[native_assets_cli] Validate conditionally required fields (#2126)

Closes: #1826

This PR adds the final step to the generated syntax validation: conditionally required fields:

1. If target OS is `x`, then require `x` config in code config.
2. If target OS is `windows`, then require `windows` in the c compiler config (more info #1913).
3. If link mode is dynamic library bundled or static library, then require a file in a code asset.

We could consider trying to nest the fields under the condition, but that has other downsides:

RE 1: Then the OS is no longer an enum usable in the code-asset as OS field. (We could consider this if we remove the OS/arch from code asset outputs. We should be able to do this due to the code config always having a single OS and architecture anyway. #2127)
RE 2: That would mean the compiler config would be split over two places. `input.config.code.cCompiler` and `inputconfig.code.windows.cCompiler`. Maybe that's better? Maybe not?
RE 3: Treating a group of files in assets would then become `input.assets.code.switch( ... )` instead of simply `input.assets.code.map((a) => a.file)`. Maybe that's okay because we don't often use files in such way anyway?

WDYT @mosuem @HosseinYousefi?

(I'd probably do any of those refactorings in follow up PRs.)

Author: dcharkes

pkgs/json_syntax_generator/lib/src/generator/helper_library.dart

@@ -203,6 +203,18 @@ class JsonReader {
     return "Unexpected value '$value' (${value.runtimeType}) for '$pathString'."
         ' Expected a $expectedType.';
   }
+
+  /// Traverses a JSON path, returns `null` if the path cannot be traversed.
+  Object? tryTraverse(List<String> path) {
+    Object? json = this.json;
+    for (final key in path) {
+      if (json is! Map<String, Object?>) {
+        return null;
+      }
+      json = json[key];
+    }
+    return json;
+  }
 }
 
 extension on Map<String, Object?> {

pkgs/json_syntax_generator/lib/src/generator/normal_class_generator.dart

@@ -34,6 +34,7 @@ class $className $extendsString {
     buffer.writeln(_generateSetupMethod());
     buffer.writeln(_generateAccessors());
     buffer.writeln(_generateValidateMethod());
+    buffer.writeln(_generateExtraValidationMethod());
     buffer.writeln(_generateToString());
     buffer.writeln('''
 }
@@ -244,6 +245,7 @@ class $className $extendsString {
     final validateCalls = [
       for (final property in classInfo.properties)
         '...${property.validateName}()',
+      if (classInfo.extraValidation.isNotEmpty) '..._validateExtraRules()',
     ];
     final validateCallsString = validateCalls.join(',\n');
 
@@ -264,6 +266,65 @@ class $className $extendsString {
 ''';
   }
 
+  String _generateExtraValidationMethod() {
+    if (classInfo.extraValidation.isEmpty) return '';
+    final statements =
+        classInfo.extraValidation
+            .map(_generateExtraValidationStatements)
+            .join()
+            .trim();
+    return '''
+  List<String> _validateExtraRules() {
+    final result = <String>[];
+    $statements
+    return result;
+  }
+''';
+  }
+
+  String _generateExtraValidationStatements(
+    ConditionallyRequired extraValidationRule,
+  ) {
+    final path = extraValidationRule.conditionPath;
+    final values = extraValidationRule.conditionValues;
+    final requiredPath = extraValidationRule.requiredPath;
+    final pathString = path.map((e) => "'$e'").join(',');
+    final traverseExpression = '_reader.tryTraverse([$pathString])';
+    final String conditionExpression;
+    if (values.length == 1) {
+      conditionExpression = "$traverseExpression == '${values.single}'";
+    } else {
+      final valuesString = values.map((e) => "'$e'").join(',');
+      conditionExpression = '[$valuesString].contains($traverseExpression)';
+    }
+    if (requiredPath.length == 1) {
+      final jsonKey = requiredPath.single;
+      return """
+    if ($conditionExpression) {
+      result.addAll(_reader.validate<Object>('$jsonKey'));
+    }
+""";
+    } else if (requiredPath.length == 2) {
+      final jsonKey0 = requiredPath[0];
+      final jsonKey1 = requiredPath[1];
+      return """
+    if ($conditionExpression) {
+      final objectErrors = _reader.validate<Map<String, Object?>?>('$jsonKey0');
+      result.addAll(objectErrors);
+      if (objectErrors.isEmpty) {
+        final jsonValue = _reader.get<Map<String, Object?>?>('$jsonKey0');
+        if (jsonValue != null) {
+          final reader = JsonReader(jsonValue, [...path, '$jsonKey0']);
+          result.addAll(reader.validate<Object>('$jsonKey1'));
+        }
+      }
+    }
+""";
+    } else {
+      throw UnimplementedError('Different path lengths not implemented yet.');
+    }
+  }
+
   String _generateToString() {
     final className = classInfo.name;
     return '''

