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

[Walter Erquinigo 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) {
+    // If we reached the time limit or exceeded the number of characters, we
+    // dump `...` to signal that there are more elements in the collection.
+    if (summary.size() > max_length ||
+        (std::chrono::steady_clock::now() - start) > max_evaluation_time) {
+      os << separator << "...";
+      break;
+    }
+    lldb::SBValue child = v.GetChildAtIndex(i);
+
+    if (llvm::StringRef name = child.GetName(); !name.empty()) {
+      llvm::StringRef value;
+      if (llvm::StringRef summary = child.GetSummary(); !summary.empty())
+        value = summary;
+      else
+        value = child.GetValue();
+
+      if (!value.empty()) {
+        // If the child is an indexed entry, we don't show its index to save
+        // characters.
+        if (name.starts_with("["))
+          os << separator << value;
+        else
+          os << separator << name << ":" << value;
+        separator = ", ";
+      }
+    }
+  }
+  os << "}";
+
+  if (summary == "{...}" || summary == "{}")
+    return std::nullopt;
+  return summary;
+}
+
+/// Return whether we should dereference an SBValue in order to generate a more
+/// meaningful summary string.
+static bool ShouldBeDereferencedForSummary(lldb::SBValue &v) {
+  if (!v.GetType().IsPointerType() && !v.GetType().IsReferenceType())
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walter-erquinigo wrote:

Yep, there's a test that includes a char**.

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