fix: context enums should use fallback

slang/lib/builder/builder/translation_model_builder.dart

@@ -26,9 +26,12 @@ class BuildModelResult {
 class TranslationModelBuilder {
   /// Builds the i18n model for ONE locale
   ///
-  /// The map must be of type Map<String, dynamic> and all children may of type
+  /// The [map] must be of type Map<String, dynamic> and all children may of type
   /// String, num, List<dynamic> or Map<String, dynamic>.
   ///
+  /// If [baseData] is set and [BuildModelConfig.fallbackStrategy] is [FallbackStrategy.baseLocale],
+  /// then the base translations will be added to contexts where the translation is missing.
+  ///
   /// [handleLinks] can be set false to ignore links and leave them as is
   /// e.g. ${_root.greet(name: name} will be ${_root.greet}
   /// This is used for "Translation Overrides" where the links are resolved
@@ -40,13 +43,28 @@ class TranslationModelBuilder {
   static BuildModelResult build({
     required BuildModelConfig buildConfig,
     required Map<String, dynamic> map,
+    BuildModelResult? baseData,
     bool handleLinks = true,
     bool shouldEscapeText = true,
     required String localeDebug,
   }) {
     // flat map for leaves (TextNode, PluralNode, ContextNode)
     final Map<String, LeafNode> leavesMap = {};
 
+    // base contexts to be used for fallback
+    final Map<String, PopulatedContextType>? baseContexts = baseData == null ||
+            baseData.contexts.isEmpty ||
+            buildConfig.fallbackStrategy == FallbackStrategy.none
+        ? null
+        : {
+            for (final c in baseData.contexts)
+              c.enumName: PopulatedContextType(
+                enumName: c.enumName,
+                enumValues: c.enumValues,
+                generateEnum: c.generateEnum,
+              ),
+          };
+
     final contextCollection = {
       for (final context in buildConfig.contexts) context.enumName: context,
     };
@@ -66,6 +84,8 @@ class TranslationModelBuilder {
       keyCase: buildConfig.keyCase,
       leavesMap: leavesMap,
       contextCollection: contextCollection,
+      baseData: baseData,
+      baseContexts: baseContexts,
       shouldEscapeText: shouldEscapeText,
     );
 
@@ -213,6 +233,8 @@ Map<String, Node> _parseMapNode({
   required CaseStyle? keyCase,
   required Map<String, LeafNode> leavesMap,
   required Map<String, ContextType> contextCollection,
+  required BuildModelResult? baseData,
+  required Map<String, PopulatedContextType>? baseContexts,
   required bool shouldEscapeText,
 }) {
   final Map<String, Node> resultNodeTree = {};
@@ -284,6 +306,8 @@ Map<String, Node> _parseMapNode({
           keyCase: config.keyCase,
           leavesMap: leavesMap,
           contextCollection: contextCollection,
+          baseData: baseData,
+          baseContexts: baseContexts,
           shouldEscapeText: shouldEscapeText,
         );
 
@@ -312,6 +336,8 @@ Map<String, Node> _parseMapNode({
               : config.keyCase,
           leavesMap: leavesMap,
           contextCollection: contextCollection,
+          baseData: baseData,
+          baseContexts: baseContexts,
           shouldEscapeText: shouldEscapeText,
         );
 
@@ -365,6 +391,8 @@ Map<String, Node> _parseMapNode({
               keyCase: config.keyCase,
               leavesMap: leavesMap,
               contextCollection: contextCollection,
+              baseData: baseData,
+              baseContexts: baseContexts,
               shouldEscapeText: shouldEscapeText,
             ).cast<String, RichTextNode>();
           }
@@ -385,6 +413,21 @@ Map<String, Node> _parseMapNode({
               contextCollection[context.enumName] = context;
             }
 
+            if (config.fallbackStrategy == FallbackStrategy.baseLocale ||
+                config.fallbackStrategy ==
+                    FallbackStrategy.baseLocaleEmptyString) {
+              // add base context values if necessary
+              final baseContext = baseContexts?[context.enumName];
+              if (baseContext != null) {
+                digestedMap = _digestContextEntries(
+                  baseTranslation: baseData!.root,
+                  baseContext: baseContext,
+                  path: '$currPath',
+                  entries: digestedMap,
+                );
+              }
+            }
+
             finalNode = ContextNode(
               path: currPath,
               rawPath: currRawPath,
@@ -780,6 +823,39 @@ void _fixEmptyLists({
   });
 }
 
+/// Makes sure that every enum value in [baseContext] is also present in [entries].
+/// If a value is missing, the base translation is used.
+Map<String, TextNode> _digestContextEntries({
+  required ObjectNode baseTranslation,
+  required PopulatedContextType baseContext,
+  required String path,
+  required Map<String, TextNode> entries,
+}) {
+  // Using "late" keyword because we are optimistic that all values are present
+  late ContextNode baseContextNode =
+      _findContextNode(baseTranslation, path.split('.'));
+  return {
+    for (final value in baseContext.enumValues)
+      value: entries[value] ?? baseContextNode.entries[value]!,
+  };
+}
+
+/// Recursively find the [ContextNode] using the given [path].
+ContextNode _findContextNode(ObjectNode node, List<String> path) {
+  final child = node.entries[path[0]];
+  if (path.length == 1) {
+    if (child is ContextNode) {
+      return child;
+    } else {
+      throw 'Parent node is not a ContextNode but a ${node.runtimeType} at path $path';
+    }
+  } else if (child is ObjectNode) {
+    return _findContextNode(child, path.sublist(1));
+  } else {
+    throw 'Cannot find base ContextNode';
+  }
+}
+
 enum _DetectionType {
   classType,
   map,

slang/lib/builder/builder/translation_model_list_builder.dart

@@ -16,22 +16,49 @@ class TranslationModelListBuilder {
   ) {
     final buildConfig = rawConfig.toBuildModelConfig();
 
