Implement rewind: drop one or more frames from the debugger.

runtime/observatory/tests/service/rewind_test.dart

Index: runtime/observatory/tests/service/rewind_test.dart
diff --git a/runtime/observatory/tests/service/rewind_test.dart b/runtime/observatory/tests/service/rewind_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..152d711d40d98fff3f38ce7b702ed05a0254ec73
--- /dev/null
+++ b/runtime/observatory/tests/service/rewind_test.dart
@@ -0,0 +1,173 @@
+// Copyright (c) 2016, 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.
+// VMOptions=--error_on_bad_type --error_on_bad_override
+
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+const alwaysInline = "AlwaysInline";
+const noInline = "NeverInline";
+
+int LINE_A = 35;
+int LINE_B = 40;
+int LINE_C = 43;
+int LINE_D = 47;
+
+int global = 0;
+
+@noInline
+b3(x) {
+  int sum = 0;
+  try {
+    for (int i = 0; i < x; i++) {
+      sum += x;
+    }
+  } catch (e) {
+    print("caught $e");
+  }
+  if (global >= 100) {
+    debugger();
+  }
+  global = global + 1;  // Line A
+  return sum;
+}
+
+@alwaysInline
+b2(x) => b3(x);  // Line B
+
+@alwaysInline
+b1(x) => b2(x);  // Line C
+
+test() {
+  while (true) {
+    b1(10000);  // Line D
+  }
+}
+
+var tests = [
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // We are not able to rewind frame 0.
+    bool caughtException;
+    try {
+      await isolate.rewind(0);
+      expect(false, isTrue, reason:'Unreachable');
+    } on ServerRpcException catch(e) {
+      caughtException = true;
+      expect(e.code, equals(ServerRpcException.kCannotResume));
+      expect(e.message, 'Frame must be in bounds [1..9]: saw 0');
+    }
+    expect(caughtException, isTrue);
+  },
+
+  (Isolate isolate) async {
+    // We are not able to rewind frame 10.
+    bool caughtException;
+    try {
+      await isolate.rewind(10);
+      expect(false, isTrue, reason:'Unreachable');
+    } on ServerRpcException catch(e) {
+      caughtException = true;
+      expect(e.code, equals(ServerRpcException.kCannotResume));
+      expect(e.message, 'Frame must be in bounds [1..9]: saw 10');
+    }
+    expect(caughtException, isTrue);
+  },
+
+  (Isolate isolate) async {
+    // We are at our breakpoint with global=100.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Rewind the top stack frame.
+    result = await isolate.rewind(1);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_B),
+
+  (Isolate isolate) async {
+    var result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // global still is equal to 100.  We did not execute "global++".
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Resume again, for fun.
+    result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // global is now 101.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('101'));
+
+    // Rewind up to 'test'/
+    result = await isolate.rewind(3);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_D),
+
+  (Isolate isolate) async {
+    // Reset global to 0 and start again.
+    var result = await isolate.rootLibrary.evaluate('global=0');
+    print('set global to $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('0'));
+
+    result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // We are at our breakpoint with global=100.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Rewind the top 2 stack frames.
+    result = await isolate.rewind(2);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_C),
+];
+
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: test,
+                              extraArgs:
+                              ['--trace-rewind',
+                               '--no-prune-dead-locals',
+                               '--enable-inlining-annotations',
+                               '--no-background-compilation',
+                               '--optimization-counter-threshold=10']);