Pass a Dart language version to the Dart formatter.

This will be required in an upcoming version of the Dart formatter.

PiperOrigin-RevId: 673452282

Author: srawlins

CHANGELOG.md

@@ -6,6 +6,8 @@
 * Require Dart >= 3.3.0.
 * Require analyzer 6.4.1.
 * Add support for extension types.
+* Require dart_style >= 2.3.7, so that the current Dart language version can be
+  passed to `DartFormatter`.
 
 ## 5.4.4
 

lib/src/builder.dart

@@ -144,7 +144,9 @@ class MockBuilder implements Builder {
     // The source lib may be pre-null-safety because of an explicit opt-out
     // (`// @dart=2.9`), as opposed to living in a pre-null-safety package. To
     // allow for this situation, we must also add an opt-out comment here.
-    final mockLibraryContent = DartFormatter().format('''
+    final mockLibraryContent =
+        DartFormatter(languageVersion: DartFormatter.latestLanguageVersion)
+            .format('''
 // Mocks generated by Mockito $packageVersion from annotations
 // in ${entryLib.definingCompilationUnit.source.uri.path}.
 // Do not manually edit this file.

pubspec.yaml

@@ -13,7 +13,7 @@ dependencies:
   build: ^2.0.0
   code_builder: ^4.5.0
   collection: ^1.15.0
-  dart_style: ^2.0.0
+  dart_style: ^2.3.7
   matcher: ^0.12.15
   meta: ^1.3.0
   path: ^1.8.0