Support custom type tags with multiple parameters

+ Fix a bug in parsing custom type text: Instances in tag parameters need to be enclosed in parentheses.
+ Expand generation of the JSON coding functions to support tags with multiple parameters. Expand the decoders to support the automatic migration of applications from previous versions.
+ Automate tests for the new features, also specifically covering the core types `Maybe` and `Result`.
+ Expand the full-stack demo app to illustrate the new functionality.

+ Also, fix a path in the `demo-backend-state.ps1` script.

implement/PersistentProcess/example-elm-apps/demo-backend-state/demo-backend-state.ps1

@@ -1,4 +1,4 @@
-docker build --tag elm-fullstack-test ./../../
+docker build --tag elm-fullstack-test ./../../../
 
 docker stop fullstack-test-container
 

implement/PersistentProcess/example-elm-apps/demo-backend-state/elm-app/src/Backend/Main.elm

@@ -53,7 +53,10 @@ type alias Tuple3 =
 
 type CustomType
     = CustomTagWithoutParameter
-    | CustomTagWithParameter Int
+    | CustomTagWithOneParameter Int
+    | CustomTagWithTwoParameters String Int
+    | CustomTagWithMaybeInstance (Maybe Int)
+    | CustomTagWithResultInstance (Result String Int)
 
 
 type CustomTypeWithTypeParameter a
@@ -104,7 +107,15 @@ interfaceToHost_initState =
     , lastHttpRequests = []
     , tuple2 = ( 123, "second element in tuple A" )
     , tuple3 = ( 456, "second element in tuple B", 789 )
-    , list_custom_type = [ CustomTagWithoutParameter, CustomTagWithParameter 4 ]
+    , list_custom_type =
+        [ CustomTagWithoutParameter
+        , CustomTagWithOneParameter 4
+        , CustomTagWithTwoParameters "test" 11
+        , CustomTagWithMaybeInstance Nothing
+        , CustomTagWithMaybeInstance (Just 123)
+        , CustomTagWithResultInstance (Err "error string")
+        , CustomTagWithResultInstance (Ok 678)
+        ]
     , opaque_custom_type = OpaqueCustomType "content"
     , recursive_type = TagRecurse (TagRecurse (TagRecurse (TagTerminate 4)))
     , bool = True

implement/elm-fullstack/Program.cs

@@ -10,7 +10,7 @@ namespace elm_fullstack
 {
     class Program
     {
-        static string AppVersionId => "2020-03-02";
+        static string AppVersionId => "2020-03-07";
 
         static int Main(string[] args)
         {

implement/elm-fullstack/elm-fullstack.csproj

@@ -5,8 +5,8 @@
     <TargetFramework>netcoreapp3.1</TargetFramework>
     <RootNamespace>elm_fullstack</RootNamespace>
     <AssemblyName>elm-fullstack</AssemblyName>
-    <AssemblyVersion>2020.0220.0.0</AssemblyVersion>
-    <FileVersion>2020.0220.0.0</FileVersion>
+    <AssemblyVersion>2020.0307.0.0</AssemblyVersion>
+    <FileVersion>2020.0307.0.0</FileVersion>
   </PropertyGroup>
 
   <ItemGroup>

implement/test/modeled-in-elm/generate-json-coders/elm.json

@@ -9,7 +9,8 @@
             "elm/browser": "1.0.2",
             "elm/core": "1.0.5",
             "elm/html": "1.0.0",
-            "elm/json": "1.1.3"
+            "elm/json": "1.1.3",
+            "elm-community/result-extra": "2.3.0"
         },
         "indirect": {
             "elm/time": "1.0.0",

implement/test/modeled-in-elm/generate-json-coders/src/Main.elm

@@ -1,21 +1,112 @@
 module Main exposing (main)
 
 import ElmFullstackLoweringInterface.GenerateJsonCoders as GenerateJsonCoders
+import Json.Decode
 import Json.Encode
 import OpaqueCustomType
+import Result.Extra
+import Structures
 
