Add a SetField helper.

examples/smoothies/app/Effect.elm

@@ -15,6 +15,7 @@ type Effect msg
     | Cmd (Cmd msg)
     | Batch (List (Effect msg))
     | GetStargazers (Result Http.Error Int -> msg)
+    | SetField { formId : String, name : String, value : String }
     | FetchRouteData
         { data : Maybe FormDecoder.FormData
         , toMsg : Result Http.Error Url -> msg
@@ -74,6 +75,9 @@ map fn effect =
                 , toMsg = fetchInfo.toMsg >> fn
                 }
 
+        SetField info ->
+            SetField info
+
         SubmitFetcher fetcher ->
             fetcher
                 |> Pages.Fetcher.map fn
@@ -96,6 +100,7 @@ perform :
         -> Cmd msg
     , fromPageMsg : pageMsg -> msg
     , key : Browser.Navigation.Key
+    , setField : { formId : String, name : String, value : String } -> Cmd msg
     }
     -> Effect pageMsg
     -> Cmd msg
@@ -107,6 +112,9 @@ perform ({ fromPageMsg, key } as helpers) effect =
         Cmd cmd ->
             Cmd.map fromPageMsg cmd
 
+        SetField info ->
+            helpers.setField info
+
         Batch list ->
             Cmd.batch (List.map (perform helpers) list)
 

src/Pages/Form.elm

@@ -89,6 +89,33 @@ update eventObject pageFormState =
             pageFormState
 
 
+setField : { formId : String, name : String, value : String } -> PageFormState -> PageFormState
+setField info pageFormState =
+    pageFormState
+        |> Dict.update info.formId
+            (\previousValue_ ->
+                let
+                    previousValue : FormState
+                    previousValue =
+                        previousValue_
+                            |> Maybe.withDefault Dict.empty
+                in
+                previousValue
+                    |> Dict.update info.name
+                        (\previousFieldValue_ ->
+                            let
+                                previousFieldValue : FieldState
+                                previousFieldValue =
+                                    previousFieldValue_
+                                        |> Maybe.withDefault { value = "", status = NotVisited }
+                            in
+                            { previousFieldValue | value = info.value }
+                                |> Just
+                        )
+                    |> Just
+            )
+
+
 updateForm : FieldEvent -> FormState -> FormState
 updateForm fieldEvent formState =
     formState

src/Pages/Internal/Platform.elm

@@ -303,6 +303,7 @@ type Msg userMsg pageData actionData sharedData errorPage
     = LinkClicked Browser.UrlRequest
     | UrlChanged Url
     | UserMsg (Pages.Msg.Msg userMsg)
+    | SetField { formId : String, name : String, value : String }
     | UpdateCacheAndUrlNew Bool Url (Maybe userMsg) (Result Http.Error ( Url, ResponseSketch pageData actionData sharedData ))
     | FetcherComplete Int (Result Http.Error (Maybe userMsg))
     | FetcherStarted FormDecoder.FormData
@@ -381,6 +382,11 @@ update config appMsg model =
                     , BrowserLoadUrl href
                     )
 
+        SetField info ->
+            ( { model | pageFormState = Pages.Form.setField info model.pageFormState }
+            , NoEffect
+            )
+
         UrlChanged url ->
             ( { model
                 -- update the URL in case query params or fragment changed
@@ -746,6 +752,7 @@ perform config model effect =
                                     startFetcher options model
                             , fromPageMsg = Pages.Msg.UserMsg >> UserMsg
                             , key = key
+                            , setField = \info -> Task.succeed (SetField info) |> Task.perform identity
                             }
 
                 Nothing ->

src/Pages/ProgramConfig.elm

@@ -114,6 +114,7 @@ type alias ProgramConfig userMsg userModel route pageData actionData sharedData
         , fromPageMsg : userMsg -> mappedMsg
         , runFetcher : Pages.Fetcher.Fetcher userMsg -> Cmd mappedMsg
         , key : Browser.Navigation.Key
+        , setField : { formId : String, name : String, value : String } -> Cmd mappedMsg
         }
         -> effect
         -> Cmd mappedMsg