[lldb][progress] Mitigate non-specific LLDB progress reports in Swift (#8664)

* [lldb][progress] Mitigate non-specific LLDB progress reports in Swift

When LLDB reports progress on importing Swift modules, it was delivering
non-specific progress reports with only the title of "Importing Swift
modules" and no details. To report progress on activity within Swift,
LLDB first creates a progress report then updates that progress report
using a callback that LLDB sets and the Swift compiler invokes when
performing a full import.

When LLDB triggers Swift to import modules that were already imported before,
Swift will not perform a full import. Since the progress report would've
already been displayed, but the callback is never invoked, this leads
to the non-specific messages that were being displayed when importing
Swift modules.

This commit sets a unique pointer to create a progress report from
within the callback function instead of creating the report before
setting the callback. It also clears the callback on scope exit instead
of setting it to a new progress report.

(cherry picked from commit 84e7e51)

* Update test for Swift progress reports

Updates the test for Swift progress reporting by checking that the
"Importing Swift modules" message only appears twice on its own as the
rest of the reports for this category will have details attached.

(cherry picked from commit 21e9d75)

Author: chelcassanova

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -2160,9 +2160,7 @@ SwiftASTContext::CreateInstance(lldb::LanguageType language, Module &module,
     auto on_exit = llvm::make_scope_exit([&]() {
       swift_ast_sp->m_ast_context_ap->SetPreModuleImportCallback(
           [](llvm::StringRef module_name,
-             swift::ASTContext::ModuleImportKind kind) {
-            Progress("Importing Swift modules");
-          });
+             swift::ASTContext::ModuleImportKind kind) {});
     });
 
     swift::ModuleDecl *stdlib =
@@ -2716,9 +2714,7 @@ lldb::TypeSystemSP SwiftASTContext::CreateInstance(
     auto on_exit = llvm::make_scope_exit([&]() {
       swift_ast_sp->m_ast_context_ap->SetPreModuleImportCallback(
           [](llvm::StringRef module_name,
-             swift::ASTContext::ModuleImportKind kind) {
-            Progress("Importing Swift modules");
-          });
+             swift::ASTContext::ModuleImportKind kind) {});
     });
 
     swift::ModuleDecl *stdlib =
@@ -3825,20 +3821,22 @@ swift::ModuleDecl *SwiftASTContext::GetModule(const SourceModule &module,
 
   // Report progress on module importing by using a callback function in
   // swift::ASTContext.
-  Progress progress("Importing Swift modules");
+  std::unique_ptr<Progress> progress;
   ast->SetPreModuleImportCallback(
       [&progress](llvm::StringRef module_name,
                   swift::ASTContext::ModuleImportKind kind) {
+        if (!progress)
+          progress = std::make_unique<Progress>("Importing Swift modules");
         switch (kind) {
         case swift::ASTContext::Module:
-          progress.Increment(1, module_name.str());
+          progress->Increment(1, module_name.str());
           break;
         case swift::ASTContext::Overlay:
-          progress.Increment(1, module_name.str() + " (overlay)");
+          progress->Increment(1, module_name.str() + " (overlay)");
           break;
         case swift::ASTContext::BridgingHeader:
-          progress.Increment(1,
-                             "Compiling bridging header: " + module_name.str());
+          progress->Increment(1, "Compiling bridging header: " +
+                                     module_name.str());
           break;
         }
       });
@@ -3848,9 +3846,7 @@ swift::ModuleDecl *SwiftASTContext::GetModule(const SourceModule &module,
   auto on_exit = llvm::make_scope_exit([&]() {
     ast->SetPreModuleImportCallback(
         [](llvm::StringRef module_name,
-           swift::ASTContext::ModuleImportKind kind) {
-          Progress("Importing Swift modules");
-        });
+           swift::ASTContext::ModuleImportKind kind) {});
   });
 
   // Perform the import.

lldb/test/API/functionalities/progress_reporting/swift_progress_reporting/TestSwiftProgressReporting.py

@@ -45,12 +45,22 @@ def test_swift_progress_report(self):
             "Importing Swift standard library",
         ]
 
+        importing_swift_reports = []
         while len(beacons):
             event = lldbutil.fetch_next_event(self, self.listener, self.broadcaster)
             ret_args = lldb.SBDebugger.GetProgressFromEvent(event)
             if self.TraceOn():
                 print(ret_args[0])
 
+            # When importing Swift modules, make sure that we don't get two reports
+            # in a row with the title "Importing Swift modules", i.e. there should be
+            # a report with that title followed by a report with that title and details
+            # attached.
+            if ret_args[0] == "Importing Swift modules":
+                next_event = lldbutil.fetch_next_event(self, self.listener, self.broadcaster)
+                next_ret_args = lldb.SBDebugger.GetProgressFromEvent(next_event)
+                self.assertRegexpMatches(next_ret_args[0], r"Importing Swift modules:+")
+
             for beacon in beacons:
                 if beacon in ret_args[0]:
                     beacons.remove(beacon)