fix: filter out error messages from killing the server process (#592)

Co-authored-by: Jochum van der Ploeg <jochum.vanderploeg@verygood.ventures>

Author: renancaraujo

packages/dart_frog_cli/lib/src/commands/dev/dev.dart

@@ -37,6 +37,9 @@ typedef RestorableDirectoryGeneratorTargetBuilder
 /// Typedef for [io.exit].
 typedef Exit = dynamic Function(int exitCode);
 
+/// Regex for detecting warnings in the output of `dart run`.
+final _warningRegex = RegExp(r'^.*:\d+:\d+: Warning: .*', multiLine: true);
+
 RestorableDirectoryGeneratorTarget _defaultGeneratorTarget(Logger? logger) {
   return RestorableDirectoryGeneratorTarget(
     io.Directory(
@@ -156,9 +159,16 @@ class DevCommand extends DartFrogCommand {
         final message = utf8.decode(_).trim();
         if (message.isEmpty) return;
 
-        logger.err(message);
+        /// Do not kill the process if the error is a warning from the SDK.
+        final isSDKWarning = _warningRegex.hasMatch(message);
+
+        if (isSDKWarning) {
+          logger.warn(message);
+        } else {
+          logger.err(message);
+        }
 
-        if (!hotReloadEnabled) {
+        if (!hotReloadEnabled && !isSDKWarning) {
           await _killProcess(process);
           logger.detail('[process] exit(1)');
           _exit(1);
@@ -260,6 +270,7 @@ class RestorableDirectoryGeneratorTarget extends DirectoryGeneratorTarget {
   final CreateFile? _createFile;
   final Logger? _logger;
   final Queue<CachedFile> _cachedSnapshots;
+
   CachedFile? get _cachedSnapshot {
     return _cachedSnapshots.isNotEmpty ? _cachedSnapshots.last : null;
   }

packages/dart_frog_cli/test/src/commands/dev/dev_test.dart

@@ -657,6 +657,73 @@ void main() {
       verifyNever(() => process.kill());
     });
 
+    test(
+      'dont kills process if a warning occurs before '
+      'hotreload is enabled',
+      () async {
+        const warningMessage = """
+lib/my_model.g.dart:53:20: Warning: Operand of null-aware operation '!' has type 'String' which excludes null.
+          ? _value.name!
+                   ^
+          """;
+        final generatorHooks = _MockGeneratorHooks();
+        when(
+          () => generatorHooks.preGen(
+            vars: any(named: 'vars'),
+            workingDirectory: any(named: 'workingDirectory'),
+            onVarsChanged: any(named: 'onVarsChanged'),
+          ),
+        ).thenAnswer((invocation) async {
+          (invocation.namedArguments[const Symbol('onVarsChanged')] as void
+                  Function(Map<String, dynamic> vars))
+              .call(<String, dynamic>{});
+        });
+        when(
+          () => generator.generate(
+            any(),
+            vars: any(named: 'vars'),
+            fileConflictResolution: FileConflictResolution.overwrite,
+          ),
+        ).thenAnswer((_) async => []);
+        when(() => generator.hooks).thenReturn(generatorHooks);
+        when(() => process.stdout).thenAnswer((_) => const Stream.empty());
+        when(() => process.stderr).thenAnswer(
+          (_) => Stream.value(
+            utf8.encode(warningMessage),
+          ),
+        );
+        when(
+          () => directoryWatcher.events,
+        ).thenAnswer(
+          (_) => Stream.value(WatchEvent(ChangeType.MODIFY, 'README.md')),
+        );
+        command = DevCommand(
+          logger: logger,
+          ensureRuntimeCompatibility: (_) {},
+          directoryWatcher: (_) => directoryWatcher,
+          generator: (_) async => generator,
+          startProcess: (
+            String executable,
+            List<String> arguments, {
+            bool runInShell = false,
+          }) async {
+            return process;
+          },
+          sigint: sigint,
+        )..testArgResults = argResults;
+        final exitCode = await command.run();
+        expect(exitCode, equals(ExitCode.success.code));
+        verify(
+          () => generatorHooks.preGen(
+            vars: <String, dynamic>{'port': '8080'},
+            workingDirectory: any(named: 'workingDirectory'),
+            onVarsChanged: any(named: 'onVarsChanged'),
+          ),
+        ).called(1);
+        verifyNever(() => process.kill());
+        verify(() => logger.warn(warningMessage.trim())).called(1);
+      },
+    );
     test(
         'kills process if error occurs before '
         'hotreload is enabled on non-windows', () async {