init: check pkg name and .cabal file name match

Since stack does not allow package name to mismatch with the .cabal file name
stack init should also not allow that. This commit disallows the mismatch.

src/Stack/Solver.hs

@@ -494,15 +494,23 @@ cabalPackagesCheck cabalfps noPkgMsg dupErrMsg = do
     (warnings, gpds) <- fmap unzip (mapM readPackageUnresolved cabalfps)
     zipWithM_ (mapM_ . printCabalFileWarning) cabalfps warnings
 
+    -- package name cannot be empty or missing otherwise
+    -- it will result in cabal solver failure.
+    -- stack requires packages name to match the cabal file name
+    -- Just the latter check is enough to cover both the cases
+
     let packages  = zip cabalfps gpds
-        getEmptyNamePkg (fp, gpd)
-            | ((show . gpdPackageName) gpd) == "" = Just fp
+        getNameMismatchPkg (fp, gpd)
+            | (show . gpdPackageName) gpd /= (FP.takeBaseName . toFilePath) fp
+                = Just fp
             | otherwise = Nothing
-        emptyNamePkgs = mapMaybe getEmptyNamePkg packages
+        nameMismatchPkgs = mapMaybe getNameMismatchPkg packages
 
-    when (emptyNamePkgs /= []) $ do
-        rels <- mapM makeRel emptyNamePkgs
-        error $ "Please assign a name to the following package(s):\n"
+    when (nameMismatchPkgs /= []) $ do
+        rels <- mapM makeRel nameMismatchPkgs
+        error $ "Package name as defined in the .cabal file must match the \
+                \.cabal file name.\n\
+                \Please fix the following packages and try again:\n"
                 <> (formatGroup rels)
 
     let dupGroups = filter ((> 1) . length)