From 0dd4655008848bf45cb6881f7d3a9649701470b1 Mon Sep 17 00:00:00 2001
From: Artem Chikin <achikin@apple.com>
Date: Mon, 8 Dec 2025 14:50:08 -0800
Subject: [PATCH] [Test][Dependency Scanning] Add a compiler statistic for # of
 dependency module queries and a simple test for it

This adds a compiler statistic for # of named lookups the scanner performed.
---
 .../ModuleDependencyScanner.cpp               |  9 +++++
 test/ScanDependencies/basic_query_stats.swift | 39 +++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 test/ScanDependencies/basic_query_stats.swift

diff --git a/lib/DependencyScan/ModuleDependencyScanner.cpp b/lib/DependencyScan/ModuleDependencyScanner.cpp
index 83c60ed7e0177..f4bee95963859 100644
--- a/lib/DependencyScan/ModuleDependencyScanner.cpp
+++ b/lib/DependencyScan/ModuleDependencyScanner.cpp
@@ -26,6 +26,7 @@
 #include "swift/Basic/Defer.h"
 #include "swift/Basic/FileTypes.h"
 #include "swift/Basic/PrettyStackTrace.h"
+#include "swift/Basic/Statistic.h"
 #include "swift/ClangImporter/ClangImporter.h"
 #include "swift/Frontend/CompileJobCacheKey.h"
 #include "swift/Frontend/ModuleInterfaceLoader.h"
@@ -53,6 +54,12 @@
 
 using namespace swift;
 
+#define DEBUG_TYPE "DependencyScanner"
+STATISTIC(DepScanSwiftModuleQueries,
+          "# of times the dependency scanner performed a named lookup of a Swift module");
+STATISTIC(DepScanClangModuleQueries,
+          "# of times the dependency scanner performed a named lookup of a Clang module");
+
 static void findPath_dfs(ModuleDependencyID X, ModuleDependencyID Y,
                          ModuleDependencyIDSet &visited,
                          std::vector<ModuleDependencyID> &stack,
@@ -299,6 +306,7 @@ ModuleDependencyScanningWorker::ModuleDependencyScanningWorker(
 SwiftModuleScannerQueryResult
 ModuleDependencyScanningWorker::scanFilesystemForSwiftModuleDependency(
     Identifier moduleName, bool isTestableImport) {
+  DepScanSwiftModuleQueries++;
   return swiftModuleScannerLoader->lookupSwiftModule(moduleName,
                                                      isTestableImport);
 }
@@ -309,6 +317,7 @@ ModuleDependencyScanningWorker::scanFilesystemForClangModuleDependency(
     LookupModuleOutputCallback lookupModuleOutput,
     const llvm::DenseSet<clang::tooling::dependencies::ModuleID>
         &alreadySeenModules) {
+  DepScanClangModuleQueries++;
   auto clangModuleDependencies = clangScanningTool.getModuleDependencies(
       moduleName.str(), clangScanningModuleCommandLineArgs,
       clangScanningWorkingDirectoryPath, alreadySeenModules,
diff --git a/test/ScanDependencies/basic_query_stats.swift b/test/ScanDependencies/basic_query_stats.swift
new file mode 100644
index 0000000000000..1b7ac2adfba92
--- /dev/null
+++ b/test/ScanDependencies/basic_query_stats.swift
@@ -0,0 +1,39 @@
+// REQUIRES: asserts
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/module-cache)
+// RUN: %empty-directory(%t/inputs)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -scan-dependencies -module-name Test -module-cache-path %t/module-cache -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib %t/test.swift -o %t/deps.json -I %t/inputs -print-stats &> %t/stats.txt
+// RUN: cat %t/stats.txt | %FileCheck %s
+
+// Ensure that despite being a common dependency to multiple Swift modules, only 1 query is performed to find 'C'
+// CHECK: ... Statistics Collected ...
+// CHECK:    1 DependencyScanner - # of times the dependency scanner performed a named lookup of a Clang module
+
+//--- test.swift
+import A
+import B
+public func test() {}
+
+//--- inputs/A.swiftinterface
+// swift-interface-format-version: 1.0
+// swift-module-flags: -module-name A -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib -user-module-version 1.0
+import C
+public func a() { }
+
+//--- inputs/B.swiftinterface
+// swift-interface-format-version: 1.0
+// swift-module-flags: -module-name B -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib -user-module-version 1.0
+import C
+public func b() { }
+
+//--- inputs/c.h
+void c(void);
+
+//--- inputs/module.modulemap
+module C {
+  header "C.h"
+  export *
+}
+