Add StackTrace.current getter.

R=floitsch@google.com, iposva@google.com, sra@google.com

Review URL: https://codereview.chromium.org/1448003002.

CHANGELOG.md

@@ -5,6 +5,7 @@
   * `Base64Decoder.convert` now takes optional `start` and `end` parameters.
 
 * `dart:core`
+  * Added `current` getter to `StackTrace` class.
   * Added `Uri.data` getter for `data:` URIs, and `UriData` class for the
     return type.
   * Added `growable` parameter to `List.filled` constructor.

runtime/lib/core_patch.dart

@@ -73,3 +73,7 @@ class _SyncIterator implements Iterator {
     }
   }
 }
+
+patch class StackTrace {
+  /* patch */ static StackTrace get current native "StackTrace_current";
+}

runtime/lib/stacktrace.cc

@@ -11,7 +11,8 @@
 namespace dart {
 
 static void IterateFrames(const GrowableObjectArray& code_list,
-                          const GrowableObjectArray& pc_offset_list) {
+                          const GrowableObjectArray& pc_offset_list,
+                          int skip_frames) {
   StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
@@ -19,15 +20,35 @@ static void IterateFrames(const GrowableObjectArray& code_list,
   Smi& offset = Smi::Handle();
   while (frame != NULL) {
     if (frame->IsDartFrame()) {
-      code = frame->LookupDartCode();
-      offset = Smi::New(frame->pc() - code.EntryPoint());
-      code_list.Add(code);
-      pc_offset_list.Add(offset);
+      if (skip_frames > 0) {
+        skip_frames--;
+      } else {
+        code = frame->LookupDartCode();
+        offset = Smi::New(frame->pc() - code.EntryPoint());
+        code_list.Add(code);
+        pc_offset_list.Add(offset);
+      }
     }
     frame = frames.NextFrame();
   }
 }
 
+// Creates a Stacktrace object from the current stack.
+//
+// Skips the first skip_frames Dart frames.
+static const Stacktrace& GetCurrentStacktrace(int skip_frames) {
+  const GrowableObjectArray& code_list =
+      GrowableObjectArray::Handle(GrowableObjectArray::New());
+  const GrowableObjectArray& pc_offset_list =
+      GrowableObjectArray::Handle(GrowableObjectArray::New());
+  IterateFrames(code_list, pc_offset_list, skip_frames);
+  const Array& code_array = Array::Handle(Array::MakeArray(code_list));
+  const Array& pc_offset_array =
+      Array::Handle(Array::MakeArray(pc_offset_list));
+  const Stacktrace& stacktrace = Stacktrace::Handle(
+      Stacktrace::New(code_array, pc_offset_array));
+  return stacktrace;
+}
 
 // An utility method for convenient printing of dart stack traces when
 // inside 'gdb'. Note: This function will only work when there is a
@@ -35,17 +56,13 @@ static void IterateFrames(const GrowableObjectArray& code_list,
 // set in dart code and control is got inside 'gdb' without going through
 // the runtime or native transition stub.
 void _printCurrentStacktrace() {
-  const GrowableObjectArray& code_list =
-      GrowableObjectArray::Handle(GrowableObjectArray::New());
-  const GrowableObjectArray& pc_offset_list =
-      GrowableObjectArray::Handle(GrowableObjectArray::New());
-  IterateFrames(code_list, pc_offset_list);
-  const Array& code_array = Array::Handle(Array::MakeArray(code_list));
-  const Array& pc_offset_array =
-      Array::Handle(Array::MakeArray(pc_offset_list));
-  const Stacktrace& stacktrace = Stacktrace::Handle(
-      Stacktrace::New(code_array, pc_offset_array));
+  const Stacktrace& stacktrace = GetCurrentStacktrace(0);
   OS::PrintErr("=== Current Trace:\n%s===\n", stacktrace.ToCString());
 }
 
