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

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;
```

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D113880

clang/include/clang/Lex/ModuleMap.h

@@ -584,6 +584,12 @@ public:
     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.
   ///

clang/lib/Frontend/FrontendAction.cpp

@@ -465,6 +465,15 @@ static bool loadModuleMapForModuleBuild(CompilerInstance &CI, bool IsSystem,
   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;
 }
 

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

@@ -1,11 +1,10 @@
 // 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>