Types constraint shift for Bridge.elm should refresh on file changes else user gets stale type inference errors when applying the technique

Author: supermario

extra/Lamdera/Constrain.hs

@@ -21,43 +21,36 @@ import Lamdera.Project (lamderaCore)
 
 
 constrain pkg modu name annotation@(Can.Forall freevars t) region expected =
-  if pkg == lamderaCore && modu == "Lamdera" && name == "sendToBackend" then
-    do
-      sourcePkg <- determineTypesLocation "ToBackend"
-      let
-        fn (Can.TVar "toBackend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToBackend" []
-        fn x = x
-      pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
-
-  else if pkg == lamderaCore && modu == "Lamdera" && name == "sendToFrontend" then
-    do
-      sourcePkg <- determineTypesLocation "ToFrontend"
-      let
-        fn (Can.TVar "toFrontend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToFrontend" []
-        fn x = x
-      pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
-
-  else if pkg == lamderaCore && modu == "Lamdera" && name == "broadcast" then
-    do
-      sourcePkg <- determineTypesLocation "ToFrontend"
-      let
-        fn (Can.TVar "toFrontend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToFrontend" []
-        fn x = x
-      pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
+  if pkg == lamderaCore && modu == "Lamdera" then
+
+    case name of
+      "sendToBackend" -> do
+        sourcePkg <- determineTypesLocation "ToBackend"
+        let
+          fn (Can.TVar "toBackend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToBackend" []
+          fn x = x
+        pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
+
+      "sendToFrontend" -> do
+        sourcePkg <- determineTypesLocation "ToFrontend"
+        let
+          fn (Can.TVar "toFrontend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToFrontend" []
+          fn x = x
+        pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
+
+      "broadcast" -> do
+        sourcePkg <- determineTypesLocation "ToFrontend"
+        let
+          fn (Can.TVar "toFrontend") = Can.TType (ModuleName.Canonical Pkg.dummyName sourcePkg) "ToFrontend" []
+          fn x = x
+        pure $ CForeign region name (Can.Forall freevars (mapTvars fn t)) expected
+
+      _ ->
+        pure $ CForeign region name annotation expected
 
   else
     pure $ CForeign region name annotation expected
 
-  -- @LEGACY, left here in case we run into issues, but likely no longer needed.
-  -- Since we don't have type annotations on codecs, we have exposed top-level
-  -- things without type annotations, which means that we see bugs in the type
-  -- inference engine that shouldn't be there. This is a hotfix for such a bug,
-  -- where the forall. part of the type doesn't hold all the tvars used in the
-  -- type, so we inject any missning tvars and hope it works out.
-  -- @LAMDERA todo legacy from Haskell transpilation, re-evalutate and remove
-  -- else
-  --   pure $ CForeign region name (Can.Forall (freevars <> getFreevars t) t) expected -- NOTE: prefer freevars over getFreevars if there's a conflict
-
 
 determineTypesLocation :: Text -> IO N.Name
 determineTypesLocation tipe = do
@@ -94,6 +87,8 @@ determineTypesLocation tipe = do
 typeLocations :: IORef (Map.Map Text N.Name)
 typeLocations = unsafePerformIO $ newIORef Map.empty
 
+resetTypeLocations :: IO ()
+resetTypeLocations = atomicModifyIORef typeLocations (\m -> (Map.empty, ()))
 
 rememberTypeLocation :: Text -> N.Name -> IO ()
 rememberTypeLocation str d = atomicModifyIORef typeLocations (\m -> (Map.insert str d m, ()))

terminal/src/Develop.hs

@@ -42,6 +42,7 @@ import qualified Stuff
 
 import Lamdera
 import qualified Lamdera.CLI.Live as Live
+import qualified Lamdera.Constrain
 import qualified Lamdera.ReverseProxy
 import qualified Lamdera.TypeHash
 import qualified Lamdera.PostCompile
@@ -92,6 +93,12 @@ runWithRoot root (Flags maybePort) =
           Sentry.asyncUpdateJsOutput sentryCache $ do
             debug_ $ "🛫  recompile triggered by: " ++ show events
             harness <- Live.prepareLocalDev root
+            let
+              typesRootChanged = events & filter (\event ->
+                     stringContains "src/Types.elm" event
+                  || stringContains "src/Bridge.elm" event
+                ) & length & (\v -> v > 0)
+            onlyWhen typesRootChanged Lamdera.Constrain.resetTypeLocations
             compileToBuilder harness
           -- Simultaneously tell all clients to refresh. All those HTTP
           -- requests will open but block on the cache mVar, and then release