Add version for intermediate sources if needed

drift_dev/lib/src/backends/build/analyzer.dart

@@ -1,6 +1,11 @@
 import 'dart:convert';
+import 'dart:isolate';
 
 import 'package:build/build.dart';
+import 'package:package_config/package_config.dart';
+import 'package:package_config/package_config_types.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:yaml/yaml.dart';
 
 import '../../analysis/driver/driver.dart';
 import '../../analysis/options.dart';
@@ -54,6 +59,14 @@ class DriftAnalyzer extends Builder {
       await buildStep.writeAsBytes(jsonOutput, asJson);
 
       if (serialized.dartTypes.isNotEmpty) {
+        // We're using general typedefs in the generated helper code, which rely
+        // on Dart 2.13. We could just add a // @2.13 comment at the top, but
+        // we also want to be able to use newer features if the source package
+        // opted in to them (e.g. to be able to express records in here).
+        // So, we need to know about the package version from the pubspec.
+        final version = await buildStep.languageVersionForPackage ??
+            _languageVersionForGeneralizedTypedefs;
+
         final imports = LibraryInputManager();
         final writer = Writer(
           options,
@@ -61,6 +74,11 @@ class DriftAnalyzer extends Builder {
         );
         imports.linkToWriter(writer);
 
+        // We prefer newer versions, but we really need 2.13
+        if (version.compareTo(_languageVersionForGeneralizedTypedefs) < 0) {
+          writer.leaf().write('// @dart=2.13');
+        }
+
         for (var i = 0; i < serialized.dartTypes.length; i++) {
           writer.leaf()
             ..write('typedef T$i = ')
@@ -72,4 +90,29 @@ class DriftAnalyzer extends Builder {
       }
     }
   }
+
+  static final _languageVersionForGeneralizedTypedefs = LanguageVersion(2, 13);
+}
+
+extension on BuildStep {
+  Future<LanguageVersion?> get languageVersionForPackage async {
+    try {
+      final configUri = await Isolate.packageConfig;
+      if (configUri == null) return null;
+
+      final packageConfig = await loadPackageConfigUri(configUri);
+
+      for (final package in packageConfig.packages) {
+        if (package.name == inputId.package) {
+          return package.languageVersion;
+        }
+      }
+    } on Object {
+      // Can't read version, so be it
+      log.fine('Could not resolve language version of package to determine '
+          'whether a //@dart comment is necessary for intermediate sources');
+    }
+
+    return null;
+  }
 }