Fix issues with finding Cabal files and disambiguating targets

README.md

@@ -39,8 +39,8 @@ Command-line arguments:
 
 * `ARGS`
 
-  Optional package component (wildcards such as `exe`,
-  `test` or `bench` are supported) to update, followed
+  Optional [target](https://cabal.readthedocs.io/en/latest/cabal-commands.html#target-forms)
+  (wildcards such as `exe`, `test` or `bench` are supported) to update, followed
   by a non-empty list of package(s) to add to
   `build-depends` section. Version bounds can be
   provided as well, use quotes to escape comparisons

app/Main.hs

@@ -18,6 +18,7 @@ import Data.Either (partitionEithers)
 import Data.List qualified as L
 import Data.List.NonEmpty (NonEmpty (..))
 import Data.Maybe (catMaybes)
+import Distribution.CabalSpecVersion (CabalSpecVersion)
 import Distribution.Client.Add
 import Distribution.Fields (Field)
 import Distribution.PackageDescription (
@@ -46,6 +47,7 @@ import Options.Applicative.NonEmpty (some1)
 import System.Directory (doesFileExist, listDirectory)
 import System.Environment (getArgs, withArgs)
 import System.Exit (die)
+import System.FilePath (takeDirectory, (</>))
 
 data RawConfig = RawConfig
   { rcnfMProjectFile :: !(Maybe FilePath)
@@ -100,7 +102,7 @@ extractCabalFilesFromProject projectFn = do
   resolved <- resolveProject projectFn parsed
   case resolved of
     Left exc -> throwIO exc
-    Right prj -> pure $ prjPackages prj
+    Right prj -> pure $ map (takeDirectory projectFn </>) $ prjPackages prj
 
 resolveCabalFiles :: Maybe FilePath -> IO [FilePath]
 resolveCabalFiles = \case
@@ -126,33 +128,59 @@ stripAdd :: [String] -> [String]
 stripAdd ("add" : xs) = xs
 stripAdd xs = xs
 
+type Input =
+  ( FilePath
+  , ByteString
+  , [Field Position]
+  , GenericPackageDescription
+  , Either
+      CommonStanza
+      ComponentName
+  , NonEmpty ByteString
+  )
+
 mkInputs
-  :: FilePath
+  :: Bool
+  -> FilePath
   -> ByteString
   -> NonEmpty String
-  -> Either
-      String
-      ( FilePath
-      , ByteString
-      , [Field Position]
-      , GenericPackageDescription
-      , Either
-          CommonStanza
-          ComponentName
-      , NonEmpty ByteString
-      )
-mkInputs cabalFile origContents args = do
+  -> Either String Input
+mkInputs isCmpRequired cabalFile origContents args = do
   (fields, packDescr) <- parseCabalFile cabalFile origContents
-  let specVer = specVersion $ packageDescription packDescr
+  let specVer :: CabalSpecVersion
+      specVer = specVersion $ packageDescription packDescr
+      mkCmp :: Maybe String -> Either String (Either CommonStanza ComponentName)
       mkCmp = resolveComponent cabalFile (fields, packDescr)
+      mkDeps :: NonEmpty String -> Either String (NonEmpty ByteString)
       mkDeps = traverse (validateDependency specVer)
   (cmp, deps) <- case args of
     x :| (y : ys)
       | Right c <- mkCmp (Just x) ->
           (c,) <$> mkDeps (y :| ys)
-    _ -> (,) <$> mkCmp Nothing <*> mkDeps args
+    _ ->
+      if isCmpRequired
+        then Left "Component is required"
+        else (,) <$> mkCmp Nothing <*> mkDeps args
   pure (cabalFile, origContents, fields, packDescr, cmp, deps)
 
+disambiguateInputs
+  :: Maybe FilePath
+  -> [FilePath]
+  -> [Either a Input]
+  -> Either String Input
+disambiguateInputs mProjectFile cabalFiles inputs = case partitionEithers inputs of
+  ([], []) -> Left $ case mProjectFile of
+    Nothing -> "No Cabal files or projects are found in the current folder, please specify --project-file."
+    Just projFn -> "No Cabal files are found in " ++ projFn
+  (_errs, []) ->
+    Left $
+      "No matching targets found amongst: "
+        ++ L.intercalate ", " cabalFiles
+  (_, [inp]) -> pure inp
+  (_, _inps) ->
+    Left $
+      "Target component is ambiguous, please specify it as package:type:component. See https://cabal.readthedocs.io/en/latest/cabal-commands.html#target-forms for reference"
+
 main :: IO ()
 main = do
   rawArgs <- getArgs
@@ -167,21 +195,11 @@ main = do
   cabalFilesAndContent <-
     catMaybes
       <$> traverse (\fn -> fmap (fn,) <$> readCabalFile fn) cabalFiles
-  let inputs = map (\(fn, cnt) -> mkInputs fn cnt rcnfArgs) cabalFilesAndContent
+  let getInput isCmpRequired =
+        disambiguateInputs rcnfMProjectFile (fmap fst cabalFilesAndContent) $
+          map (\(fn, cnt) -> mkInputs isCmpRequired fn cnt rcnfArgs) cabalFilesAndContent
 
