Merge pull request #591 from hpi-studyu/issue/564-future-proof-deseri…

…alization-with-exceptions-v2-hig

refactor: improve return type of publishedPublicStudies()

app/lib/screens/study/onboarding/study_selection.dart

@@ -91,23 +91,24 @@ class StudySelectionScreen extends StatelessWidget {
                 ),
               ),
               Expanded(
-                child: RetryFutureBuilder<ExtractingFailedException<Study>>(
+                child: RetryFutureBuilder<ExtractionResult<Study>>(
                   tryFunction: () async => Study.publishedPublicStudies(),
-                  successBuilder: (BuildContext context, ExtractingFailedException<Study>? studies) {
-                    if (studies!.notExtracted.isNotEmpty) {
-                      debugPrint('${studies.notExtracted.length} studies could not be extracted.');
+                  successBuilder: (BuildContext context, ExtractionResult<Study>? extractionResult) {
+                    final studies = extractionResult!.extracted;
+                    if (extractionResult is ExtractionFailedException<Study>) {
+                      debugPrint('${extractionResult.notExtracted.length} studies could not be extracted.');
                       ScaffoldMessenger.of(context).showSnackBar(
                         SnackBar(
                           content: Text(AppLocalizations.of(context)!.study_selection_hidden_studies),
                         ),
                       );
                     }
                     return ListView.builder(
-                      itemCount: studies.extracted.length,
+                      itemCount: studies.length,
                       itemBuilder: (context, index) {
-                        final study = studies.extracted[index];
+                        final study = studies[index];
                         return Hero(
-                          tag: 'study_tile_${studies.extracted[index].id}',
+                          tag: 'study_tile_${studies[index].id}',
                           child: Material(
                             child: StudyTile.fromStudy(
                               study: study,

core/lib/src/models/tables/study.dart

@@ -167,22 +167,19 @@ class Study extends SupabaseObjectFunctions<Study> implements Comparable<Study>
       );
 
   // ['id', 'title', 'description', 'published', 'icon_name', 'results', 'schedule']
-  static Future<ExtractingFailedException<Study>> publishedPublicStudies() async {
-    List<Study> extractedStudies;
-    List<JsonWithError> notExtracted = [];
+  static Future<ExtractionResult<Study>> publishedPublicStudies() async {
+    ExtractionResult<Study> result;
     try {
       final response = await env.client.from(tableName).select().eq('participation', 'open');
-      extractedStudies = SupabaseQuery.extractSupabaseList<Study>(List<Map<String, dynamic>>.from(response));
-    } on ExtractingFailedException<Study> catch (error) {
-      // If some records could not be extracted, catch the exception and
-      // return the extracted records and the faulty records
-      extractedStudies = error.extracted;
-      notExtracted = error.notExtracted;
+      final extracted = SupabaseQuery.extractSupabaseList<Study>(List<Map<String, dynamic>>.from(response));
+      result = ExtractionSuccess<Study>(extracted);
+    } on ExtractionFailedException<Study> catch (error) {
+      result = error;
     } catch (error, stacktrace) {
       SupabaseQuery.catchSupabaseException(error, stacktrace);
       rethrow;
     }
-    return ExtractingFailedException<Study>(extractedStudies, notExtracted);
+    return result;
   }
 
   bool isOwner(User? user) => user != null && userId == user.id;

core/lib/src/util/supabase_object.dart

@@ -79,7 +79,7 @@ class SupabaseQuery {
   }
 
   /// Extracts a list of SupabaseObjects from a response.
-  /// If some records could not be extracted, [ExtractedSupabaseListResult] is
+  /// If some records could not be extracted, [ExtractionFailedException] is
   /// thrown containing the extracted records and the faulty records.
   static List<T> extractSupabaseList<T extends SupabaseObject>(
     List<Map<String, dynamic>> response,
@@ -99,7 +99,7 @@ class SupabaseQuery {
     if (notExtracted.isNotEmpty) {
       // If some records could not be extracted, we throw an exception
       // with the extracted records and the faulty records
-      throw ExtractingFailedException(extracted, notExtracted);
+      throw ExtractionFailedException(extracted, notExtracted);
     }
     return extracted;
   }
@@ -138,15 +138,20 @@ extension PrimaryKeyFilterBuilder on PostgrestFilterBuilder {
   }
 }
 
-abstract class IExtractingFailedException<T> implements Exception {
-  const IExtractingFailedException(this.extracted, this.notExtracted);
-
+sealed class ExtractionResult<T> {
   final List<T> extracted;
-  final List<JsonWithError> notExtracted;
+
+  ExtractionResult(this.extracted);
 }
 
-class ExtractingFailedException<T> extends IExtractingFailedException<T> {
-  ExtractingFailedException(super.extracted, super.notExtracted);
+class ExtractionSuccess<T> extends ExtractionResult<T> {
+  ExtractionSuccess(super.extracted);
+}
+
+class ExtractionFailedException<T> extends ExtractionResult<T> implements Exception {
+  final List<JsonWithError> notExtracted;
+
+  ExtractionFailedException(super.extracted, this.notExtracted);
 }
 
 class JsonWithError {