Limit textual representation of arrays in debugger

runtime/bin/dbg_message.cc

Index: runtime/bin/dbg_message.cc
===================================================================
--- runtime/bin/dbg_message.cc	(revision 17421)
+++ runtime/bin/dbg_message.cc	(working copy)
@@ -105,7 +105,7 @@
 }
 
 
-static void FormatEncodedString(dart::TextBuffer* buf, Dart_Handle str) {
+static void FormatEncodedChars(dart::TextBuffer* buf, Dart_Handle str) {
   intptr_t str_len = 0;
   Dart_Handle res = Dart_StringLength(str, &str_len);
   ASSERT_NOT_ERROR(res);
@@ -116,51 +116,83 @@
   res = Dart_StringToUTF16(str, codepoints, &actual_len);
   ASSERT_NOT_ERROR(res);
   ASSERT(str_len == actual_len);
-  buf->AddChar('\"');
   for (int i = 0; i < str_len; i++) {
     buf->AddEscapedChar(codepoints[i]);
   }
-  buf->AddChar('\"');
   free(codepoints);
 }
 
 
-static void FormatErrorMsg(dart::TextBuffer* buf, Dart_Handle err) {
-  ASSERT(Dart_IsError(err));
-  const char* msg = Dart_GetError(err);
-  Dart_Handle str = Dart_NewStringFromCString(msg);
-  FormatEncodedString(buf, str);
+static void FormatEncodedString(dart::TextBuffer* buf, Dart_Handle str) {
+  buf->AddChar('\"');
+  FormatEncodedChars(buf, str);
+  buf->AddChar('\"');
 }
 
 
-static void FormatTextualValue(dart::TextBuffer* buf, Dart_Handle object) {
-  Dart_Handle text;
-  if (Dart_IsNull(object)) {
-    text = Dart_Null();
+static void FormatTextualListElement(dart::TextBuffer* buf,
+                                     Dart_Handle object) {
+  if (Dart_IsList(object)) {
+    buf->Printf("[...]");
+  } else if (Dart_IsNull(object)) {
+    buf->Printf("null");
+  } else if (Dart_IsError(object)) {
+    buf->Printf("#ERROR");
   } else {
-    Dart_ExceptionPauseInfo savedState = Dart_GetExceptionPauseInfo();
-
-    // TODO(hausner): Check whether recursive/reentrant pauses on exceptions
-    // should be prevented in Debugger::SignalExceptionThrown() instead.
-    if (savedState != kNoPauseOnExceptions) {
-      Dart_Handle res = Dart_SetExceptionPauseInfo(kNoPauseOnExceptions);
-      ASSERT_NOT_ERROR(res);
+    const bool need_quotes = Dart_IsString(object);
+    Dart_Handle text = Dart_ToString(object);
+    if (need_quotes) buf->Printf("\\\"");
+    if (Dart_IsNull(text)) {
+      buf->Printf("null");
+    } else if (Dart_IsError(text)) {
+      buf->Printf("#ERROR");
+    } else {
+      FormatEncodedChars(buf, text);
     }
+    if (need_quotes) buf->Printf("\\\"");
+  }
+}
 
-    text = Dart_ToString(object);
 
-    if (savedState != kNoPauseOnExceptions) {
-      Dart_Handle res = Dart_SetExceptionPauseInfo(savedState);
-      ASSERT_NOT_ERROR(res);
+static void FormatTextualListValue(dart::TextBuffer* buf, Dart_Handle list) {

[srdjan, 2013/01/23 18:35:45]

Do you want to do the same for very long Strings and Maps as well?

+  intptr_t len = 0;
+  Dart_Handle res = Dart_ListLength(list, &len);
+  ASSERT_NOT_ERROR(res);
+  const intptr_t initial_buffer_length = buf->length();
+  // Maximum number of characters we print for array elements.
+  const intptr_t max_chars = 256;
+  const intptr_t max_buffer_length = initial_buffer_length + max_chars;
+  buf->Printf("[");
+  for (int i = 0; i < len; i++) {
+    if (i > 0) {
+      buf->Printf(", ");
     }
+    Dart_Handle elem = Dart_ListGetAt(list, i);

[srdjan, 2013/01/23 18:35:45]

Instead of adding and checking if buffer exceeded, you could compute the length
first and then add the element on condition that it does not exceed the max
length, otherwise you still could end up with a huge buffer.

+    FormatTextualListElement(buf, elem);
+    if (buf->length() > max_buffer_length) {
+      buf->Printf(", ...");
+      break;
+    }
   }
-  buf->Printf("\"text\":");
-  if (Dart_IsNull(text)) {
+  buf->Printf("]");
+}
+
+
+static void FormatTextualValue(dart::TextBuffer* buf,
+                               Dart_Handle object) {
+  if (Dart_IsList(object)) {
+    FormatTextualListValue(buf, object);
+  } else if (Dart_IsNull(object)) {
     buf->Printf("null");
-  } else if (Dart_IsError(text)) {
-    FormatErrorMsg(buf, text);
   } else {
-    FormatEncodedString(buf, text);
+    Dart_Handle text = Dart_ToString(object);
+    if (Dart_IsNull(text)) {
+      buf->Printf("null");
+    } else if (Dart_IsError(text)) {
+      buf->Printf("#ERROR");
+    } else {
+      FormatEncodedChars(buf, text);
+    }
   }
 }
 
@@ -180,7 +212,9 @@
   } else {
     buf->Printf("\"kind\":\"object\",");
   }
+  buf->Printf("\"text\":\"");
   FormatTextualValue(buf, object);
+  buf->Printf("\"");
 }