-  input <- case partitionEithers inputs of
-    ([], []) -> die $ case rcnfMProjectFile of
-      Nothing -> "No Cabal files or projects are found in the current folder, specify --project-file."
-      Just projFn -> "No Cabal files are found in " ++ projFn
-    (_errs, []) ->
-      die $
-        "No valid targets found amongst: "
-          ++ L.intercalate ", " (fmap fst cabalFilesAndContent)
-    (_, [inp]) -> pure inp
-    (_, inps) ->
-      die $
-        "Cabal file is ambiguous. Possible targets are: "
-          ++ L.intercalate ", " (map (\(a, _, _, _, _, _) -> a) inps)
+  input <- either (const $ either die pure $ getInput True) pure (getInput False)
 
   let (cabalFile, cnfOrigContents, cnfFields, origPackDescr, cnfComponent, cnfDependencies) = input
 

cabal-add.cabal

@@ -61,6 +61,7 @@ executable cabal-add
         cabal-add,
         cabal-install-parsers >=0.4.1 && <0.7,
         directory <1.4,
+        filepath <1.6,
         optparse-applicative >=0.16 && <0.19,
         process <1.7
 

src/Distribution/Client/Add.hs

@@ -20,6 +20,8 @@ module Distribution.Client.Add (
   validateChanges,
 ) where
 
+import Control.Applicative ((<|>))
+import Control.Monad (guard)
 import Control.Monad.Error.Class (MonadError, throwError)
 import Data.ByteString (ByteString)
 import Data.ByteString.Char8 qualified as B
@@ -46,6 +48,8 @@ import Distribution.PackageDescription (
   PackageDescription (..),
   componentNameStanza,
   componentNameString,
+  pkgName,
+  unPackageName,
   unUnqualComponentName,
  )
 import Distribution.PackageDescription.Configuration (flattenPackageDescription)
@@ -54,8 +58,16 @@ import Distribution.PackageDescription.Parsec (
   parseGenericPackageDescriptionMaybe,
   runParseResult,
  )
-import Distribution.Parsec (Position (..), eitherParsec, showPError)
-import Distribution.Simple.BuildTarget (BuildTarget (BuildTargetComponent), readUserBuildTargets, resolveBuildTargets)
+import Distribution.Parsec (
+  Position (..),
+  eitherParsec,
+  showPError,
+ )
+import Distribution.Simple.BuildTarget (
+  BuildTarget (BuildTargetComponent),
+  readUserBuildTargets,
+  resolveBuildTargets,
+ )
 
 -- | Just a newtype wrapper, since @Cabal-syntax@ does not provide any.
 newtype CommonStanza = CommonStanza {unCommonStanza :: ByteString}
@@ -219,13 +231,25 @@ parseCabalFile fileName contents = do
   pure (fields, packDescr)
 
 readBuildTarget :: PackageDescription -> String -> Maybe ComponentName
-readBuildTarget pkg targetStr = do
+readBuildTarget pkg targetStr =
+  readBuildTarget' pkg targetStr <|> readBuildTarget'' pkg targetStr
+
+readBuildTarget' :: PackageDescription -> String -> Maybe ComponentName
+readBuildTarget' pkg targetStr = do
   let (_, utargets) = readUserBuildTargets [targetStr]
   [utarget] <- pure utargets
   let (_, btargets) = resolveBuildTargets pkg [(utarget, False)]
   [BuildTargetComponent btarget] <- pure btargets
   pure btarget
 
+-- | Surprisingly, 'resolveBuildTargets' does not support package component.
+-- Let's work around this limitation manually for now.
+readBuildTarget'' :: PackageDescription -> String -> Maybe ComponentName
+readBuildTarget'' pkg targetStr = do
+  (pref, ':' : suff) <- pure $ span (/= ':') targetStr
+  guard $ unPackageName (pkgName (package pkg)) == pref
+  readBuildTarget' pkg suff
+
 -- | Resolve a raw component name.
 resolveComponent
   :: MonadError String m