[lldb] Add synthetic formatter for Swift.TaskGroup (#10143)

Add synthetic data formatter for `TaskGroup`. This formatter prints the group's tasks using the previously added formatter for `Task`.

(cherry-picked from commit 065c58e)

Author: kastiglione

lldb/source/Plugins/Language/Swift/SwiftFormatters.cpp

@@ -16,9 +16,11 @@
 #include "Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.h"
 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
 #include "Plugins/TypeSystem/Swift/SwiftDemangle.h"
+#include "Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.h"
 #include "lldb/DataFormatters/FormattersHelpers.h"
 #include "lldb/DataFormatters/StringPrinter.h"
 #include "lldb/Symbol/CompilerType.h"
+#include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/DataBufferHeap.h"
@@ -28,11 +30,13 @@
 #include "lldb/Utility/Timer.h"
 #include "lldb/ValueObject/ValueObject.h"
 #include "lldb/lldb-enumerations.h"
+#include "swift/ABI/Task.h"
 #include "swift/AST/Types.h"
 #include "swift/Demangling/Demangle.h"
 #include "swift/Demangling/ManglingMacros.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/FormatAdapters.h"
 #include "llvm/Support/raw_ostream.h"
 #include <optional>
@@ -950,6 +954,188 @@ class TaskSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
   ValueObjectSP m_child_tasks_sp;
   ValueObjectSP m_is_running_sp;
 };
+
+class TaskGroupSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  TaskGroupSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
+      : SyntheticChildrenFrontEnd(*valobj_sp.get()) {
+    bool is_64bit = false;
+    if (auto target_sp = m_backend.GetTargetSP())
+      is_64bit = target_sp->GetArchitecture().GetTriple().isArch64Bit();
+
+    std::optional<uint32_t> concurrency_version;
+    if (auto process_sp = m_backend.GetProcessSP())
+      concurrency_version =
+          SwiftLanguageRuntime::FindConcurrencyDebugVersion(*process_sp);
+
+    m_is_supported_target = is_64bit && concurrency_version.value_or(0) == 1;
+  }
+
+  llvm::Expected<uint32_t> CalculateNumChildren() override {
+    if (!m_is_supported_target)
+      return m_backend.GetNumChildren();
+
+    return m_task_addrs.size();
+  }
+
+  bool MightHaveChildren() override { return true; }
+
+  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override {
+    if (!m_is_supported_target)
+      return m_backend.GetChildAtIndex(idx);
+
+    if (!m_task_type || idx >= m_task_addrs.size())
+      return {};
+
+    if (auto valobj_sp = m_children[idx])
+      return valobj_sp;
+
+    addr_t task_addr = m_task_addrs[idx];
+    auto child_name = ("[" + Twine(idx) + "]").str();
+    auto task_sp = ValueObject::CreateValueObjectFromAddress(
+        child_name, task_addr, m_backend.GetExecutionContextRef(), m_task_type,
+        false);
+    if (auto synthetic_sp = task_sp->GetSyntheticValue())
+      task_sp = synthetic_sp;
+
+    m_children[idx] = task_sp;
+    return task_sp;
+  }
+
+  size_t GetIndexOfChildWithName(ConstString name) override {
+    if (!m_is_supported_target)
+      return m_backend.GetIndexOfChildWithName(name);
+
+    StringRef buf = name.GetStringRef();
+    size_t idx = UINT32_MAX;
+    if (buf.consume_front("[") && !buf.consumeInteger(10, idx) && buf == "]")
+      return idx;
+    return UINT32_MAX;
+  }
+
+  lldb::ChildCacheState Update() override {
+    if (!m_is_supported_target)
+      return ChildCacheState::eReuse;
+
+    m_task_addrs.clear();
+    m_children.clear();
+
+    if (!m_task_type)
+      if (auto target_sp = m_backend.GetTargetSP()) {
+        if (auto ts_or_err = target_sp->GetScratchTypeSystemForLanguage(
+                eLanguageTypeSwift)) {
+          if (auto *ts = llvm::dyn_cast_or_null<TypeSystemSwiftTypeRef>(
+                  ts_or_err->get()))
+            // TypeMangling for "Swift.UnsafeCurrentTask"
+            m_task_type = ts->GetTypeFromMangledTypename(ConstString("$sSctD"));
+        } else {
