[lldb] Use one Progress event per root module build

Following the work done by @JDevlieghere in D143690, this changes how Clang module build
events are emitted.

Instead of one Progress event per module being built, a single Progress event is used to
encompass all modules, and each module build is sent as an `Increment` update.

Differential Revision: https://reviews.llvm.org/D147248

Author: kastiglione

lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp

@@ -68,7 +68,7 @@ class StoringDiagnosticConsumer : public clang::DiagnosticConsumer {
 
 private:
   bool HandleModuleRemark(const clang::Diagnostic &info);
-  void SetCurrentModuleProgress(llvm::StringRef module_name);
+  void SetCurrentModuleProgress(std::string module_name);
 
   typedef std::pair<clang::DiagnosticsEngine::Level, std::string>
       IDAndDiagnostic;
@@ -208,8 +208,9 @@ bool StoringDiagnosticConsumer::HandleModuleRemark(
     if (m_module_build_stack.empty()) {
       m_current_progress_up = nullptr;
     } else {
-      // Update the progress to re-show the module that was currently being
-      // built from the time the now completed module was originally began.
+      // When the just completed module began building, a module that depends on
+      // it ("module A") was effectively paused. Update the progress to re-show
+      // "module A" as continuing to be built.
       const auto &resumed_module_name = m_module_build_stack.back();
       SetCurrentModuleProgress(resumed_module_name);
     }
@@ -224,13 +225,12 @@ bool StoringDiagnosticConsumer::HandleModuleRemark(
 }
 
 void StoringDiagnosticConsumer::SetCurrentModuleProgress(
-    llvm::StringRef module_name) {
-  // Ensure the ordering of:
-  //   1. Completing the existing progress event.
-  //   2. Beginining a new progress event.
-  m_current_progress_up = nullptr;
-  m_current_progress_up = std::make_unique<Progress>(
-      llvm::formatv("Currently building module {0}", module_name));
+    std::string module_name) {
+  if (!m_current_progress_up)
+    m_current_progress_up =
+        std::make_unique<Progress>("Building Clang modules");
+
+  m_current_progress_up->Increment(1, std::move(module_name));
 }
 
 ClangModulesDeclVendor::ClangModulesDeclVendor()

lldb/test/API/functionalities/progress_reporting/clang_modules/TestClangModuleBuildProgress.py

@@ -43,4 +43,4 @@ def test_clang_module_build_progress_report(self):
         event = lldbutil.fetch_next_event(self, listener, broadcaster)
         payload = lldb.SBDebugger.GetProgressFromEvent(event)
         message = payload[0]
-        self.assertEqual(message, "Currently building module MyModule")
+        self.assertEqual(message, "Building Clang modules")