Propagate vfs overlays and -fbuiltin-headers-in-system-modules

This fixes explicit module builds for a hello world program on Windows
as well as the ucrt import build failure as in the included test.

Author: hjyamauchi

include/swift/ClangImporter/ClangImporter.h

@@ -199,11 +199,14 @@ class ClangImporter final : public ClangModuleLoader {
          bool ignoreFileMapping = false);
 
   static std::vector<std::string>
-  getClangDriverArguments(ASTContext &ctx, bool ignoreClangTarget = false);
+  getClangDriverArguments(ASTContext &ctx,
+                          bool requiresBuiltinHeadersInSystemModules = false,
+                          bool ignoreClangTarget = false);
 
   static std::optional<std::vector<std::string>>
   getClangCC1Arguments(ClangImporter *importer, ASTContext &ctx,
                        llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+                       bool requiresBuiltinHeadersInSystemModules = false,
                        bool ignoreClangTarget = false);
 
   static std::unique_ptr<clang::CompilerInvocation>

lib/ClangImporter/ClangImporter.cpp

@@ -789,7 +789,8 @@ getEmbedBitcodeInvocationArguments(std::vector<std::string> &invocationArgStrs,
 void
 importer::addCommonInvocationArguments(
     std::vector<std::string> &invocationArgStrs,
-    ASTContext &ctx, bool ignoreClangTarget) {
+    ASTContext &ctx, bool requiresBuiltinHeadersInSystemModules,
+    bool ignoreClangTarget) {
   using ImporterImpl = ClangImporter::Implementation;
   llvm::Triple triple = ctx.LangOpts.Target;
   // Use clang specific target triple if given.
@@ -957,6 +958,18 @@ importer::addCommonInvocationArguments(
       }
     }
   }
+
+  for (auto &overlay : searchPathOpts.VFSOverlayFiles) {
+    invocationArgStrs.push_back("-ivfsoverlay");
+    invocationArgStrs.push_back(overlay);
+  }
+
+  ClangInvocationFileMapping fileMapping =
+      getClangInvocationFileMapping(ctx, nullptr, /*supressDiagnostic*/true);
+  if (fileMapping.requiresBuiltinHeadersInSystemModules) {
+    invocationArgStrs.push_back("-Xclang");
+    invocationArgStrs.push_back("-fbuiltin-headers-in-system-modules");
+  }
 }
 
 bool ClangImporter::canReadPCH(StringRef PCHFilename) {
@@ -1124,7 +1137,8 @@ ClangImporter::getOrCreatePCH(const ClangImporterOptions &ImporterOptions,
 }
 
 std::vector<std::string>
-ClangImporter::getClangDriverArguments(ASTContext &ctx, bool ignoreClangTarget) {
+ClangImporter::getClangDriverArguments(ASTContext &ctx,
+    bool requiresBuiltinHeadersInSystemModules, bool ignoreClangTarget) {
   assert(!ctx.ClangImporterOpts.DirectClangCC1ModuleBuild &&
          "direct-clang-cc1-module-build should not call this function");
   std::vector<std::string> invocationArgStrs;
@@ -1140,14 +1154,15 @@ ClangImporter::getClangDriverArguments(ASTContext &ctx, bool ignoreClangTarget)
     getEmbedBitcodeInvocationArguments(invocationArgStrs, ctx);
     break;
   }
-  addCommonInvocationArguments(invocationArgStrs, ctx, ignoreClangTarget);
+  addCommonInvocationArguments(invocationArgStrs, ctx,
+      requiresBuiltinHeadersInSystemModules, ignoreClangTarget);
   return invocationArgStrs;
 }
 
 std::optional<std::vector<std::string>> ClangImporter::getClangCC1Arguments(
     ClangImporter *importer, ASTContext &ctx,
     llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
-    bool ignoreClangTarget) {
+    bool requiresBuiltinHeadersInSystemModules, bool ignoreClangTarget) {
   std::unique_ptr<clang::CompilerInvocation> CI;
 
   // Set up a temporary diagnostic client to report errors from parsing the
@@ -1210,7 +1225,8 @@ std::optional<std::vector<std::string>> ClangImporter::getClangCC1Arguments(
     CI->getFrontendOpts().IndexStorePath = ctx.ClangImporterOpts.IndexStorePath;
   } else {
     // Otherwise, create cc1 arguments from driver args.
-    auto driverArgs = getClangDriverArguments(ctx, ignoreClangTarget);
+    auto driverArgs = getClangDriverArguments(ctx,
+        requiresBuiltinHeadersInSystemModules, ignoreClangTarget);
 
     llvm::SmallVector<const char *> invocationArgs;
     invocationArgs.reserve(driverArgs.size());
@@ -1370,14 +1386,12 @@ ClangImporter::create(ASTContext &ctx,
 
   // Create a new Clang compiler invocation.
   {
-    if (auto ClangArgs = getClangCC1Arguments(importer.get(), ctx, VFS))
+    if (auto ClangArgs = getClangCC1Arguments(importer.get(), ctx, VFS,
+            fileMapping.requiresBuiltinHeadersInSystemModules))
       importer->Impl.ClangArgs = *ClangArgs;
     else
       return nullptr;
 
-    if (fileMapping.requiresBuiltinHeadersInSystemModules)
-      importer->Impl.ClangArgs.push_back("-fbuiltin-headers-in-system-modules");
-
     ArrayRef<std::string> invocationArgStrs = importer->Impl.ClangArgs;
     if (importerOpts.DumpClangDiagnostics) {
       llvm::errs() << "clang importer cc1 args: '";
@@ -1465,8 +1479,9 @@ ClangImporter::create(ASTContext &ctx,
   if (ctx.LangOpts.ClangTarget.has_value()) {
     // If '-clang-target' is set, create a mock invocation with the Swift triple
     // to configure CodeGen and Target options for Swift compilation.
-    auto swiftTargetClangArgs =
-        getClangCC1Arguments(importer.get(), ctx, VFS, true);
+    auto swiftTargetClangArgs = getClangCC1Arguments(importer.get(), ctx, VFS,
+        /*requiresBuiltinHeadersInSystemModulestrue*/false,
+        /*ignoreClangTarget*/true);
     if (!swiftTargetClangArgs)
       return nullptr;
     auto swiftTargetClangInvocation = createClangInvocation(

lib/ClangImporter/ImporterImpl.h

@@ -1914,6 +1914,7 @@ void getNormalInvocationArguments(std::vector<std::string> &invocationArgStrs,
 /// Add command-line arguments common to all imports of Clang code.
 void addCommonInvocationArguments(std::vector<std::string> &invocationArgStrs,
                                   ASTContext &ctx,
+                                  bool requiresBuiltinHeadersInSystemModules,
                                   bool ignoreClangTarget);
 
 /// Finds a particular kind of nominal by looking through typealiases.

test/ScanDependencies/win-crt.swift

@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -scan-dependencies -Xcc -v %s -o - | %validate-json | %FileCheck %s
+
+// We want to explicitly import WinSDK's CRT.
+// REQUIRES: OS=windows-msvc
+
+import CRT
+
+// CHECK:        "modulePath": "{{.*}}\\ucrt-{{.*}}.pcm",
+// CHECK-NEXT:   "sourceFiles": [
+// CHECK-NEXT:      "{{.*}}\\ucrt\\module.modulemap"