language: fix: compute correct source root when building dar (#2500)

* language: fix: compute correct source root when building dar

Previously we just took the base directory of the main file, which is
wrong when the main is deeper down in the module structure.

* hlinting

* reuse moduleImportPaths

compiler/damlc/daml-compiler/src/DA/Daml/Compiler/Dar.hs

@@ -12,6 +12,9 @@ import qualified Codec.Archive.Zip as Zip
 import Control.Monad.Extra
 import Control.Monad.IO.Class
 import Control.Monad.Trans.Maybe
+import qualified DA.Daml.LF.Ast as LF
+import DA.Daml.LF.Proto3.Archive (encodeArchiveAndHash)
+import DA.Daml.Options.Types
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Lazy as BSL
 import qualified Data.ByteString.Lazy.Char8 as BSC
@@ -20,19 +23,15 @@ import qualified Data.Map.Strict as Map
 import Data.Maybe
 import qualified Data.Set as S
 import qualified Data.Text as T
-import System.FilePath
-
-import Module (unitIdString)
-
-import qualified DA.Daml.LF.Ast as LF
-import DA.Daml.LF.Proto3.Archive (encodeArchiveAndHash)
-import DA.Daml.Options.Types
 import Development.IDE.Core.API
 import Development.IDE.Core.RuleTypes.Daml
 import Development.IDE.Core.Rules.Daml
+import Development.IDE.GHC.Util
 import Development.IDE.Types.Location
 import qualified Development.IDE.Types.Logger as IdeLogger
+import Module
 import SdkVersion
+import System.FilePath
 
 ------------------------------------------------------------------------------
 {- | Builds a dar file.
@@ -88,10 +87,15 @@ buildDar service pkgConf@PackageConfigFields {..} ifDir dalfInput = do
         then liftIO $
              Just <$> do
                  bytes <- BSL.readFile pMain
-                 createArchive pkgConf "" bytes [] [] [] []
+                 createArchive pkgConf "" bytes [] (toNormalizedFilePath ".") [] [] []
         else runAction service $
              runMaybeT $ do
                  WhnfPackage pkg <- useE GeneratePackage file
+                 parsedMain <- useE GetParsedModule file
+                 let srcRoot =
+                         toNormalizedFilePath $
+                         fromMaybe (error "Cannot determine source root") $
+                         moduleImportPaths parsedMain
                  let pkgModuleNames = map T.unpack $ LF.packageModuleNames pkg
                  let missingExposed =
                          S.fromList (fromMaybe [] pExposedModules) S.\\
@@ -120,6 +124,7 @@ buildDar service pkgConf@PackageConfigFields {..} ifDir dalfInput = do
                          (T.unpack pkgId)
                          dalf
                          dalfDependencies
+                         srcRoot
                          (file : fileDependencies)
                          dataFiles
                          ifaces
@@ -167,11 +172,12 @@ createArchive ::
     -> String
     -> BSL.ByteString -- ^ DALF
     -> [(T.Text, BS.ByteString)] -- ^ DALF dependencies
+    -> NormalizedFilePath -- ^ Source root directory
     -> [NormalizedFilePath] -- ^ Module dependencies
     -> [(String, BS.ByteString)] -- ^ Data files
     -> [NormalizedFilePath] -- ^ Interface files
     -> IO BSL.ByteString
-createArchive PackageConfigFields {..} pkgId dalf dalfDependencies fileDependencies dataFiles ifaces
+createArchive PackageConfigFields {..} pkgId dalf dalfDependencies srcRoot fileDependencies dataFiles ifaces
  = do
     -- Reads all module source files, and pairs paths (with changed prefix)
     -- with contents as BS. The path must be within the module root path, and
@@ -181,14 +187,14 @@ createArchive PackageConfigFields {..} pkgId dalf dalfDependencies fileDependenc
             contents <- BSL.readFile $ fromNormalizedFilePath mPath
             return
                 ( pkgName </>
-                  fromNormalizedFilePath (makeRelative' modRoot mPath)
+                  fromNormalizedFilePath (makeRelative' srcRoot mPath)
                 , contents)
     ifaceFaceFiles <-
         forM ifaces $ \mPath -> do
             contents <- BSL.readFile $ fromNormalizedFilePath mPath
             let ifaceRoot =
                     toNormalizedFilePath
-                        (ifaceDir </> fromNormalizedFilePath modRoot)
+                        (ifaceDir </> fromNormalizedFilePath srcRoot)
             return
                 ( pkgName </>
                   fromNormalizedFilePath (makeRelative' ifaceRoot mPath)
@@ -214,7 +220,6 @@ createArchive PackageConfigFields {..} pkgId dalf dalfDependencies fileDependenc
     pure $ Zip.fromArchive zipArchive
   where
     pkgName = fullPkgName pName pVersion pkgId
-    modRoot = toNormalizedFilePath $ takeDirectory pMain
     manifestHeader :: FilePath -> [String] -> BSL.ByteString
     manifestHeader location dalfs =
         BSC.pack $