pkgs/json_syntax_generator/lib/src/generator/property_generator.dart

@@ -86,13 +86,13 @@ class PropertyGenerator {
     final classType = classInfo.name;
     final fieldName = property.name;
     final validateName = property.validateName;
-    final required = property.isRequired;
+    final isNullable = property.type.isNullable;
 
     switch (classInfo) {
       case EnumClassInfo():
-        final dartStringType = StringDartType(isNullable: !required);
+        final dartStringType = StringDartType(isNullable: isNullable);
         final earlyReturn =
-            required ? '' : 'if(jsonValue == null) return null;';
+            isNullable ? 'if(jsonValue == null) return null;' : '';
 
         buffer.writeln('''
 $dartType get $fieldName {
@@ -114,8 +114,8 @@ List<String> $validateName() => _reader.validate<$dartStringType>('$jsonKey');
 
       case NormalClassInfo():
         final earlyReturn =
-            required ? '' : 'if(jsonValue == null) return null;';
-        final jsonRead = required ? 'map\$' : 'optionalMap';
+            isNullable ? 'if(jsonValue == null) return null;' : '';
+        final jsonRead = isNullable ? 'optionalMap' : r'map$';
         buffer.writeln('''
 $dartType get $fieldName {
   final jsonValue = _reader.$jsonRead('$jsonKey'); $earlyReturn
@@ -130,27 +130,21 @@ set $setterName($dartType value) {
   $sortOnKey
 }
 ''');
-          if (required) {
-            buffer.writeln('''
-List<String> $validateName() {
-  final mapErrors = _reader.validate<Map<String, Object?>>('$jsonKey');
-  if (mapErrors.isNotEmpty) {
-    return mapErrors;
-  }
-  return $fieldName.validate();
-}
-''');
-          } else {
-            buffer.writeln('''
+          final mapType = MapDartType(
+            valueType: const ObjectDartType(isNullable: true),
+            isNullable: dartType.isNullable,
+          );
+          final questionMark = isNullable ? '?' : '';
+          final orEmptyList = isNullable ? ' ?? []' : '';
+          buffer.writeln('''
 List<String> $validateName() {
-  final mapErrors = _reader.validate<Map<String, Object?>?>('$jsonKey');
+  final mapErrors = _reader.validate<$mapType>('$jsonKey');
   if (mapErrors.isNotEmpty) {
     return mapErrors;
   }
-  return $fieldName?.validate() ?? [];
+  return $fieldName$questionMark.validate() $orEmptyList;
 }
 ''');
-          }
         }
     }
   }
@@ -186,8 +180,8 @@ List<String> $validateName() => _reader.validate<$dartType>('$jsonKey');
     String setterName,
     String sortOnKey,
   ) {
-    if (property.isRequired) {
-      throw UnimplementedError('Expected an optional property.');
+    if (!property.type.isNullable) {
+      throw UnimplementedError('Expected a nullable property.');
     }
     final fieldName = property.name;
     final validateName = property.validateName;
@@ -301,12 +295,12 @@ List<String> $validateName() => _reader.validateOptionalMap('$jsonKey');
     final validateName = property.validateName;
     final itemType = dartType.itemType;
     final typeName = itemType.toString();
-    final required = property.isRequired;
+    final isNullable = property.type.isNullable;
 
