[Lldb-commits] [lldb] [lldb-vscode] Display a more descriptive summary for containers and pointers (PR #65514)

[David Blaikie via lldb-commits]

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@@ -132,6 +132,84 @@ std::vector<std::string> GetStrings(const llvm::json::Object *obj,
   return strs;
 }
 
+/// Create a short summary for a container that contains the summary of its
+/// first children, so that the user can get a glimpse of its contents at a
+/// glance.
+static std::optional<std::string>
+GetSyntheticSummaryForContainer(lldb::SBValue &v) {
+  if (v.TypeIsPointerType() || !v.MightHaveChildren())
+    return std::nullopt;
+  /// As this operation can be potentially slow, we limit the total time spent
+  /// fetching children to a few ms.
+  const auto max_evaluation_time = std::chrono::milliseconds(10);
+  /// We don't want to generate a extremely long summary string, so we limit its
+  /// length.
+  const size_t max_length = 32;
+
+  auto start = std::chrono::steady_clock::now();
+  std::string summary;
+  llvm::raw_string_ostream os(summary);
+  os << "{";
+
+  llvm::StringRef separator = "";
+
+  for (size_t i = 0, e = v.GetNumChildren(); i < e; ++i) {
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dwblaikie wrote:

What do other debuggers do? (like Visual Studio itself)

& not sure that `GetNumChildren` should cause indefinite recursive expansion - could limit this feature to just going one level deep, for instance. But certainly worth comparing to other debuggers to see what sort of heuristics/rules/guidelines are good in terms of the amount of data expanded by default V unexpanded.

(& yeah, if everything's expanded all the way down, that's probably not good)

https://github.com/llvm/llvm-project/pull/65514