[clang] Report the on-disk paths for inputs to module compiles

[jansvoboda11]

Summary

Since D135636, PCM files contain the "as requested" path of input files. The machinery for generating dependency files reports those paths as they appeared in the PCM file, which may confuse consumers that are not aware of VFS overlays that might've been in place at compile-time.

This patch makes sure the "use-external-name" setting is being respected when generating dependency files in modular builds by piping the paths serialized in PCMs through FileEntryRef::getName() before putting them into dependency files.

rdar://103459532

[benlangmuir]

Please add a comment to each place you're doing this since it's non-obvious why the filename would be different to people not familiar with the mapping code. Otherwise LGTM

[jansvoboda11]

Fix test on Windows(?), add comment

clang/lib/Frontend/DependencyFile.cpp

DepCollector.maybeAddDependency(Filename, /*FromModule*/false,
                                     /*IsSystem*/IsSystem,
                                     /*IsModuleFile*/false,
                                     /*IsMissing*/false);
   }
 };
 
 struct DepCollectorASTListener : public ASTReaderListener {
   DependencyCollector &DepCollector;
-  DepCollectorASTListener(DependencyCollector &L) : DepCollector(L) { }
+  FileManager &FileMgr;
+  DepCollectorASTListener(DependencyCollector &L, FileManager &FileMgr)
+      : DepCollector(L), FileMgr(FileMgr) {}
   bool needsInputFileVisitation() override { return true; }
   bool needsSystemInputFileVisitation() override {
     return DepCollector.needSystemDependencies();
   }
   void visitModuleFile(StringRef Filename,
                        serialization::ModuleKind Kind) override {
     DepCollector.maybeAddDependency(Filename, /*FromModule*/true,
                                    /*IsSystem*/false, /*IsModuleFile*/true,
                                    /*IsMissing*/false);
   }
   bool visitInputFile(StringRef Filename, bool IsSystem,
                       bool IsOverridden, bool IsExplicitModule) override {
     if (IsOverridden || IsExplicitModule)
       return true;
 
+    // Run this through the FileManager in order to respect 'use-external-name'
+    // in case we have a VFS overlay.
+    if (auto FE = FileMgr.getOptionalFileRef(Filename))
+      Filename = FE->getName();
+
     DepCollector.maybeAddDependency(Filename, /*FromModule*/true, IsSystem,
                                    /*IsModuleFile*/false, /*IsMissing*/false);
     return true;
   }
 };
 } // end anonymous namespace
 
 void DependencyCollector::maybeAddDependency(StringRef Filename,

 
 DependencyCollector::~DependencyCollector() { }
 void DependencyCollector::attachToPreprocessor(Preprocessor &PP) {
   PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(*this, PP));
   PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
       std::make_unique<DepCollectorMMCallbacks>(*this));
 }
 void DependencyCollector::attachToASTReader(ASTReader &R) {
-  R.addListener(std::make_unique<DepCollectorASTListener>(*this));
+  R.addListener(
+      std::make_unique<DepCollectorASTListener>(*this, R.getFileManager()));
 }
 
 DependencyFileGenerator::DependencyFileGenerator(
     const DependencyOutputOptions &Opts)
     : OutputFile(Opts.OutputFile), Targets(Opts.Targets),
       IncludeSystemHeaders(Opts.IncludeSystemHeaders),
       PhonyTarget(Opts.UsePhonyTargets),
       AddMissingHeaderDeps(Opts.AddMissingHeaderDeps), SeenMissingHeader(false),

clang/lib/Frontend/ModuleDependencyCollector.cpp

 #include "llvm/Support/raw_ostream.h"
 
 using namespace clang;
 
 namespace {
 /// Private implementations for ModuleDependencyCollector
 class ModuleDependencyListener : public ASTReaderListener {
   ModuleDependencyCollector &Collector;
+  FileManager &FileMgr;
 public:
-  ModuleDependencyListener(ModuleDependencyCollector &Collector)
-      : Collector(Collector) {}
+  ModuleDependencyListener(ModuleDependencyCollector &Collector,
+                           FileManager &FileMgr)
+      : Collector(Collector), FileMgr(FileMgr) {}
   bool needsInputFileVisitation() override { return true; }
   bool needsSystemInputFileVisitation() override { return true; }
   bool visitInputFile(StringRef Filename, bool IsSystem, bool IsOverridden,
                       bool IsExplicitModule) override {
+    // Run this through the FileManager in order to respect 'use-external-name'
+    // in case we have a VFS overlay.
+    if (auto FE = FileMgr.getOptionalFileRef(Filename))
+      Filename = FE->getName();
     Collector.addFile(Filename);
     return true;
   }
 };
 
 struct ModuleDependencyPPCallbacks : public PPCallbacks {
   ModuleDependencyCollector &Collector;
   SourceManager &SM;
if (!UmbrellaDir.equals(UmbreallDirFromHeader)) {
         moduleMapAddHeader(AltHeaderFilename);
     }
   }
 };
 
 }
 
 void ModuleDependencyCollector::attachToASTReader(ASTReader &R) {
-  R.addListener(std::make_unique<ModuleDependencyListener>(*this));
+  R.addListener(
+      std::make_unique<ModuleDependencyListener>(*this, R.getFileManager()));
 }
 
 void ModuleDependencyCollector::attachToPreprocessor(Preprocessor &PP) {
   PP.addPPCallbacks(std::make_unique<ModuleDependencyPPCallbacks>(
       *this, PP.getSourceManager()));
   PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
       std::make_unique<ModuleDependencyMMCallbacks>(*this));
 }

clang/test/Modules/dependency-gen-vfs.c

+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- module.modulemap
+module M { header "m.h" }
+
+//--- m-real.h
+
+//--- overlay.json.template
+{
+  "version": 0,
+  "case-sensitive": "false",
+  "roots": [
+    {
+      "external-contents": "DIR/m-real.h",
+      "name": "DIR/m.h",
+      "type": "file"
+    }
+  ]
+}
+
+//--- tu.c
+#include "m.h"
+
+// RUN: sed -e "s|DIR|%/t|g" %t/overlay.json.template > %t/overlay.json
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache \
+// RUN:   -ivfsoverlay %t/overlay.json -dependency-file %t/tu.d -MT %t/tu.o -fsyntax-only %t/tu.c
+// RUN: FileCheck %s --input-file=%t/tu.d
+// CHECK:      {{.*}}tu.o: \
+// CHECK-NEXT: {{.*}}tu.c \
+// CHECK-NEXT: {{.*}}module.modulemap \
+// CHECK-NEXT: {{.*}}m-real.h