[dds/dap] Don't include empty output events when output ends with \n

Empty output events are harmless but unnecessary. The stack frame parsing code would always send one with the output ended with \n which until recently was only for stderr, but recently was enabled for stdout.

The extra events broke some Flutter tests that were not expecting them.

See flutter/flutter#147250 (comment)

Change-Id: I13624f763d57a089d6b2d2c9e794cafb6a2f0023
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/364340
Commit-Queue: Ben Konyi <bkonyi@google.com>
Commit-Queue: Helin Shiah <helinx@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
Reviewed-by: Helin Shiah <helinx@google.com>

pkg/dds/lib/src/dap/adapters/dart.dart

@@ -2265,6 +2265,13 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
       final lineEnd = i != lines.length - 1 ? '\n' : '';
       final output = '$linePrefix$line$lineSuffix$lineEnd';
 
+      // If the output is empty (for example the output ended with \n so after
+      // splitting by \n, the last iteration is empty) then we don't need
+      // to add any event.
+      if (output.isEmpty) {
+        continue;
+      }
+
       final clientPath =
           fileLikeUri != null ? toClientPathOrUri(fileLikeUri) : null;
       events.add(

pkg/dds/test/dap/integration/debug_test.dart

@@ -50,6 +50,27 @@ main() {
       ]);
     });
 
+    test('does not include empty output events when output ends with a newline',
+        () async {
+      final testFile = dap.createTestFile(simpleArgPrintingProgram);
+
+      final outputEvents = await dap.client.collectOutput(
+        launch: () => dap.client.launch(
+          testFile.path,
+          args: ['one', 'two'],
+        ),
+      );
+
+      // The sample application uses `print()` which includes newlines on
+      // each output. Output is split by `\n` when scanning for stack frames
+      // and previously would include empty output events at the end if the
+      // content ended with a newline.
+      // https://github.com/flutter/flutter/pull/147250#issuecomment-2075128834
+      for (var output in outputEvents) {
+        expect(output.output, isNotEmpty);
+      }
+    });
+
     test('runs a simple script using runInTerminal request', () async {
       final testFile = dap.createTestFile(emptyProgram);