test(create): fail when template bundle vars drift from the CLI

lib/src/commands/create/commands/flutter_plugin.dart

@@ -41,5 +41,6 @@ class CreateFlutterPlugin({
   TemplateVarResolvers get templateVarResolvers => {
     ...super.templateVarResolvers,
     'platforms': () => argResults['platforms'] as List<String>,
+    'dart_fix_output': () => true,
   };
 }

lib/src/commands/create/templates/template.dart

@@ -19,6 +19,12 @@ abstract class const Template({
   /// {@macro template}
   this;
 
+  /// The [bundle] vars intentionally left to the template's default value.
+  ///
+  /// Every bundle var must either be passed by the `very_good create`
+  /// subcommand that uses this template or be listed here.
+  Set<String> get defaultedVars => const {};
+
   /// Callback invoked after template generation has completed.
   Future<void> onGenerateComplete(Logger logger, Directory outputDir);
 }

lib/src/commands/create/templates/very_good_flame_game/very_good_flame_game_template.dart

@@ -16,6 +16,11 @@ class VeryGoodFlameGameTemplate() extends Template {
         help: 'Generate a Very Good Flame game.',
       );
 
+  /// `application_id` is derived from `org_name` and `project_name` by the
+  /// template when omitted.
+  @override
+  Set<String> get defaultedVars => const {'application_id'};
+
   @override
   Future<void> onGenerateComplete(Logger logger, Directory outputDir) async {
     if (await installFlutterPackages(logger, outputDir)) {

test/src/commands/create/commands/flutter_plugin_test.dart

@@ -219,6 +219,7 @@ void main() {
               'publishable': false,
               'workspace': false,
               'platforms': ['android', 'ios', 'windows'],
+              'dart_fix_output': true,
             },
             onVarsChanged: any(named: 'onVarsChanged'),
           ),
@@ -233,6 +234,7 @@ void main() {
               'publishable': false,
               'workspace': false,
               'platforms': ['android', 'ios', 'windows'],
+              'dart_fix_output': true,
             },
             logger: logger,
           ),

test/src/commands/create/template_vars_test.dart

@@ -0,0 +1,68 @@
+import 'package:mason/mason.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:test/test.dart';
+import 'package:very_good_cli/src/commands/create/commands/commands.dart';
+import 'package:very_good_cli/src/commands/create/create.dart';
+
+class _MockLogger extends Mock implements Logger;
+
+void main() {
+  group('template vars', () {
+    final subcommands = CreateCommand(logger: _MockLogger()).subcommands.values
+        .toSet()
+        .cast<CreateSubCommand>();
+
+    for (final subcommand in subcommands) {
+      final templates = switch (subcommand) {
+        MultiTemplates(:final templates) => templates,
+        _ => [subcommand.template],
+      };
+
+      for (final template in templates) {
+        final bundle = template.bundle;
+        final bundleVars = bundle.vars.keys.toSet();
+        final handledVars = subcommand.templateVarResolvers.keys.toSet();
+        final defaultedVars = template.defaultedVars;
+        final source =
+            'very_good create ${subcommand.name} '
+            '(template "${template.name}", bundle "${bundle.name}")';
+
+        group('${subcommand.name} ${template.name}', () {
+          test('handles every bundle var', () {
+            expect(
+              bundleVars.difference(handledVars).difference(defaultedVars),
+              isEmpty,
+              reason:
+                  '$source does not pass these bundle vars. Add them to '
+                  "${subcommand.runtimeType}'s templateVarResolvers, or to "
+                  "${template.runtimeType}'s defaultedVars to keep the "
+                  'template default.',
+            );
+          });
+
+          test('only passes vars declared by the bundle', () {
+            expect(
+              handledVars.difference(bundleVars),
+              isEmpty,
+              reason:
+                  '$source passes these vars, but the bundle does not '
+                  'declare them. Remove them from '
+                  "${subcommand.runtimeType}'s templateVarResolvers.",
+            );
+          });
+
+          test('only defaults vars declared by the bundle', () {
+            expect(
+              defaultedVars.difference(bundleVars),
+              isEmpty,
+              reason:
+                  '$source defaults these vars, but the bundle does not '
+                  'declare them. Remove them from '
+                  "${template.runtimeType}'s defaultedVars.",
+            );
+          });
+        });
+      }
+    }
+  });
+}