Update examples to use ErrorPage, and add to NoContractViolations.

examples/base-path/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

examples/docs/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

examples/end-to-end/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

examples/escaping/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

examples/escaping/dist/escaping/index.html

@@ -17,7 +17,7 @@
       content="black-translucent"
     />
         <link rel="canonical" href="https://elm-pages.com/escaping" />    <meta name="description" content="These quotes should be escaped &quot;ESCAPE THIS&quot;, and so should &lt;CARETS&gt;" />    <meta property="og:image" content="TODO" />    <meta property="og:image:secure_url" content="TODO" />    <meta property="og:image:alt" content="elm-pages logo" />    <meta property="og:title" content="TODO title" />    <meta property="og:url" content="https://elm-pages.com/escaping" />    <meta property="og:description" content="These quotes should be escaped &quot;ESCAPE THIS&quot;, and so should &lt;CARETS&gt;" />    <meta property="og:site_name" content="elm-pages" />    <meta property="twitter:card" content="summary" />    <meta property="twitter:title" content="TODO title" />    <meta property="twitter:description" content="These quotes should be escaped &quot;ESCAPE THIS&quot;, and so should &lt;CARETS&gt;" />    <meta property="twitter:image" content="TODO" />    <meta property="twitter:image:alt" content="elm-pages logo" />    <meta property="og:type" content="website" />    <link rel="icon" sizes="32x32" type="image/png" href="https://res.cloudinary.com/dillonkearns/image/upload/c_pad,w_32,h_32,q_auto,f_png/v1603234028/elm-pages/elm-pages-icon" />    <link rel="icon" sizes="16x16" type="image/png" href="https://res.cloudinary.com/dillonkearns/image/upload/c_pad,w_16,h_16,q_auto,f_png/v1603234028/elm-pages/elm-pages-icon" />    <link rel="apple-touch-icon" sizes="180x180" href="https://res.cloudinary.com/dillonkearns/image/upload/c_pad,w_180,h_180,q_auto,f_png/v1603234028/elm-pages/elm-pages-icon" />    <link rel="apple-touch-icon" sizes="192x192" href="https://res.cloudinary.com/dillonkearns/image/upload/c_pad,w_192,h_192,q_auto,f_png/v1603234028/elm-pages/elm-pages-icon" />    <link rel="sitemap" type="application/xml" href="/sitemap.xml" />
-                  <script id="__ELM_PAGES_BYTES_DATA__" type="application/octet-stream">AAGEPHNjcmlwdD48L3NjcmlwdD4gaXMgdW5zYWZlIGluIEpTT04gdW5sZXNzIGl0IGlzIGVzY2FwZWQgcHJvcGVybHku</script>
+                  <script id="__ELM_PAGES_BYTES_DATA__" type="application/octet-stream">AQGEPHNjcmlwdD48L3NjcmlwdD4gaXMgdW5zYWZlIGluIEpTT04gdW5sZXNzIGl0IGlzIGVzY2FwZWQgcHJvcGVybHku</script>
     <script type="module" crossorigin src="/assets/index.a677aaa6.js"></script>
     <link rel="stylesheet" href="/assets/index.b0f41fb5.css">
   </head>

examples/hello/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

examples/routing/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

generator/template/app/ErrorPage.elm

@@ -0,0 +1,38 @@
+module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+
+import Html exposing (Html)
+
+
+type ErrorPage
+    = NotFound
+    | InternalError String
+
+
+notFound : ErrorPage
+notFound =
+    NotFound
+
+
+internalError : String -> ErrorPage
+internalError =
+    InternalError
+
+
+view : ErrorPage -> { body : Html msg, title : String }
+view error =
+    { body =
+        Html.div []
+            [ Html.text "Hi! This is a NotFound error"
+            ]
+    , title = "Error"
+    }
+
+
+statusCode : ErrorPage -> number
+statusCode error =
+    case error of
+        NotFound ->
+            404
+
+        InternalError _ ->
+            500

src/Pages/Internal/Platform.elm

@@ -439,8 +439,7 @@ update config appMsg model =
                     (updateResult
                         |> Result.mapError
                             (\_ ->
-                                --"Http error"
-                                Debug.todo "HTTP ERROR"
+                                config.internalError "Http error"
                             )
                     )
                     model.pageData

