Make `AbiHash` opaque & `ShortText`-backed (#3921)

This doesn't have any noteworthy performance impact since
there aren't that many `AbiHash` values to keep track of and is
rather for consistency with the other opaque types.

Cabal/Distribution/InstalledPackageInfo.hs

@@ -146,7 +146,7 @@ emptyInstalledPackageInfo
         synopsis          = "",
         description       = "",
         category          = "",
-        abiHash           = AbiHash "",
+        abiHash           = mkAbiHash "",
         exposed           = False,
         exposedModules    = [],
         hiddenModules     = [],

Cabal/Distribution/Package.hs

@@ -35,7 +35,7 @@ module Distribution.Package (
         Module(..),
 
         -- * ABI hash
-        AbiHash(..),
+        AbiHash, unAbiHash, mkAbiHash,
 
         -- * Package source dependencies
         Dependency(..),
@@ -188,6 +188,8 @@ mkComponentId :: String -> ComponentId
 mkComponentId = ComponentId . toShortText
 
 -- | Convert 'ComponentId' to 'String'
+--
+-- @since 2.0
 unComponentId :: ComponentId -> String
 unComponentId (ComponentId s) = fromShortText s
 
@@ -307,10 +309,36 @@ class (HasUnitId pkg) => PackageInstalled pkg where
 -- -----------------------------------------------------------------------------
 -- ABI hash
 
-newtype AbiHash = AbiHash String
+-- | ABI Hashes
+--
+-- Use 'mkAbiHash' and 'unAbiHash' to convert from/to a
+-- 'String'.
+--
+-- This type is opaque since @Cabal-2.0@
+--
+-- @since 2.0
+newtype AbiHash = AbiHash ShortText
     deriving (Eq, Show, Read, Generic)
+
+-- | Construct a 'AbiHash' from a 'String'
+--
+-- 'mkAbiHash' is the inverse to 'unAbiHash'
+--
+-- Note: No validations are performed to ensure that the resulting
+-- 'AbiHash' is valid
+--
+-- @since 2.0
+unAbiHash :: AbiHash -> String
+unAbiHash (AbiHash h) = fromShortText h
+
+-- | Convert 'AbiHash' to 'String'
+--
+-- @since 2.0
+mkAbiHash :: String -> AbiHash
+mkAbiHash = AbiHash . toShortText
+
 instance Binary AbiHash
 
 instance Text AbiHash where
-    disp (AbiHash abi) = Disp.text abi
-    parse = fmap AbiHash (Parse.munch isAlphaNum)
+    disp = Disp.text . unAbiHash
+    parse = fmap mkAbiHash (Parse.munch isAlphaNum)

Cabal/Distribution/Simple/Build.hs

@@ -222,7 +222,7 @@ buildComponent verbosity numJobs pkg_descr lbi suffixes
     pwd <- getCurrentDirectory
     let -- The in place registration uses the "-inplace" suffix, not an ABI hash
         installedPkgInfo = inplaceInstalledPackageInfo pwd distPref pkg_descr
-                                                       (AbiHash "") lib' lbi clbi
+                                                       (mkAbiHash "") lib' lbi clbi
 
     registerPackage verbosity (compiler lbi) (withPrograms lbi) HcPkg.MultiInstance
                     (withPackageDB lbi) installedPkgInfo
@@ -444,7 +444,7 @@ testSuiteLibV09AsLibAndExe pkg_descr
           , testSuites   = []
           , subLibraries = [lib]
           }
-    ipi    = inplaceInstalledPackageInfo pwd distPref pkg (AbiHash "") lib lbi libClbi
+    ipi    = inplaceInstalledPackageInfo pwd distPref pkg (mkAbiHash "") lib lbi libClbi
     testDir = buildDir lbi </> stubName test
           </> stubName test ++ "-tmp"
     testLibDep = thisPackageVersion $ package pkg

Cabal/Distribution/Simple/GHC/IPI642.hs

@@ -70,7 +70,7 @@ toCurrent ipi@InstalledPackageInfo{} =
     Current.sourcePackageId    = pid,
     Current.installedUnitId    = Current.mkLegacyUnitId pid,
     Current.compatPackageKey   = "",
-    Current.abiHash            = Current.AbiHash "", -- bogus but old GHCs don't care.
+    Current.abiHash            = Current.mkAbiHash "", -- bogus but old GHCs don't care.
     Current.license            = convertLicense (license ipi),
     Current.copyright          = copyright ipi,
     Current.maintainer         = maintainer ipi,

Cabal/Distribution/Simple/Register.hs

@@ -237,10 +237,10 @@ generateRegistrationInfo verbosity pkg lib lbi clbi inplace reloc distPref packa
   abi_hash <-
     case compilerFlavor comp of
      GHC | compilerVersion comp >= mkVersion [6,11] -> do
-            fmap AbiHash $ GHC.libAbiHash verbosity pkg lbi' lib clbi
+            fmap mkAbiHash $ GHC.libAbiHash verbosity pkg lbi' lib clbi
      GHCJS -> do
-            fmap AbiHash $ GHCJS.libAbiHash verbosity pkg lbi' lib clbi
-     _ -> return (AbiHash "")
+            fmap mkAbiHash $ GHCJS.libAbiHash verbosity pkg lbi' lib clbi
+     _ -> return (mkAbiHash "")
 
   installedPkgInfo <-
     if inplace

Cabal/changelog

@@ -52,6 +52,9 @@
 	* Backwards incompatible change to 'ComponentId' (#3917):
 	  'ComponentId' is now opaque; conversion to/from 'String' now works
 	  via 'unComponentId' and 'mkComponentId' functions.
+	* Backwards incompatible change to 'AbiHash' (#3921):
+	  'AbiHash' is now opaque; conversion to/from 'String' now works
+	  via 'unAbiHash' and 'mkAbiHash' functions.
 	* Backwards incompatible change to 'Version' (#3905):
 	  Version is now opaque; conversion to/from '[Int]' now works
 	  via 'versionNumbers' and 'mkVersion' functions.