+DEFINE_NATIVE_ENTRY(StackTrace_current, 0) {
+  const Stacktrace& stacktrace = GetCurrentStacktrace(1);
+  return stacktrace.raw();
+}
+
 }  // namespace dart

runtime/vm/bootstrap_natives.h

@@ -151,6 +151,7 @@ namespace dart {
   V(DateNatives_localTimeZoneAdjustmentInSeconds, 0)                           \
   V(AssertionError_throwNew, 2)                                                \
   V(Async_rethrow, 2)                                                          \
+  V(StackTrace_current, 0)                                                     \
   V(TypeError_throwNew, 5)                                                     \
   V(FallThroughError_throwNew, 1)                                              \
   V(AbstractClassInstantiationError_throwNew, 2)                               \

sdk/lib/_internal/js_runtime/lib/core_patch.dart

@@ -5,21 +5,22 @@
 // Patch file for dart:core classes.
 import "dart:_internal" as _symbol_dev;
 import 'dart:_interceptors';
-import 'dart:_js_helper' show patch,
+import 'dart:_js_helper' show checkInt,
+                              Closure,
+                              ConstantMap,
+                              getRuntimeType,
+                              JsLinkedHashMap;
+                              jsonEncodeNative,
+                              JSSyntaxRegExp,
+                              NoInline,
+                              objectHashCode,
+                              patch,
                               patch_full,
                               patch_lazy,
                               patch_startup,
-                              checkInt,
-                              getRuntimeType,
-                              jsonEncodeNative,
-                              JSSyntaxRegExp,
                               Primitives,
-                              ConstantMap,
-                              stringJoinUnchecked,
-                              objectHashCode,
-                              Closure,
                               readHttp,
-                              JsLinkedHashMap;
+                              stringJoinUnchecked,
 
 import 'dart:_foreign_helper' show JS;
 
@@ -671,3 +672,24 @@ class _Resource implements Resource {
     });
   }
 }
+
+@patch
+class StackTrace {
+  @patch
+  @NoInline()
+  static StackTrace get current {
+    var error = JS('', 'new Error()');
+    var stack = JS('String|Null', '#.stack', error);
+    if (stack is String) return new StackTrace.fromString(stack);
+    if (JS('', 'Error.captureStackTrace') != null) {
+      JS('void', 'Error.captureStackTrace(#)', error);
+      var stack = JS('String|Null', '#.stack', error);
+      if (stack is String) return new StackTrace.fromString(stack);
+    }
+    try {
+      throw 0;
+    } catch (_, stackTrace) {
+      return stackTrace;
+    }
+  }
+}

sdk/lib/core/stacktrace.dart

@@ -30,6 +30,18 @@ abstract class StackTrace {
    */
   factory StackTrace.fromString(String stackTraceString) = _StringStackTrace;
 
+  /**
+   * Returns a representation of the current stack trace.
+   *
+   * This is similar to what can be achieved by doing:
+   *
+   *     try { throw 0; } catch (_, stack) { return stack; }
+   *
+   * The getter achieves this without throwing, except on platforms that
+   * have no other way to get a stack trace.
+   */
+  external static StackTrace get current;
+
   /**
    * Returns a [String] representation of the stack trace.
    *

tests/corelib/stacktrace_current_test.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2015, 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.
+
+import "dart:convert" show LineSplitter;
+
+import "package:expect/expect.dart";
+
+void main() {
+  var st0;
+  var st1;
+  // Primitive way to get stack trace,.
+  try { throw 0; } catch (_, s) { st0 = s; }
+  st1 = StackTrace.current;
+
+  var st0s = findMain(st0);
+  var st1s = findMain(st1);
+  // Stack traces are not equal (contains at least a different line number,
+  // and possible different frame numbers).
+  // They are *similar*, so check that they agree on everything but numbers.
+  var digits = new RegExp(r"\d+");
+  Expect.equals(st0s.replaceAll(digits, "0"), st1s.replaceAll(digits, "0"));
+}
+
+String findMain(StackTrace stack) {
+  var string = "$stack";
+  var lines = LineSplitter.split(string).toList();
+  while (lines.isNotEmpty && !lines.first.contains("main")) {
+    lines.removeAt(0);
+  }
+  return lines.join("\n");
+}

tests/language/stacktrace_test.dart

@@ -1,4 +1,3 @@
-
 // Copyright (c) 2013, 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.