+          LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters | LLDBLog::Types),
+                         ts_or_err.takeError(),
+                         "could not get Swift type system for Task synthetic "
+                         "provider: {0}");
+          return ChildCacheState::eReuse;
+        }
+      }
+
+    if (!m_task_type)
+      return ChildCacheState::eReuse;
+
+    // Get the (opaque) pointer to the `TaskGroupBase`.
+    addr_t task_group_ptr = LLDB_INVALID_ADDRESS;
+    if (auto opaque_group_ptr_sp = m_backend.GetChildMemberWithName("_group"))
+      task_group_ptr =
+          opaque_group_ptr_sp->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
+
+    TaskGroupBase task_group{m_backend.GetProcessSP(), task_group_ptr};
+
+    // Get the TaskGroup's child tasks by getting all tasks in the range
+    // [FirstChild, LastChild].
+    //
+    // Child tasks are connected together using ChildFragment::NextChild.
+    Status status;
+    auto current_task = task_group.getFirstChild(status);
+    auto last_task = task_group.getLastChild(status);
+    while (current_task) {
+      m_task_addrs.push_back(current_task.addr);
+      if (current_task == last_task)
+        break;
+      current_task = current_task.getNextChild(status);
+    }
+
+    // Populate the child cache with null values.
+    m_children.resize(m_task_addrs.size());
+
+    if (status.Fail()) {
+      LLDB_LOG(GetLog(LLDBLog::DataFormatters | LLDBLog::Types),
+               "could not read TaskGroup's child task pointers: {0}",
+               status.AsCString());
+      return ChildCacheState::eReuse;
+    }
+
+    return ChildCacheState::eRefetch;
+  }
+
+private:
+  /// Lightweight Task pointer wrapper, for the purpose of traversing to the
+  /// Task's next sibling (via `ChildFragment::NextChild`).
+  struct Task {
+    ProcessSP process_sp;
+    addr_t addr;
+
+    operator bool() const { return addr && addr != LLDB_INVALID_ADDRESS; }
+
+    bool operator==(const Task &other) const { return addr == other.addr; }
+    bool operator!=(const Task &other) const { return !(*this == other); }
+
+    static constexpr offset_t AsyncTaskSize = sizeof(::swift::AsyncTask);
+    static constexpr offset_t ChildFragmentOffset = AsyncTaskSize;
+    static constexpr offset_t NextChildOffset = ChildFragmentOffset + 0x8;
+
+    Task getNextChild(Status &status) {
+      addr_t next_task = LLDB_INVALID_ADDRESS;
+      if (status.Success())
+        next_task =
+            process_sp->ReadPointerFromMemory(addr + NextChildOffset, status);
+      return {process_sp, next_task};
+    }
+  };
+
+  /// Lightweight wrapper around TaskGroup opaque pointers (`TaskGroupBase`),
+  /// for the purpose of traversing its child tasks.
+  struct TaskGroupBase {
+    ProcessSP process_sp;
+    addr_t addr;
+
+    // FirstChild offset for a TaskGroupBase instance.
+    static constexpr offset_t FirstChildOffset = 0x18;
+    static constexpr offset_t LastChildOffset = 0x20;
+
+    Task getFirstChild(Status &status) {
+      addr_t first_child = LLDB_INVALID_ADDRESS;
+      if (status.Success())
+        first_child =
+            process_sp->ReadPointerFromMemory(addr + FirstChildOffset, status);
+      return {process_sp, first_child};
+    }
+
+    Task getLastChild(Status &status) {
+      addr_t last_child = LLDB_INVALID_ADDRESS;
+      if (status.Success())
+        last_child =
+            process_sp->ReadPointerFromMemory(addr + LastChildOffset, status);
+      return {process_sp, last_child};
+    }
+  };
+
+private:
+  bool m_is_supported_target = false;
+  // Type for Swift.UnsafeCurrentTask.
+  CompilerType m_task_type;
+  // The TaskGroup's list of child task addresses.
+  std::vector<addr_t> m_task_addrs;
+  // Cache and storage of constructed child values.
+  std::vector<ValueObjectSP> m_children;
+};
 }
 }
 }
@@ -1016,6 +1202,14 @@ lldb_private::formatters::swift::TaskSyntheticFrontEndCreator(
   return new TaskSyntheticFrontEnd(valobj_sp);
 }
 
