[clang][modules] Infer framework modules in explicit builds

[jansvoboda11]

Summary

This patch enables inferring framework modules in explicit builds in all contexts. Until now, inferring framework modules only worked with -fimplicit-module-maps due to this block of code:

// HeaderSearch::loadFrameworkModule
  case LMM_InvalidModuleMap:
    // Try to infer a module map from the framework directory.
    if (HSOpts->ImplicitModuleMaps)
      ModMap.inferFrameworkModule(Dir, IsSystem, /*Parent=*/nullptr);
    break;

[Bigcheese]

I think this makes sense to do given that you need to explicitly opt into inferred modules anyway. This isn't implicitly finding module maps, as we already have a module map with framework module *.

[jansvoboda11]

Remove changes related to dependency scanning

clang/include/clang/Lex/ModuleMap.h

public:
   void finishModuleDeclarationScope() { CurrentModuleScopeID += 1; }
 
   bool mayShadowNewModule(Module *ExistingModule) {
     assert(!ExistingModule->Parent && "expected top-level module");
     assert(ModuleScopeIDs.count(ExistingModule) && "unknown module");
     return ModuleScopeIDs[ExistingModule] < CurrentModuleScopeID;
   }
 
+  /// Check whether a framework module can be inferred in the given directory.
+  bool canInferFrameworkModule(const DirectoryEntry *Dir) const {
+    auto It = InferredDirectories.find(Dir);
+    return It != InferredDirectories.end() && It->getSecond().InferModules;
+  }
+
   /// Retrieve the module map file containing the definition of the given
   /// module.
   ///
   /// \param Module The module whose module map file will be returned, if known.
   ///
   /// \returns The file entry for the module map file containing the given
   /// module, or nullptr if the module definition was inferred.
   const FileEntry *getContainingModuleMapFile(const Module *Module) const;

clang/lib/Frontend/FrontendAction.cpp

static bool loadModuleMapForModuleBuild(CompilerInstance &CI, bool IsSystem,
   // Load the module map file.
   if (HS.loadModuleMapFile(ModuleMap, IsSystem, ModuleMapID, &Offset,
                            PresumedModuleMapFile))
     return true;
 
   if (SrcMgr.getBufferOrFake(ModuleMapID).getBufferSize() == Offset)
     Offset = 0;
 
+  // Infer framework module if possible.
+  if (HS.getModuleMap().canInferFrameworkModule(ModuleMap->getDir())) {
+    SmallString<128> InferredFrameworkPath = ModuleMap->getDir()->getName();
+    llvm::sys::path::append(InferredFrameworkPath,
+                            CI.getLangOpts().ModuleName + ".framework");
+    if (auto Dir = CI.getFileManager().getDirectory(InferredFrameworkPath))
+      (void)HS.getModuleMap().inferFrameworkModule(*Dir, IsSystem, nullptr);
+  }
+
   return false;
 }
 
 static Module *prepareToBuildModule(CompilerInstance &CI,
                                     StringRef ModuleMapFilename) {
   if (CI.getLangOpts().CurrentModule.empty()) {
     CI.getDiagnostics().Report(diag::err_missing_module_name);
 

clang/test/Modules/explicit-build-inferred.cpp

 // RUN: rm -rf %t && mkdir %t
 //
-// RUN: %clang_cc1 -fmodules -fno-implicit-modules -fimplicit-module-maps \
+// RUN: %clang_cc1 -fmodules -fno-implicit-modules \
 // RUN:   -emit-module -x c++ %S/Inputs/explicit-build-inferred/frameworks/module.modulemap \
 // RUN:   -fmodule-name=Inferred -o %t/Inferred.pcm -F %S/Inputs/explicit-build-inferred/frameworks
 //
 // RUN: %clang_cc1 -fmodules -fno-implicit-modules -fsyntax-only %s \
-// RUN:   -fmodule-map-file=%S/Inputs/explicit-build-inferred/frameworks/module.modulemap \
 // RUN:   -fmodule-file=%t/Inferred.pcm -F %S/Inputs/explicit-build-inferred/frameworks
 
 #include <Inferred/Inferred.h>
 
 inferred a = 0;