feat: automate version.g.dart generation via build_runner

Replace manual generate_version.dart script with a custom build_runner
builder that automatically generates lib/version.g.dart from pubspec.yaml
during the build process. This eliminates manual steps and ensures version
info stays in sync.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -129,7 +129,9 @@ flutter run              # Default device
 
 ### Code Generation
 
-After modifying any `@freezed`, `@JsonSerializable`, or `@riverpod` annotated code:
+Run build_runner after modifying:
+- `@freezed`, `@JsonSerializable`, or `@riverpod` annotated code
+- `pubspec.yaml` version (auto-generates `lib/version.g.dart`)
 
 ```bash
 dart run build_runner build --delete-conflicting-outputs
@@ -138,6 +140,11 @@ dart run build_runner build --delete-conflicting-outputs
 dart run build_runner watch --delete-conflicting-outputs
 ```
 
+**Generated files**:
+- `*.freezed.dart` - Freezed immutable classes
+- `*.g.dart` - JSON serialization, Riverpod providers
+- `lib/version.g.dart` - App version from pubspec.yaml
+
 ## Deployment
 
 ### Web (Docker)

build.yaml

@@ -0,0 +1,8 @@
+builders:
+  version_builder:
+    import: "tool/version_builder.dart"
+    builder_factories: ["versionBuilder"]
+    build_extensions: { r"$package$": ["lib/version.g.dart"] }
+    auto_apply: root_package
+    build_to: source
+    runs_before: ["freezed", "riverpod_generator", "json_serializable"]

lib/version.g.dart

@@ -1,5 +1,5 @@
 // GENERATED FILE - DO NOT EDIT
-// Generated by: dart run tool/generate_version.dart
+// Generated by build_runner from pubspec.yaml
 
 /// Application version information from pubspec.yaml
 class AppVersion {

pubspec.yaml

@@ -76,6 +76,7 @@ dev_dependencies:
   mocktail: ^1.0.4
 
   # Build tools
+  build: ^2.4.0
   yaml: ^3.1.0
 
 # For information on the generic Dart part of this file, see the

tool/generate_version.dart

@@ -1,50 +0,0 @@
-#!/usr/bin/env dart
-/// Generates lib/version.g.dart from pubspec.yaml
-///
-/// Run before building: `dart run tool/generate_version.dart`
-
-import 'dart:io';
-
-import 'package:yaml/yaml.dart';
-
-void main() {
-  final pubspecFile = File('pubspec.yaml');
-  if (!pubspecFile.existsSync()) {
-    stderr.writeln('Error: pubspec.yaml not found');
-    exit(1);
-  }
-
-  final pubspec = loadYaml(pubspecFile.readAsStringSync()) as YamlMap;
-
-  final name = pubspec['name'] as String;
-  final description = pubspec['description'] as String;
-  final versionString = pubspec['version'] as String;
-
-  // Parse version: "0.1.0+1" -> version="0.1.0", buildNumber=1
-  final versionParts = versionString.split('+');
-  final version = versionParts[0];
-  final buildNumber = versionParts.length > 1 ? int.parse(versionParts[1]) : 0;
-
-  final output = '''
-// GENERATED FILE - DO NOT EDIT
-// Generated by: dart run tool/generate_version.dart
-
-/// Application version information from pubspec.yaml
-class AppVersion {
-  AppVersion._();
-
-  static const String name = '$name';
-  static const String description = '$description';
-  static const String version = '$version';
-  static const int buildNumber = $buildNumber;
-  static const String fullVersion = '$version+$buildNumber';
-}
-''';
-
-  final outputFile = File('lib/version.g.dart');
-  outputFile.writeAsStringSync(output);
-
-  print('Generated lib/version.g.dart');
-  print('  name: $name');
-  print('  version: $version+$buildNumber');
-}

tool/version_builder.dart

@@ -0,0 +1,49 @@
+import 'dart:async';
+
+import 'package:build/build.dart';
+import 'package:yaml/yaml.dart';
+
+/// Builder that generates version.g.dart from pubspec.yaml.
+Builder versionBuilder(BuilderOptions options) => VersionBuilder();
+
+class VersionBuilder implements Builder {
+  @override
+  final buildExtensions = const {
+    r'$package$': ['lib/version.g.dart'],
+  };
+
+  @override
+  Future<void> build(BuildStep buildStep) async {
+    final pubspecId = AssetId(buildStep.inputId.package, 'pubspec.yaml');
+    final pubspecContent = await buildStep.readAsString(pubspecId);
+    final pubspec = loadYaml(pubspecContent) as YamlMap;
+
+    final name = pubspec['name'] as String;
+    final description = pubspec['description'] as String? ?? '';
+    final versionString = pubspec['version'] as String;
+
+    // Parse version: "0.2.0+2" -> version="0.2.0", buildNumber=2
+    final versionParts = versionString.split('+');
+    final version = versionParts[0];
+    final buildNumber = versionParts.length > 1 ? int.parse(versionParts[1]) : 0;
+
+    final output = '''
+// GENERATED FILE - DO NOT EDIT
+// Generated by build_runner from pubspec.yaml
+
+/// Application version information from pubspec.yaml
+class AppVersion {
+  AppVersion._();
+
+  static const String name = '$name';
+  static const String description = '$description';
+  static const String version = '$version';
+  static const int buildNumber = $buildNumber;
+  static const String fullVersion = '$version+$buildNumber';
+}
+''';
+
+    final outputId = AssetId(buildStep.inputId.package, 'lib/version.g.dart');
+    await buildStep.writeAsString(outputId, output);
+  }
+}