fix(shorebird_cli): warn instead of error when no flavor provided to app that has flavors (#3352)

packages/shorebird_cli/lib/src/shorebird_validator.dart

@@ -175,6 +175,12 @@ To fix, update your pubspec.yaml to include the following:
 
       throw ValidationFailedException();
     }
+
+    if (validationIssuesContainsWarning(issues)) {
+      for (final issue in issues) {
+        logger.warn(issue.message);
+      }
+    }
   }
 
   /// Whether any [ValidationIssue]s have a severity of
@@ -182,6 +188,11 @@ To fix, update your pubspec.yaml to include the following:
   bool validationIssuesContainsError(List<ValidationIssue> issues) =>
       issues.any((issue) => issue.severity == ValidationIssueSeverity.error);
 
+  /// Whether any [ValidationIssue]s have a severity of
+  /// [ValidationIssueSeverity.warning].
+  bool validationIssuesContainsWarning(List<ValidationIssue> issues) =>
+      issues.any((issue) => issue.severity == ValidationIssueSeverity.warning);
+
   /// Logs a message indicating that validation failed. If any of the issues
   /// can be automatically fixed, this also prompts the user to run
   /// `shorebird doctor --fix`.

packages/shorebird_cli/lib/src/validators/flavor_validator.dart

@@ -23,7 +23,8 @@ class FlavorValidator extends Validator {
 
   @override
   Future<List<ValidationIssue>> validate() async {
-    final projectFlavors = shorebirdEnv.getShorebirdYaml()!.flavors;
+    final shorebirdYaml = shorebirdEnv.getShorebirdYaml()!;
+    final projectFlavors = shorebirdYaml.flavors;
     if (projectFlavors == null && flavorArg != null) {
       return [
         ValidationIssue.error(
@@ -35,9 +36,11 @@ class FlavorValidator extends Validator {
 
     if (projectFlavors != null && flavorArg == null) {
       return [
-        ValidationIssue.error(
+        ValidationIssue.warning(
           message:
-              '''The project has flavors ${projectFlavors.keys}, but no --flavor argument was provided''',
+              '''
+The project has flavors ${projectFlavors.keys}, but no --flavor argument was provided.
+The default app id ${shorebirdYaml.appId} will be used.''',
         ),
       ];
     }

packages/shorebird_cli/test/src/shorebird_validator_test.dart

@@ -283,7 +283,7 @@ To fix, update your pubspec.yaml to include the following:
 
         group('when platform supports flavors', () {
           group('when no flavor is specified', () {
-            test('fails validation', () async {
+            test('logs warning and fails validation', () async {
               await expectLater(
                 runWithOverrides(
                   () => shorebirdValidator.validateFlavors(
@@ -291,8 +291,15 @@ To fix, update your pubspec.yaml to include the following:
                     releasePlatform: ReleasePlatform.android,
                   ),
                 ),
-                throwsA(isA<ValidationFailedException>()),
+                completes,
               );
+              verify(
+                () => logger.warn(
+                  '''
+The project has flavors (flavorA), but no --flavor argument was provided.
+The default app id test will be used.''',
+                ),
+              ).called(1);
             });
           });
 

packages/shorebird_cli/test/src/validators/flavor_validator_test.dart

@@ -119,14 +119,15 @@ void main() {
             validator = FlavorValidator(flavorArg: null);
           });
 
-          test('returns validation error', () async {
+          test('returns validation warning', () async {
             final issues = await runWithOverrides(validator.validate);
             expect(
               issues,
               equals([
-                ValidationIssue.error(
-                  message:
-                      '''The project has flavors (flavorA, flavorB), but no --flavor argument was provided''',
+                ValidationIssue.warning(
+                  message: '''
+The project has flavors (flavorA, flavorB), but no --flavor argument was provided.
+The default app id $appId will be used.''',
                 ),
               ]),
             );