From f8f5d256df3199d610db7a379abde8debd04b19e Mon Sep 17 00:00:00 2001
From: Nate Bosch <nbosch@google.com>
Date: Tue, 17 Jun 2025 21:47:23 +0000
Subject: [PATCH] Keep generated file comments on the first line

Let linquist continue to find the generated file marker on the first
line, the dart format width comment is allowed to be on any line.

Look for the generated file line exactly and when it starts the file
insert the dart format comment following it.
---
 source_gen/CHANGELOG.md                            |  4 ++++
 source_gen/lib/src/builder.dart                    |  8 +++++++-
 source_gen/pubspec.yaml                            |  2 +-
 source_gen/test/builder_test.dart                  | 10 +++++-----
 source_gen/test/generator_for_annotation_test.dart |  6 +++---
 5 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/source_gen/CHANGELOG.md b/source_gen/CHANGELOG.md
index f299d63a..ff2875ec 100644
--- a/source_gen/CHANGELOG.md
+++ b/source_gen/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.0.1-WIP
+
+- Keep `// GENERATED FILE` comments on the first line.
+
 ## 2.0.0
 
 - **Breaking Change**: Change `formatOutput` function to accept a language
diff --git a/source_gen/lib/src/builder.dart b/source_gen/lib/src/builder.dart
index 53b8c2f7..c17d87d7 100644
--- a/source_gen/lib/src/builder.dart
+++ b/source_gen/lib/src/builder.dart
@@ -414,7 +414,13 @@ String _defaultFormatOutput(String code, Version version) =>
 
 /// Prefixes a dart format width and formats [code].
 String _defaultFormatUnit(String code, Version version) {
-  code = '$dartFormatWidth\n$code';
+  if (code.startsWith('$defaultFileHeader\n')) {
+    code = '$defaultFileHeader\n'
+        '$dartFormatWidth\n'
+        '${code.substring(defaultFileHeader.length)}';
+  } else {
+    code = '$dartFormatWidth\n$code';
+  }
   return _defaultFormatOutput(code, version);
 }
 
diff --git a/source_gen/pubspec.yaml b/source_gen/pubspec.yaml
index d650bb5c..3554ba73 100644
--- a/source_gen/pubspec.yaml
+++ b/source_gen/pubspec.yaml
@@ -1,5 +1,5 @@
 name: source_gen
-version: 2.0.0
+version: 2.0.1-WIP
 description: >-
   Source code generation builders and utilities for the Dart build system
 repository: https://github.com/dart-lang/source_gen/tree/master/source_gen
diff --git a/source_gen/test/builder_test.dart b/source_gen/test/builder_test.dart
index 87261476..791bbcb7 100644
--- a/source_gen/test/builder_test.dart
+++ b/source_gen/test/builder_test.dart
@@ -1067,8 +1067,8 @@ final int foo = 42
 ''';
 
 const _testGenPartContent = '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 part of 'test_lib.dart';
 
@@ -1081,8 +1081,8 @@ part of 'test_lib.dart';
 ''';
 
 const _testGenPartContentForLibrary = '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 part of 'test_lib.dart';
 
@@ -1094,8 +1094,8 @@ part of 'test_lib.dart';
 ''';
 
 const _testGenStandaloneContent = '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // CommentGenerator
@@ -1106,8 +1106,8 @@ $dartFormatWidth
 ''';
 
 const _testGenPartContentForClassesAndLibrary = '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 part of 'test_lib.dart';
 
@@ -1121,8 +1121,8 @@ part of 'test_lib.dart';
 ''';
 
 const _testGenNoLibrary = '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 part of 'test_lib.dart';
 
diff --git a/source_gen/test/generator_for_annotation_test.dart b/source_gen/test/generator_for_annotation_test.dart
index e78f6ad4..1ba7512d 100644
--- a/source_gen/test/generator_for_annotation_test.dart
+++ b/source_gen/test/generator_for_annotation_test.dart
@@ -44,8 +44,8 @@ void main() {
       _inputMap,
       outputs: {
         'a|lib/file.g.dart': '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // Generator: Repeating
@@ -129,8 +129,8 @@ $dartFormatWidth
       },
       outputs: {
         'a|lib/file.g.dart': '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // Generator: Deprecated
@@ -166,8 +166,8 @@ $dartFormatWidth
       },
       outputs: {
         'a|lib/file.g.dart': '''
-$dartFormatWidth
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // Generator: Deprecated