Add translation fallback handling for unknown keys

src/app/app.module.ts

@@ -15,7 +15,7 @@ import {StatusBar} from "@ionic-native/status-bar";
 import {StreamingMedia} from "@ionic-native/streaming-media";
 import {Toast} from "@ionic-native/toast";
 import {IonicApp, IonicErrorHandler, IonicModule, ModalController, NavController, Platform} from "ionic-angular";
-import {TranslateModule, TranslateService} from "ng2-translate/ng2-translate";
+import {TranslateModule, TranslateService, MissingTranslationHandler} from "ng2-translate/ng2-translate";
 import {TranslateLoader, TranslateStaticLoader} from "ng2-translate/src/translate.service";
 import {OPEN_LEARNPLACE_ACTION_FACTORY, OpenLearnplaceAction, OpenLearnplaceActionFunction} from "../actions/open-learnplace-action";
 import {OPEN_OBJECT_IN_ILIAS_ACTION_FACTORY, OpenObjectInILIASAction} from "../actions/open-object-in-ilias-action";
@@ -87,6 +87,7 @@ import {DiagnosticUtil} from "../services/device/hardware-features/diagnostics.u
 import {Hardware} from "../services/device/hardware-features/hardware-feature.service";
 import {FileService} from "../services/file.service";
 import {FooterToolbarService} from "../services/footer-toolbar.service";
+import {PegasusMissingTranslationHandler} from "../services/language/translation-missing-handler";
 import {DEFAULT_LINK_BUILDER, DefaultLinkBuilder, DefaultLinkBuilderImpl} from "../services/link/default.builder";
 import {LINK_BUILDER, LinkBuilderImpl} from "../services/link/link-builder.service";
 import {
@@ -459,7 +460,8 @@ import {HTTP} from "@ionic-native/http";
 
     IonicErrorHandler,
     {provide: ErrorHandler, useClass: PegasusErrorHandler},
-      <ClassProvider>{provide: XhrFactory, useClass: PegasusXhrFactory, multi: false}
+      <ClassProvider>{provide: XhrFactory, useClass: PegasusXhrFactory, multi: false},
+      <ClassProvider>{provide: MissingTranslationHandler, useClass: PegasusMissingTranslationHandler, multi: false}
   ],
   exports: [
     TranslateModule

src/services/language/translation-missing-handler.ts

@@ -0,0 +1,36 @@
+import {MissingTranslationHandler, MissingTranslationHandlerParams, TranslateService} from "ng2-translate";
+import {Injectable} from "@angular/core";
+import {Logger} from "../logging/logging.api";
+import {Logging} from "../logging/logging.service";
+
+/**
+ * Fallback handler for translation.
+ * The handler will check if the missing translation is due to a unknown type which may happens with ILIAS plugins.
+ * If the key do not start with the "object_type" namespace the missing key is return as translation in order to
+ * indicate which variable is missing.
+ *
+ * It is not possible to translate a string within this handler due to the fact that the
+ * TranslationService is depending on the MissingTranslation handler.
+ *
+ * @author Nicolas Schaefli <[email protected]>
+ * @version 1.0.0
+ * @since v2.0.1
+ */
+@Injectable()
+export class PegasusMissingTranslationHandler extends MissingTranslationHandler {
+
+    private static readonly OBJECT_TYPE_KEY: string = "object_type.";
+    private readonly log: Logger = Logging.getLogger(PegasusMissingTranslationHandler.name);
+
+    handle(params: MissingTranslationHandlerParams): string {
+
+        // check if we got a object_type which indicates that we got a unknown object from ILIAS most likely a plugin
+        if(params.key.startsWith(PegasusMissingTranslationHandler.OBJECT_TYPE_KEY) === true) {
+            this.log.warn(() => `No ILIAS object translation found for "${params.key}" fallback to "Object" translation.`);
+            return "Object";
+        }
+
+        this.log.warn(() => `Missing translation falling back to key "${params.key}"`);
+        return params.key;
+    }
+}