Support wildcard build-tool-depends entries in Cabal

They look like

 pkg:* <optional version bound>

and denote a dependency on every executable in the package. In the case of
internal package dependencies, it is easy to expand the wildcard for
internal dependencies, but not possible in Cabal alone for external ones,
as the exact set of exe deps depends on the version resolved in
cabal-install's build plan.

Author: Ericson2314

Cabal/Distribution/PackageDescription/Check.hs

@@ -635,7 +635,7 @@ checkFields pkg =
 
     depMissingInternalExecutable =
       [ dep
-      | dep@(ExeDependency _ eName _) <- internalExeDeps
+      | dep@(ExeDependency _ (Just eName) _) <- internalExeDeps
       , not $ eName `elem` internalExecutables
       ]
 

Cabal/Distribution/Parsec/Class.hs

@@ -141,7 +141,7 @@ instance Parsec ExeDependency where
     parsec = do
         name <- lexemeParsec
         _    <- P.char ':'
-        exe  <- lexemeParsec
+        exe  <- (Just <$> lexemeParsec) <|> (P.char '*' >> pure Nothing)
         ver  <- parsec <|> pure anyVersion
         return (ExeDependency name exe ver)
 

Cabal/Distribution/Simple/BuildToolDepends.hs

@@ -34,7 +34,7 @@ desugarBuildTool :: PackageDescription
                  -> Maybe ExeDependency
 desugarBuildTool pkg led =
   if foundLocal
-  then Just $ ExeDependency (packageName pkg) toolName reqVer
+  then Just $ ExeDependency (packageName pkg) (Just toolName) reqVer
   else Map.lookup name whiteMap
   where
     LegacyExeDependency name reqVer = led
@@ -44,7 +44,7 @@ desugarBuildTool pkg led =
                 , "cpphs", "greencard", "hspec-discover"
                 ]
     whiteMap  = Map.fromList $ flip map whitelist $ \n ->
-      (n, ExeDependency (mkPackageName n) (mkUnqualComponentName n) reqVer)
+      (n, ExeDependency (mkPackageName n) (Just $ mkUnqualComponentName n) reqVer)
 
 -- | Get everything from "build-tool-depends", along with entries from
 -- "build-tools" that we know how to desugar.
@@ -84,13 +84,20 @@ isInternal pkg (ExeDependency n _ _) = n == packageName pkg
 
 -- | Get internal "build-tool-depends", along with internal "build-tools"
 --
--- This is a tiny function, but used in a number of places. The same
--- restrictions that apply to `isInternal` also apply to this function.
+-- Besides filtering to just internal deps, this also desugars wildcard deps
+-- since we know the same version/configuration of the package will be used to
+-- install them, and thus we know the precise set of executables that wildcard
+-- expands to.
+--
+-- The same restrictions that apply to `isInternal` also apply to this function.
 getAllInternalToolDependencies :: PackageDescription
                                -> BuildInfo
                                -> [UnqualComponentName]
 getAllInternalToolDependencies pkg bi =
   [ toolname
-  | dep@(ExeDependency _ toolname _) <- getAllToolDependencies pkg bi
+  | dep@(ExeDependency _ optToolname _) <- getAllToolDependencies pkg bi
   , isInternal pkg dep
+  , toolname <- case optToolname of
+      Just tn -> pure tn
+      Nothing -> exeName <$> executables pkg
   ]

Cabal/Distribution/Simple/Configure.hs

@@ -571,6 +571,9 @@ configure (pkg_descr0', pbi) cfg = do
          ++ intercalate "," unsupportedFLibs
 
     -- Configure certain external build tools, see below for which ones.
+    --
+    -- TODO: HACK we're currently ignoring wildcard deps as we don't know
+    -- precisely which executables the resolved package will contain.
     let requiredBuildTools = do
           bi <- enabledBuildInfos pkg_descr enabled
           -- First, we collect any tool dep that we know is external. This is,
@@ -581,7 +584,7 @@ configure (pkg_descr0', pbi) cfg = do
           -- 2. `build-tool-depends` that aren't from the current package.
           let externBuildToolDeps =
                 [ LegacyExeDependency (unUnqualComponentName eName) versionRange
-                | buildTool@(ExeDependency _ eName versionRange)
+                | buildTool@(ExeDependency _ (Just eName) versionRange)
                   <- getAllToolDependencies pkg_descr bi
                 , not $ isInternal pkg_descr buildTool ]
           -- Second, we collect any build-tools entry we don't know how to

Cabal/Distribution/Types/ExeDependency.hs

@@ -23,7 +23,9 @@ import Text.PrettyPrint ((<+>), text)
 --
 data ExeDependency = ExeDependency
                      PackageName
-                     UnqualComponentName -- name of executable component of package
+                     -- Name of specific executable component of package, or
+                     -- nothing for a wilcard dependency on them all
+                     (Maybe UnqualComponentName)
                      VersionRange
                      deriving (Generic, Read, Show, Eq, Typeable, Data)
 
@@ -32,15 +34,18 @@ instance NFData ExeDependency where rnf = genericRnf
 
 instance Text ExeDependency where
   disp (ExeDependency name exe ver) =
-    (disp name <<>> text ":" <<>> disp exe) <+> disp ver
+    (disp name <<>> text ":" <<>> exe') <+> disp ver
+    where exe' = case exe of
+            Just e  -> disp e
+            Nothing -> text "*"
 
   parse = do name <- parse
              _ <- Parse.char ':'
-             exe <- parse
+             exe <- (Just <$> parse) <++ (Parse.char '*' >> pure Nothing)
              Parse.skipSpaces
              ver <- parse <++ return anyVersion
              Parse.skipSpaces
              return (ExeDependency name exe ver)
 
-qualifiedExeName :: ExeDependency -> ComponentName
-qualifiedExeName (ExeDependency _ ucn _) = CExeName ucn
+qualifiedExeName :: ExeDependency -> Maybe ComponentName
+qualifiedExeName (ExeDependency _ ucn _) = CExeName <$> ucn