 
 tests : String
 tests =
     [ { testName = "serialize non-exposed tag of custom type"
-      , expected = """{"int":4,"opaqueCustomType":{"TagA":{}}}"""
+      , expected = """{"int":4,"opaqueCustomType":{"TagA":[]},"list_custom_type":[]}"""
       , derived =
             { int = 4
             , opaqueCustomType = OpaqueCustomType.constructTagA
+            , list_custom_type = []
             }
                 |> GenerateJsonCoders.encodeMixedRecord
                 |> Json.Encode.encode 0
       }
+    , { testName = "Custom type tag with one parameter"
+      , expected = """{"int":4,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithOneParameter":[13]}]}"""
+      , derived =
+            { int = 4
+            , opaqueCustomType = OpaqueCustomType.constructTagA
+            , list_custom_type = [ Structures.CustomTagWithOneParameter 13 ]
+            }
+                |> GenerateJsonCoders.encodeMixedRecord
+                |> Json.Encode.encode 0
+      }
+    , { testName = "Custom type tag with two parameters"
+      , expected = """{"int":4,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithTwoParameters":["first arg",17]}]}"""
+      , derived =
+            { int = 4
+            , opaqueCustomType = OpaqueCustomType.constructTagA
+            , list_custom_type = [ Structures.CustomTagWithTwoParameters "first arg" 17 ]
+            }
+                |> GenerateJsonCoders.encodeMixedRecord
+                |> Json.Encode.encode 0
+      }
+    , { testName = "Custom type tag with two parameters - roundtrip"
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithTwoParameters":["first arg",19]}]}"""
+      , derived =
+            """{"int"   : 7 , "opaqueCustomType" : { "TagA" : []}, "list_custom_type":[{"CustomTagWithTwoParameters":["first arg",19]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Maybe - Just roundtrip"
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Just":[37]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Just":[37]}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Maybe - Nothing roundtrip"
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Nothing":[]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Nothing":[]}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Result - Ok roundtrip"
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Ok":[37]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Ok":[37]}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Result - Err roundtrip"
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Err":["error string"]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Err":["error string"]}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Maybe - support easy migration from older format."
+
+      -- 2020-03-07 Support easy migration of apps: Support decode from older JSON format for now. This case can be removed when the apps have been migrated.
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Just":[37]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithMaybeInstance":[{"Just":37}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
+    , { testName = "Result - support easy migration from older format."
+
+      -- 2020-03-07 Support easy migration of apps: Support decode from older JSON format for now. This case can be removed when the apps have been migrated.
+      , expected = """{"int":7,"opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Ok":[37]}]}]}"""
+      , derived =
+            """{"int" :     7, "opaqueCustomType":{"TagA":[]},"list_custom_type":[{"CustomTagWithResultInstance":[{"Ok":37}]}]}"""
+                |> Json.Decode.decodeString GenerateJsonCoders.decodeMixedRecord
+                |> Result.map (GenerateJsonCoders.encodeMixedRecord >> Json.Encode.encode 0)
+                |> Result.mapError Json.Decode.errorToString
+                |> Result.Extra.merge
+      }
     ]
         |> GenerateJsonCoders.testsValueToInterface
         |> Json.Encode.encode 0

implement/test/modeled-in-elm/generate-json-coders/src/Structures.elm

@@ -6,4 +6,13 @@ import OpaqueCustomType exposing (OpaqueCustomType)
 type alias MixedRecord =
     { int : Int
     , opaqueCustomType : OpaqueCustomType
+    , list_custom_type : List CustomType
     }
+
+
+type CustomType
+    = CustomTagWithoutParameter
+    | CustomTagWithOneParameter Int
+    | CustomTagWithTwoParameters String Int
+    | CustomTagWithMaybeInstance (Maybe Int)
+    | CustomTagWithResultInstance (Result String Int)