org/D80

1 files changed, 10 insertions, 9 deletions

diff --git a/compiler/main/PackageConfig.hs b/compiler/main/PackageConfig.hs
index 520b533380..864980be9d 100644
--- a/compiler/main/PackageConfig.hs
+++ b/compiler/main/PackageConfig.hs
@@ -26,7 +26,8 @@ module PackageConfig (
 
 import Distribution.InstalledPackageInfo
 import Distribution.ModuleName
-import Distribution.Package
+import Distribution.Package hiding (PackageKey, mkPackageKey)
+import qualified Distribution.Package as Cabal
 import Distribution.Text
 import Distribution.Version
 
@@ -43,23 +44,23 @@ defaultPackageConfig :: PackageConfig
 defaultPackageConfig = emptyInstalledPackageInfo
 
 -- -----------------------------------------------------------------------------
--- PackageKey (package names with versions)
+-- PackageKey (package names, versions and dep hash)
 
 -- $package_naming
 -- #package_naming#
--- Mostly the compiler deals in terms of 'PackageKey's, which have the
--- form @<pkg>-<version>@. You're expected to pass in the version for
--- the @-package-name@ flag. However, for wired-in packages like @base@
--- & @rts@, we don't necessarily know what the version is, so these are
--- handled specially; see #wired_in_packages#.
+-- Mostly the compiler deals in terms of 'PackageKey's, which are md5 hashes
+-- of a package ID, keys of its dependencies, and Cabal flags. You're expected
+-- to pass in the package key in the @-this-package-key@ flag. However, for
+-- wired-in packages like @base@ & @rts@, we don't necessarily know what the
+-- version is, so these are handled specially; see #wired_in_packages#.
 
 -- | Turn a Cabal 'PackageIdentifier' into a GHC 'PackageKey'
-mkPackageKey :: PackageIdentifier -> PackageKey
+mkPackageKey :: Cabal.PackageKey -> PackageKey
 mkPackageKey = stringToPackageKey . display
 
 -- | Get the GHC 'PackageKey' right out of a Cabalish 'PackageConfig'
 packageConfigId :: PackageConfig -> PackageKey
-packageConfigId = mkPackageKey . sourcePackageId
+packageConfigId = mkPackageKey . packageKey
 
 -- | Turn a 'PackageConfig', which contains GHC 'Module.ModuleName's into a Cabal specific
 -- 'InstalledPackageInfo' which contains Cabal 'Distribution.ModuleName.ModuleName's