     switch (itemType) {
       case ClassDartType():
-        if (required) {
-          throw UnimplementedError('Expected an optional property.');
+        if (!isNullable) {
+          throw UnimplementedError('Expected a nullable property.');
         }
         buffer.writeln('''
 $dartType get $fieldName {
@@ -351,9 +345,11 @@ List<String> $validateName() {
       case SimpleDartType():
         switch (itemType.typeName) {
           case 'String':
-            final jsonRead = required ? 'stringList' : 'optionalStringList';
+            final jsonRead = isNullable ? 'optionalStringList' : 'stringList';
             final jsonValidate =
-                required ? 'validateStringList' : 'validateOptionalStringList';
+                isNullable
+                    ? 'validateOptionalStringList'
+                    : 'validateStringList';
             final setter = setOrRemove(dartType, jsonKey);
             buffer.writeln('''
 $dartType get $fieldName => _reader.$jsonRead('$jsonKey');
@@ -370,9 +366,9 @@ List<String> $validateName() => _reader.$jsonValidate('$jsonKey');
             throw UnimplementedError(itemType.toString());
         }
       case UriDartType():
-        final jsonRead = required ? 'pathList' : 'optionalPathList';
+        final jsonRead = isNullable ? 'optionalPathList' : 'pathList';
         final jsonValidate =
-            required ? 'validatePathList' : 'validateOptionalPathList';
+            isNullable ? 'validateOptionalPathList' : 'validatePathList';
         final setter = setOrRemove(dartType, jsonKey, '.toJson()');
         buffer.writeln('''
 $dartType get $fieldName => _reader.$jsonRead('$jsonKey');
@@ -399,9 +395,9 @@ List<String> $validateName() => _reader.$jsonValidate('$jsonKey');
   ) {
     final fieldName = property.name;
     final validateName = property.validateName;
-    final required = property.isRequired;
-    final jsonRead = required ? r'path$' : 'optionalPath';
-    final jsonValidate = required ? r'validatePath' : 'validateOptionalPath';
+    final isNullable = property.type.isNullable;
+    final jsonRead = isNullable ? 'optionalPath' : r'path$';
+    final jsonValidate = isNullable ? 'validateOptionalPath' : 'validatePath';
     final setter = setOrRemove(dartType, jsonKey, '.toFilePath()');
     buffer.writeln('''
 $dartType get $fieldName => _reader.$jsonRead('$jsonKey');

pkgs/json_syntax_generator/lib/src/model/class_info.dart

@@ -43,12 +43,15 @@ class NormalClassInfo extends ClassInfo {
   bool get isTaggedUnion =>
       taggedUnionProperty != null || taggedUnionValue != null;
 
+  final List<ConditionallyRequired> extraValidation;
+
   NormalClassInfo({
     required super.name,
     this.superclass,
     required this.properties,
     this.taggedUnionProperty,
     this.taggedUnionValue,
+    this.extraValidation = const [],
   }) : super() {
     superclass?.subclasses.add(this);
     if (taggedUnionValue != null) {
@@ -61,6 +64,9 @@ class NormalClassInfo extends ClassInfo {
     final propertiesString = properties
         .map((p) => indentLines(p.toString(), level: 2))
         .join(',\n');
+    final extraValidationString = extraValidation
+        .map((p) => indentLines(p.toString(), level: 2))
+        .join('\n');
     return '''
 $runtimeType(
   name: $name,
@@ -71,10 +77,39 @@ $propertiesString
   ],
   taggedUnionProperty: $taggedUnionProperty,
   taggedUnionValue: $taggedUnionValue,
+  extraValidation: [
+$extraValidationString
+  ],
 )''';
   }
 }
 
+/// The property [requiredPath] is required if some [conditionPath] has a value
+/// in [conditionValues].
+///
+/// This class is special cased to cover the uses cases seen so far. If
+/// different types of conditionals are needed, this class should probably be
+/// extended to cover some arbitrary expression.
+class ConditionallyRequired {
+  final List<String> conditionPath;
+  final List<String> conditionValues;
+  final List<String> requiredPath;
+
+  const ConditionallyRequired({
+    required this.conditionPath,
+    required this.conditionValues,
+    required this.requiredPath,
+  });
+
+  @override
+  String toString() => '''
+ConditionallyRequired(
+  path: $conditionPath,
+  values: $conditionValues,
+  required: $requiredPath,
+)''';
+}
+
 class EnumClassInfo extends ClassInfo {
   final List<EnumValue> enumValues;
   final bool isOpen;

pkgs/json_syntax_generator/lib/src/model/property_info.dart

@@ -35,8 +35,6 @@ class PropertyInfo {
   /// meal. See [SchemaAnalyzer.publicSetters].
   final bool setterPrivate;
 
-  bool get isRequired => !type.isNullable;
-
   PropertyInfo({
     required this.name,
     required this.jsonKey,
@@ -53,7 +51,6 @@ PropertyInfo(
   type: $type,
   isOverride: $isOverride,
   setterPrivate: $setterPrivate,
-  isRequired: $isRequired,
 )''';
 }