src/Pages/Review/NoContractViolations.elm

@@ -112,6 +112,7 @@ coreModules =
     Set.fromList
         [ [ "Api" ]
         , [ "Effect" ]
+        , [ "ErrorPage" ]
         , [ "Shared" ]
         , [ "Site" ]
         , [ "View" ]
@@ -123,6 +124,7 @@ coreModulesAndExports =
     Dict.fromList
         [ ( [ "Api" ], [ "routes" ] )
         , ( [ "Effect" ], [ "Effect", "batch", "fromCmd", "map", "none", "perform" ] )
+        , ( [ "ErrorPage" ], [ "ErrorPage", "notFound", "internalError", "view", "statusCode" ] )
         , ( [ "Shared" ], [ "Data", "Model", "Msg", "template" ] )
         , ( [ "Site" ], [ "config" ] )
         , ( [ "View" ], [ "View", "map", "placeholder" ] )

tests/Pages/Review/NoContractViolationsTest.elm

@@ -190,6 +190,7 @@ config =
                           , details =
                                 [ "Api"
                                 , "Effect"
+                                , "ErrorPage"
                                 , "Shared"
                                 , "View"
                                 ]
@@ -220,7 +221,9 @@ invalid = Debug.todo ""
 """
                 , """module Effect exposing (invalid)
 invalid = Debug.todo ""
-
+"""
+                , """module ErrorPage exposing (invalid)
+invalid = Debug.todo ""
 """
                 , """module Shared exposing (invalid)
 invalid = Debug.todo ""
@@ -254,6 +257,16 @@ invalid = Debug.todo ""
                                 }
                             ]
                           )
+                        , ( "ErrorPage"
+                          , [ Review.Test.error
+                                { message = "A core elm-pages module needs to expose something"
+                                , details =
+                                    [ "The ErrorPage module must expose `ErrorPage`, `internalError`, `notFound`, `statusCode`, `view`"
+                                    ]
+                                , under = "exposing (invalid)"
+                                }
+                            ]
+                          )
                         , ( "Shared"
                           , [ Review.Test.error
                                 { message = "A core elm-pages module needs to expose something"
@@ -301,6 +314,9 @@ routes = Debug.todo ""
 """
     , """module Effect exposing (Effect(..), batch, fromCmd, map, none, perform)
 routes = Debug.todo ""
+"""
+    , """module ErrorPage exposing (ErrorPage(..), internalError, notFound, statusCode, view)
+routes = Debug.todo ""
 """
     , """module Shared exposing (Data, Model, Msg, template)
 routes = Debug.todo ""

tests/StaticHttpRequestsTests.elm

@@ -444,7 +444,7 @@ startLowLevel apiRoutes staticHttpCache pages =
                 Nothing ->
                     Debug.todo "Error - no pages"
 
-        config : ProgramConfig Msg () Route () () Effect mappedMsg
+        config : ProgramConfig Msg () Route () () Effect mappedMsg ()
         config =
             { toJsPort = toJsPort
             , fromJsPort = fromJsPort
@@ -514,6 +514,14 @@ startLowLevel apiRoutes staticHttpCache pages =
             , globalHeadTags = Nothing
             , perform = \_ _ _ -> Cmd.none
             , cmdToEffect = \_ -> Effect.NoEffect
+            , errorStatusCode = \_ -> 404
+            , notFoundPage = ()
+            , internalError = \_ -> ()
+            , errorView =
+                \() ->
+                    { title = "Error"
+                    , body = Html.text ""
+                    }
             }
 
         encodedFlags : Encode.Value
@@ -591,7 +599,7 @@ startWithRoutes :
     -> ProgramTest (Model Route) Msg Effect
 startWithRoutes pageToLoad staticRoutes staticHttpCache pages =
     let
-        config : ProgramConfig Msg () Route () () Effect mappedMsg
+        config : ProgramConfig Msg () Route () () Effect mappedMsg ()
         config =
             { toJsPort = toJsPort
             , fromJsPort = fromJsPort
@@ -671,6 +679,14 @@ startWithRoutes pageToLoad staticRoutes staticHttpCache pages =
             , globalHeadTags = Nothing
             , perform = \_ _ _ -> Cmd.none
             , cmdToEffect = \_ -> Effect.NoEffect
+            , errorStatusCode = \_ -> 404
+            , notFoundPage = ()
+            , internalError = \_ -> ()
+            , errorView =
+                \() ->
+                    { title = "Error"
+                    , body = Html.text ""
+                    }
             }
 
         encodedFlags : Encode.Value