Suggest stack init when using implicit global

Author: snoyberg

src/Stack/Build/Source.hs

@@ -87,6 +87,7 @@ loadSourceMap bopts = do
     workingDir <- getWorkingDir
     (cliExtraDeps, targets) <-
         parseTargets
+            (bcImplicitGlobal bconfig)
             (boptsTests bopts)
             (boptsBenchmarks bopts)
             (mpiVersion <$> mbpPackages mbp0)

src/Stack/Build/Target.hs

@@ -285,15 +285,16 @@ simplifyTargets includeTests includeBenches =
     getLocalComp _ = Left ()
 
 parseTargets :: (MonadThrow m, MonadIO m)
-             => Bool -- ^ include tests
+             => Bool -- ^ using implicit global?
+             -> Bool -- ^ include tests
              -> Bool -- ^ include benchmarks
              -> Map PackageName Version -- ^ snapshot
              -> Map PackageName Version -- ^ extra deps
              -> Map PackageName LocalPackageView
              -> Path Abs Dir -- ^ current directory
              -> [Text] -- ^ command line targets
              -> m (Map PackageName Version, Map PackageName SimpleTarget)
-parseTargets includeTests includeBenches snap extras locals currDir textTargets' = do
+parseTargets implicitGlobal includeTests includeBenches snap extras locals currDir textTargets' = do
     let textTargets =
             if null textTargets'
                 then map (T.pack . packageNameString) $ Map.keys $ Map.filter (not . lpvExtraDep) locals
@@ -310,8 +311,9 @@ parseTargets includeTests includeBenches snap extras locals currDir textTargets'
 
     if null errs
         then if Map.null targets
-                 -- TODO perhaps check if we're using the implicit global and,
-                 -- if so, recommend running stack init/new?
-                 then throwM $ TargetParseException ["The specified targets matched no packages"]
+                 then throwM $ TargetParseException
+                        $ if implicitGlobal
+                            then ["The specified targets matched no packages.\nPerhaps you need to run 'stack init'?"]
+                            else ["The specified targets matched no packages"]
                  else return (Map.unions newExtras, targets)
         else throwM $ TargetParseException errs

src/Stack/Config.hs

@@ -296,6 +296,7 @@ loadBuildConfig mproject config stackRoot mresolver = do
         , bcExtraDeps = projectExtraDeps project
         , bcStackYaml = stackYamlFP
         , bcFlags = projectFlags project
+        , bcImplicitGlobal = isNothing mproject
         }
 
 -- | Resolve a PackageEntry into a list of paths, downloading and cloning as

src/Stack/Types/Config.hs

@@ -240,6 +240,9 @@ data BuildConfig = BuildConfig
       -- different from bcRoot </> "stack.yaml"
     , bcFlags      :: !(Map PackageName (Map FlagName Bool))
       -- ^ Per-package flag overrides
+    , bcImplicitGlobal :: !Bool
+      -- ^ Are we loading from the implicit global stack.yaml? This is useful
+      -- for providing better error messages.
     }
 
 -- | Directory containing the project's stack.yaml file