Handle port-data-source errors in BackendTasks.

generator/src/request-cache.js

@@ -75,20 +75,60 @@ function lookupOrPerform(portsFile, mode, rawRequest, hasFsAccess, useCache) {
 
           if (!portBackendTask[portName]) {
             if (portBackendTaskImportError === null) {
-              throw `BackendTask.Port.send "${portName}" was called, but I couldn't find a function with that name in the port definitions file. Is it exported correctly?`;
+              resolve({
+                kind: "response-json",
+                value: jsonResponse({
+                  "elm-pages-internal-error": "PortNotDefined",
+                }),
+              });
             } else if (portBackendTaskImportError === "missing") {
-              throw `BackendTask.Port.send "${portName}" was called, but I couldn't find the port definitions file. Be sure to create a 'port-data-source.ts' or 'port-data-source.js' file and maybe restart the dev server.`;
+              resolve({
+                kind: "response-json",
+                value: jsonResponse({
+                  "elm-pages-internal-error": "MissingPortsFile",
+                }),
+              });
             } else {
-              throw `BackendTask.Port.send "${portName}" was called, but I couldn't import the port definitions file, because of this exception: \`${portBackendTaskImportError}\` Are there syntax errors or expections thrown during import?`;
+              resolve({
+                kind: "response-json",
+                value: jsonResponse({
+                  "elm-pages-internal-error": "ErrorInPortsFile",
+                  error:
+                    (portBackendTaskImportError &&
+                      portBackendTaskImportError.stack) ||
+                    "",
+                }),
+              });
             }
           } else if (typeof portBackendTask[portName] !== "function") {
-            throw `BackendTask.Port.send "${portName}" was called, but it is not a function. Be sure to export a function with that name from port-data-source.js`;
+            resolve({
-          }
+              kind: "response-json",
+              value: jsonResponse({
+                "elm-pages-internal-error": "ExportIsNotFunction",
+                error: typeof portBackendTask[portName],
+              }),
+            });
+          } else {
+            try {
+              const portFunctionResult = await portBackendTask[portName](input);
               await fs.promises.writeFile(
                 responsePath,
-            JSON.stringify(jsonResponse(await portBackendTask[portName](input)))
+                JSON.stringify(jsonResponse(portFunctionResult))
               );
-          resolve({ kind: "cache-response-path", value: responsePath });
+              resolve({
+                kind: "cache-response-path",
+                value: responsePath,
+              });
+            } catch (portCallError) {
+              resolve({
+                kind: "response-json",
+                value: jsonResponse({
+                  "elm-pages-internal-error": "PortCallError",
+                  error: portCallError,
+                }),
+              });
+            }
+          }
         } catch (error) {
           console.trace(error);
           reject({

src/BackendTask/Port.elm

@@ -15,7 +15,7 @@ import BackendTask
 import BackendTask.Http
 import BackendTask.Internal.Request
 import Exception exposing (Catchable)
-import Json.Decode exposing (Decoder)
+import Json.Decode as Decode exposing (Decoder)
 import Json.Encode as Encode
 import TerminalText
 
@@ -92,24 +92,111 @@ get portName input decoder =
                 ]
                 |> BackendTask.Http.jsonBody
         , expect =
-            decoder
+            Decode.oneOf
-                |> BackendTask.Http.expectJson
+                [ Decode.field "elm-pages-internal-error" Decode.string
-        }
+                    |> Decode.andThen
-        |> BackendTask.onError
+                        (\errorKind ->
-            (\_ ->
+                            if errorKind == "PortNotDefined" then
-                BackendTask.fail
+                                Exception.Catchable (PortNotDefined { name = portName })
-                    (Exception.Catchable Error
                                     { title = "Port Error"
                                     , body =
-                            [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get."
+                                        [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I expected to find a port named `"
+                                        , TerminalText.yellow portName
+                                        , TerminalText.text "` but I couldn't find it. Is the function exported in your port-data-source file?"
+                                        ]
+                                            |> TerminalText.toString
+                                    }
+                                    |> Decode.succeed
+
+                            else if errorKind == "ExportIsNotFunction" then
+                                Decode.field "error" Decode.string
+                                    |> Decode.maybe
+                                    |> Decode.map (Maybe.withDefault "")
+                                    |> Decode.map
+                                        (\incorrectPortType ->
+                                            Exception.Catchable ExportIsNotFunction
+                                                { title = "Port Error"
+                                                , body =
+                                                    [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I found an export called `"
+                                                    , TerminalText.yellow portName
+                                                    , TerminalText.text "` but I expected its type to be function, but instead its type was: "
+                                                    , TerminalText.red incorrectPortType
                                                     ]
                                                         |> TerminalText.toString
                                                 }
                                         )
+
+                            else if errorKind == "MissingPortsFile" then
+                                Exception.Catchable MissingPortsFile
+                                    { title = "Port Error"
+                                    , body =
+                                        [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I couldn't find your port-data-source file. Be sure to create a 'port-data-source.ts' or 'port-data-source.js' file."
+                                        ]
+                                            |> TerminalText.toString
+                                    }
+                                    |> Decode.succeed
+
+                            else if errorKind == "ErrorInPortsFile" then
+                                Decode.field "error" Decode.string
+                                    |> Decode.maybe
+                                    |> Decode.map (Maybe.withDefault "")
+                                    |> Decode.map
+                                        (\errorMessage ->
+                                            Exception.Catchable
+                                                ErrorInPortsFile
+                                                { title = "Port Error"
+                                                , body =
+                                                    [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I couldn't import the port definitions file, because of this exception:\n\n"
+                                                    , TerminalText.red errorMessage
+                                                    , TerminalText.text "\n\nAre there syntax errors or exceptions thrown during import?"
+                                                    ]
+                                                        |> TerminalText.toString
+                                                }
                                         )
 
+                            else if errorKind == "PortCallError" then
+                                Decode.field "error" Decode.value
+                                    |> Decode.maybe
+                                    |> Decode.map (Maybe.withDefault Encode.null)
+                                    |> Decode.map
+                                        (\portCallError ->
+                                            Exception.Catchable
+                                                (PortCallError portCallError)
+                                                { title = "Port Error"
+                                                , body =
+                                                    [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I couldn't import the port definitions file, because of this exception:\n\n"
+                                                    , TerminalText.red (Encode.encode 2 portCallError)
+                                                    , TerminalText.text "\n\nAre there syntax errors or exceptions thrown during import?"
+                                                    ]
+                                                        |> TerminalText.toString
+                                                }
+                                        )
+
+                            else
+                                Exception.Catchable ErrorInPortsFile
+                                    { title = "Port Error"
+                                    , body =
+                                        [ TerminalText.text "Something went wrong in a call to BackendTask.Port.get. I expected to find a port named `"
+                                        , TerminalText.yellow portName
+                                        , TerminalText.text "`."
+                                        ]
+                                            |> TerminalText.toString
+                                    }
+                                    |> Decode.succeed
+                        )
+                    |> Decode.map Err
+                , decoder |> Decode.map Ok
+                ]
+                |> BackendTask.Http.expectJson
+        }
+        |> BackendTask.andThen BackendTask.fromResult
+
 
 {-| -}
 type Error
-    = -- TODO include additional context about error or better name to reflect the error state
+    = Error
-      Error
+    | ErrorInPortsFile
+    | MissingPortsFile
+    | PortNotDefined { name : String }
+    | PortCallError Decode.Value
+    | ExportIsNotFunction