Warn on spaces in module names

Author: sol

src/Hpack/Module.hs

@@ -33,7 +33,11 @@ instance IsString Module where
   fromString = Module
 
 instance FromValue Module where
-  fromValue = fmap Module . fromValue
+  fromValue v = do
+    r <- fromValue v
+    case words r of
+      [name] -> return (Module name)
+      _ -> warn ("invalid module name " <> show r) >> return (Module r)
 
 toModule :: Path -> Module
 toModule path = case reverse $ Path.components path of

test/EndToEndSpec.hs

@@ -70,6 +70,17 @@ spec = around_ (inTempDirectoryNamed "foo") $ do
           "package.yaml: Duplicate field $.name"
         ]
 
+    context "when a module name contains spaces" $ do
+      it "warns" $ do
+        [i|
+        name: foo
+        library:
+          other-modules:
+            Foo
+            Bar
+            Baz
+        |] `shouldWarn` ["package.yaml: invalid module name \"Foo Bar Baz\" in $.library.other-modules"]
+
     describe "handling of Paths_ module" $ do
       it "adds Paths_ to other-modules" $ do
         [i|