+    final baseEntry = translationMap.getInternalMap().entries.firstWhere(
+          (entry) => entry.key == rawConfig.baseLocale,
+          orElse: () => throw Exception('Base locale not found'),
+        );
+
+    // Create the base data first.
+    final namespaces = baseEntry.value;
+    final baseResult = TranslationModelBuilder.build(
+      buildConfig: buildConfig,
+      map: rawConfig.namespaces ? namespaces : namespaces.values.first,
+      localeDebug: baseEntry.key.languageTag,
+    );
+
     return translationMap.getInternalMap().entries.map((localeEntry) {
       final locale = localeEntry.key;
       final namespaces = localeEntry.value;
-      final result = TranslationModelBuilder.build(
-        buildConfig: buildConfig,
-        map: rawConfig.namespaces ? namespaces : namespaces.values.first,
-        localeDebug: locale.languageTag,
-      );
+      final base = locale == rawConfig.baseLocale;
+
+      if (base) {
+        // Use the already computed base data
+        return I18nData(
+          base: true,
+          locale: locale,
+          root: baseResult.root,
+          contexts: baseResult.contexts,
+          interfaces: baseResult.interfaces,
+        );
+      } else {
+        final result = TranslationModelBuilder.build(
+          buildConfig: buildConfig,
+          map: rawConfig.namespaces ? namespaces : namespaces.values.first,
+          baseData: baseResult,
+          localeDebug: locale.languageTag,
+        );
 
-      return I18nData(
-        base: rawConfig.baseLocale == locale,
-        locale: locale,
-        root: result.root,
-        contexts: result.contexts,
-        interfaces: result.interfaces,
-      );
+        return I18nData(
+          base: rawConfig.baseLocale == locale,
+          locale: locale,
+          root: result.root,
+          contexts: result.contexts,
+          interfaces: result.interfaces,
+        );
+      }
     }).toList()
       ..sort(I18nData.generationComparator);
   }

slang/lib/builder/model/raw_config.dart

@@ -4,7 +4,7 @@ import 'package:slang/builder/model/i18n_locale.dart';
 import 'package:slang/builder/model/interface.dart';
 import 'package:slang/builder/model/obfuscation_config.dart';
 
-/// represents a build.yaml
+/// represents a build.yaml or a slang.yaml file
 class RawConfig {
   static const String defaultBaseLocale = 'en';
   static const FallbackStrategy defaultFallbackStrategy = FallbackStrategy.none;

slang/test/integration/main/fallback_base_locale_test.dart

@@ -1,5 +1,6 @@
 import 'package:slang/builder/builder/raw_config_builder.dart';
 import 'package:slang/builder/decoder/csv_decoder.dart';
+import 'package:slang/builder/decoder/json_decoder.dart';
 import 'package:slang/builder/generator_facade.dart';
 import 'package:slang/builder/model/enums.dart';
 import 'package:slang/builder/model/i18n_locale.dart';
@@ -13,15 +14,25 @@ void main() {
   late String buildYaml;
   late String expectedOutput;
 
+  late String specialEnInput;
+  late String specialDeInput;
+  late String specialExpectedOutput;
+
   setUp(() {
     compactInput = loadResource('main/csv_compact.csv');
     buildYaml = loadResource('main/build_config.yaml');
     expectedOutput = loadResource(
       'main/_expected_fallback_base_locale.output',
     );
+
+    specialEnInput = loadResource('main/fallback_en.json');
+    specialDeInput = loadResource('main/fallback_de.json');
+    specialExpectedOutput = loadResource(
+      'main/_expected_fallback_base_locale_special.output',
+    );
   });
 
-  test('translation overrides', () {
+  test('fallback with generic integration data', () {
     final parsed = CsvDecoder().decode(compactInput);
 
     final result = GeneratorFacade.generate(
@@ -43,4 +54,25 @@ void main() {
 
     expect(result.joinAsSingleOutput(), expectedOutput);
   });
+
+  test('fallback with special integration data', () {
+    final result = GeneratorFacade.generate(
+      rawConfig: RawConfigBuilder.fromYaml(buildYaml)!.copyWith(
+        fallbackStrategy: FallbackStrategy.baseLocale,
+      ),
+      baseName: 'translations',
+      translationMap: TranslationMap()
+        ..addTranslations(
+          locale: I18nLocale.fromString('en'),
+          translations: JsonDecoder().decode(specialEnInput),
+        )
+        ..addTranslations(
+          locale: I18nLocale.fromString('de'),
+          translations: JsonDecoder().decode(specialDeInput),
+        ),
+      inputDirectoryHint: 'fake/path/integration',
+    );
+
+    expect(result.joinAsSingleOutput(), specialExpectedOutput);
+  });
 }