[vm/debugger] Ensure TopLevel class is finalized when setting breakpoint

Following the revert #98360, make sure the finalizing happens only in debugger.
Create the test cases to demonstrate the behavior.

Bug: #35859
Change-Id: Ib27fef18a7c0696ec6dc6d045fa06f60677333c8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/98422
Reviewed-by: Alexander Markov <[email protected]>
Commit-Queue: Zichang Guo <[email protected]>

Author: zichangg

runtime/observatory/tests/service/breakpoint_partfile_test.dart

@@ -0,0 +1,37 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library breakpoint_in_parts_class;
+
+import 'package:observatory_test_package/has_part.dart' as hasPart;
+import 'test_helper.dart';
+import 'service_test_common.dart';
+
+const int LINE = 8;
+const String breakpointFile =
+    "package:observatory_test_package/the_part_2.dart";
+const String shortFile = "the_part_2.dart";
+
+code() {
+  hasPart.bar();
+}
+
+List<String> stops = [];
+
+List<String> expected = [
+  "$shortFile:${LINE + 0}:3", // on 'print'
+  "$shortFile:${LINE + 1}:1" // on class ending '}'
+];
+
+var tests = <IsolateTest>[
+  hasPausedAtStart,
+  setBreakpointAtUriAndLine(breakpointFile, LINE),
+  runStepThroughProgramRecordingStops(stops),
+  checkRecordedStops(stops, expected)
+];
+
+main(args) {
+  runIsolateTestsSynchronous(args, tests,
+      testeeConcurrent: code, pause_on_start: true, pause_on_exit: true);
+}

runtime/observatory/tests/service/observatory_test_package/has_part.dart

@@ -5,6 +5,7 @@
 library has_part;
 
 part 'the_part.dart';
+part 'the_part_2.dart';
 
 main() {
   Foo10 foo = new Foo10("Foo!");

runtime/observatory/tests/service/observatory_test_package/the_part_2.dart

@@ -0,0 +1,9 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of has_part;
+
+void bar() {
+  print('Should break here');
+}

runtime/vm/debugger.cc

@@ -3014,6 +3014,10 @@ BreakpointLocation* Debugger::BreakpointLocationAtLineCol(
   bool is_package = script_url.StartsWith(Symbols::PackageScheme());
   for (intptr_t i = 0; i < libs.Length(); i++) {
     lib ^= libs.At(i);
+    // Ensure that all top-level members are loaded so their scripts
+    // are available for look up. When certain script only contains
+    // top level functions, scripts could still be loaded correctly.
+    lib.EnsureTopLevelClassIsFinalized();
     script = lib.LookupScript(script_url, !is_package);
     if (!script.IsNull()) {
       scripts.Add(script);