Add integration test for existing types in drift

drift/test/generated/custom_tables.g.dart

@@ -1853,6 +1853,33 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
     });
   }
 
+  Selectable<MyCustomResultClass> customResult() {
+    return customSelect(
+        'SELECT with_constraints.b, config.sync_state,"config"."config_key" AS "nested_0.config_key", "config"."config_value" AS "nested_0.config_value", "config"."sync_state" AS "nested_0.sync_state", "config"."sync_state_implicit" AS "nested_0.sync_state_implicit","no_ids"."payload" AS "nested_1.payload" FROM with_constraints INNER JOIN config ON config_key = with_constraints.a CROSS JOIN no_ids',
+        variables: [],
+        readsFrom: {
+          withConstraints,
+          config,
+          noIds,
+        }).asyncMap((QueryRow row) async => MyCustomResultClass(
+          row.read<int>('b'),
+          syncState: NullAwareTypeConverter.wrapFromSql(
+              ConfigTable.$convertersyncState,
+              row.readNullable<int>('sync_state')),
+          config: await config.mapFromRow(row, tablePrefix: 'nested_0'),
+          noIds: await noIds.mapFromRow(row, tablePrefix: 'nested_1'),
+          nested: await customSelect('SELECT * FROM no_ids',
+                  variables: [],
+                  readsFrom: {
+                noIds,
+              })
+              .map((QueryRow row) => Buffer(
+                    row.read<Uint8List>('payload'),
+                  ))
+              .get(),
+        ));
+  }
+
   @override
   Iterable<TableInfo<Table, Object?>> get allTables =>
       allSchemaEntities.whereType<TableInfo<Table, Object?>>();

drift/test/generated/data_classes.dart

@@ -1,5 +1,41 @@
+import 'dart:typed_data';
+
+import 'converter.dart';
+import 'custom_tables.dart';
+
 class NoIdRow {
   final List<int> payload;
 
   NoIdRow(this.payload);
 }
+
+class Buffer {
+  Buffer(TypedData payload);
+}
+
+/// The existing result class for the `customResult` query in `tables.drift`
+class MyCustomResultClass {
+  // with_constraints.b
+  final int b;
+
+  // config.sync_state
+  final SyncType? syncState;
+
+  // config.** (drift-generated table row class)
+  final Config config;
+
+  // no_ids.** (custom table row class)
+  final NoIdRow noIds;
+
+  // LIST(SELECT * FROM no_ids). Note that we're replacing the custom table
+  // row class with a custom structure class just for this query.
+  final List<Buffer> nested;
+
+  MyCustomResultClass(
+    this.b, {
+    required this.syncState,
+    required this.config,
+    required this.noIds,
+    required this.nested,
+  });
+}

drift/test/generated/tables.drift

@@ -98,3 +98,14 @@ addConfig: INSERT INTO config $value RETURNING *;
 nested: SELECT defaults.**, LIST(SELECT * FROM with_constraints c WHERE c.b = defaults.b)
   FROM with_defaults defaults
   WHERE a = ?;
+
+customResult WITH MyCustomResultClass:
+  SELECT
+    with_constraints.b,
+    config.sync_state,
+    config.**,
+    no_ids.**,
+    LIST(SELECT * FROM no_ids) AS nested
+  FROM with_constraints
+    INNER JOIN config ON config_key = with_constraints.a
+    CROSS JOIN no_ids;

drift/test/integration_tests/drift_files_integration_test.dart

@@ -172,4 +172,13 @@ void main() {
       );
     });
   }, skip: ifOlderThanSqlite335(sqlite3Version));
+
+  test('can run query with custom result set', () async {
+    await db.withConstraints
+        .insertOne(WithConstraintsCompanion.insert(b: 1, a: Value('key')));
+    await db.noIds.insertOne(NoIdsCompanion.insert(payload: Uint8List(512)));
+
+    final result = await db.customResult().get();
+    print('result');
+  });
 }

drift_dev/lib/src/analysis/resolver/file_analysis.dart

@@ -100,7 +100,8 @@ class FileAnalyzer {
               references: element.references,
               requiredVariables: options.variables);
 
-          result.resolvedQueries[element.id] = analyzer.analyze(element)
+          result.resolvedQueries[element.id] = analyzer.analyze(element,
+              sourceForCustomName: stmt.as)
             ..declaredInDriftFile = true;
 
           for (final error in analyzer.lints) {

drift_dev/lib/src/analysis/resolver/queries/query_analyzer.dart

@@ -25,6 +25,8 @@ class _QueryHandlerContext {
   final String? requestedResultClass;
   final DartType? requestedResultType;
 
+  final DriftTableName? sourceForFixedName;
+
   _QueryHandlerContext({
     required List<FoundElement> foundElements,
     required this.root,
@@ -32,6 +34,7 @@ class _QueryHandlerContext {
     required this.nestedScope,
     this.requestedResultClass,
     this.requestedResultType,
+    this.sourceForFixedName,
   }) : foundElements = List.unmodifiable(foundElements);
 }
 
@@ -72,7 +75,18 @@ class QueryAnalyzer {
     return referencesByName[name.toLowerCase()] as E;
   }
 
-  SqlQuery analyze(DriftQueryDeclaration declaration) {
+  /// Analyzes the query from its [declaration].
+  ///
+  /// This runs drfit-specific query analysis and lints on the query. It will
+  /// also detect read or written tables and a suitable result set for this
+  /// query in Dart.
+  ///
+  /// The [sourceForCustomName] can be set to the syntactic source responsible
+  /// for a [DefinedSqlQuery.existingDartType] or[DefinedSqlQuery.resultClassName],
+  /// respectively. It will improve the highlighted source span in error
+  /// messages.
+  SqlQuery analyze(DriftQueryDeclaration declaration,
+      {DriftTableName? sourceForCustomName}) {
     final nestedAnalyzer = NestedQueryAnalyzer();
     NestedQueriesContainer? nestedScope;
 
@@ -102,6 +116,7 @@ class QueryAnalyzer {
       requestedResultType: requestedResultType,
       root: context.root,
       nestedScope: nestedScope,
+      sourceForFixedName: sourceForCustomName,
     ));
 
     final linter = DriftSqlLinter(
@@ -349,7 +364,7 @@ class QueryAnalyzer {
         lints.add(AnalysisError(
           type: AnalysisErrorType.other,
           message: message,
-          relevantNode: queryContext.root,
+          relevantNode: queryContext.sourceForFixedName ?? queryContext.root,
         ));
       });
 

drift_dev/lib/src/analysis/resolver/shared/dart_types.dart

@@ -424,7 +424,7 @@ bool checkType(
   if (typeConverter != null) {
     expectedDartType = typeConverter.dartType;
     if (typeConverter.canBeSkippedForNulls && columnIsNullable) {
-      typeToCheck = typeSystem.promoteToNonNull(typeToCheck);
+      expectedDartType = typeProvider.makeNullable(expectedDartType);
     }
   } else {
     expectedDartType = typeProvider.typeFor(columnType, knownTypes);
@@ -503,7 +503,7 @@ extension CreateRecordType on TypeProvider {
     if (type is InterfaceType) {
       return type.element.instantiate(
         typeArguments: type.typeArguments,
-        nullabilitySuffix: NullabilitySuffix.none,
+        nullabilitySuffix: NullabilitySuffix.question,
       );
     } else if (type is NeverType) {
       return nullType;