Plan build when test components are added #1399

+ changes the ensureConfig logic to ignore the list of components, as it
does not affect the config of the package.

+ avoid reconfigures when the new deps are a subset of the old deps

src/Stack/Build/ConstructPlan.hs

@@ -537,8 +537,8 @@ checkDirtiness ps installed package present wanted = do
 
 describeConfigDiff :: Config -> ConfigCache -> ConfigCache -> Maybe Text
 describeConfigDiff config old new
-    | configCacheDeps old /= configCacheDeps new = Just "dependencies changed"
-    | not $ Set.null $ Set.filter isLibExe newComponents =
+    | not (configCacheDeps new `Set.isSubsetOf` configCacheDeps old) = Just "dependencies changed"
+    | not $ Set.null newComponents =
         Just $ "components added: " `T.append` T.intercalate ", "
             (map (decodeUtf8With lenientDecode) (Set.toList newComponents))
     | not (configCacheHaddock old) && configCacheHaddock new = Just "rebuilding with haddocks"
@@ -550,11 +550,6 @@ describeConfigDiff config old new
         ]
     | otherwise = Nothing
   where
-    isLibExe t = not $ any (`S8.isPrefixOf` t)
-        [ "test:"
-        , "bench:"
-        ]
-
     -- options set by stack
     isStackOpt t = any (`T.isPrefixOf` t)
         [ "--dependency="

src/Stack/Build/Execute.hs

@@ -627,13 +627,19 @@ ensureConfig newConfigCache pkgDir ExecuteEnv {..} announce cabal cabalfp = do
         if boptsReconfigure eeBuildOpts
             then return True
             else do
+                -- We can ignore the components portion of the config
+                -- cache, because it's just used to inform 'construct
+                -- plan that we need to plan to build additional
+                -- components. These components don't affect the actual
+                -- package configuration.
+                let ignoreComponents cc = cc { configCacheComponents = Set.empty }
                 -- Determine the old and new configuration in the local directory, to
                 -- determine if we need to reconfigure.
                 mOldConfigCache <- tryGetConfigCache pkgDir
 
                 mOldCabalMod <- tryGetCabalMod pkgDir
 
-                return $ mOldConfigCache /= Just newConfigCache
+                return $ fmap ignoreComponents mOldConfigCache /= Just (ignoreComponents newConfigCache)
                       || mOldCabalMod /= Just newCabalMod
     let ConfigureOpts dirs nodirs = configCacheOpts newConfigCache
     when needConfig $ withMVar eeConfigureLock $ \_ -> do