+SyntheticChildrenFrontEnd *
+lldb_private::formatters::swift::TaskGroupSyntheticFrontEndCreator(
+    CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
+  if (!valobj_sp)
+    return nullptr;
+  return new TaskGroupSyntheticFrontEnd(valobj_sp);
+}
+
 bool lldb_private::formatters::swift::ObjC_Selector_SummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
   LLDB_SCOPED_TIMER();

lldb/source/Plugins/Language/Swift/SwiftFormatters.h

@@ -119,6 +119,9 @@ SyntheticChildrenFrontEnd *EnumSyntheticFrontEndCreator(CXXSyntheticChildren *,
 
 SyntheticChildrenFrontEnd *TaskSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                                         lldb::ValueObjectSP);
+
+SyntheticChildrenFrontEnd *
+TaskGroupSyntheticFrontEndCreator(CXXSyntheticChildren *, lldb::ValueObjectSP);
 }
 }
 }

lldb/source/Plugins/Language/Swift/SwiftLanguage.cpp

@@ -416,6 +416,11 @@ static void LoadSwiftFormatters(lldb::TypeCategoryImplSP swift_category_sp) {
                   lldb_private::formatters::swift::TaskSyntheticFrontEndCreator,
                   "Swift.UnsafeCurrentTask synthetic children",
                   ConstString("Swift.UnsafeCurrentTask"), synth_flags);
+  AddCXXSynthetic(
+      swift_category_sp,
+      lldb_private::formatters::swift::TaskGroupSyntheticFrontEndCreator,
+      "Swift.TaskGroup synthetic children",
+      ConstString("^Swift\\.TaskGroup<.+>"), synth_flags, true);
 
   AddCXXSummary(
       swift_category_sp, lldb_private::formatters::swift::Bool_SummaryProvider,

lldb/test/API/lang/swift/async/taskgroups/Makefile

@@ -0,0 +1,3 @@
+SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS := -parse-as-library
+include Makefile.rules

lldb/test/API/lang/swift/async/taskgroups/TestSwiftTaskGroupSynthetic.py

@@ -0,0 +1,43 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+
+    @swiftTest
+    def test_value_printing(self):
+        """Print a TaskGroup and verify its children."""
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.swift")
+        )
+        self.expect(
+            "v group",
+            substrs=[
+                "[0] = {",
+                "isGroupChildTask = true",
+                "[1] = {",
+                "isGroupChildTask = true",
+                "[2] = {",
+                "isGroupChildTask = true",
+            ],
+        )
+
+    @swiftTest
+    def test_value_api(self):
+        """Verify a TaskGroup contains its expected children."""
+        self.build()
+        _, process, _, _ = lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.swift")
+        )
+        thread = process.GetSelectedThread()
+        frame = thread.GetSelectedFrame()
+        group = frame.FindVariable("group")
+        self.assertEqual(group.num_children, 3)
+        for task in group:
+            self.assertEqual(str(task), str(group.GetChildMemberWithName(task.name)))
+            self.assertEqual(
+                task.GetChildMemberWithName("isGroupChildTask").summary, "true"
+            )

lldb/test/API/lang/swift/async/taskgroups/main.swift

@@ -0,0 +1,14 @@
+@main struct Main {
+    static func main() async {
+        await withTaskGroup { group in
+            for _ in 0..<3 {
+                group.addTask {
+                    try? await Task.sleep(for: .seconds(300))
+                }
+            }
+
+            print("break here")
+            for await _ in group {}
+        }
+    }
+}