[clang] Prevent creation of new submodules in ASTWriter

Avoid inferring new submodules for headers in ASTWriter's collection of
affecting modulemap files, since we don't want to pick up dependencies
that didn't actually exist during parsing.

rdar://109112624

Differential Revision: https://reviews.llvm.org/D150151

clang/include/clang/Lex/HeaderSearch.h

@@ -665,9 +665,13 @@ public:
 
   /// Retrieve all the modules corresponding to the given file.
   ///
+  /// \param AllowCreation Whether to allow inference of a new submodule, or to
+  ///        only return existing known modules.
+  ///
   /// \ref findModuleForHeader should typically be used instead of this.
   ArrayRef<ModuleMap::KnownHeader>
-  findAllModulesForHeader(const FileEntry *File) const;
+  findAllModulesForHeader(const FileEntry *File,
+                          bool AllowCreation = true) const;
 
   /// Read the contents of the given module map file.
   ///

clang/include/clang/Lex/ModuleMap.h

@@ -448,9 +448,13 @@ public:
   /// and does not consult the external source. (Those checks are the
   /// responsibility of \ref HeaderSearch.)
   ///
+  /// \param AllowCreation Whether to allow inference of a new submodule, or to
+  ///        only return existing known modules.
+  ///
   /// Typically, \ref findModuleForHeader should be used instead, as it picks
   /// the preferred module for the header.
-  ArrayRef<KnownHeader> findAllModulesForHeader(const FileEntry *File);
+  ArrayRef<KnownHeader> findAllModulesForHeader(const FileEntry *File,
+                                                bool AllowCreation = true);
 
   /// Like \ref findAllModulesForHeader, but do not attempt to infer module
   /// ownership from umbrella headers if we've not already done so.

clang/lib/Lex/HeaderSearch.cpp

@@ -1565,13 +1565,14 @@ HeaderSearch::findModuleForHeader(const FileEntry *File, bool AllowTextual,
 }
 
 ArrayRef<ModuleMap::KnownHeader>
-HeaderSearch::findAllModulesForHeader(const FileEntry *File) const {
+HeaderSearch::findAllModulesForHeader(const FileEntry *File,
+                                      bool AllowCreation) const {
   if (ExternalSource) {
     // Make sure the external source has handled header info about this file,
     // which includes whether the file is part of a module.
     (void)getExistingFileInfo(File);
   }
-  return ModMap.findAllModulesForHeader(File);
+  return ModMap.findAllModulesForHeader(File, AllowCreation);
 }
 
 static bool suggestModule(HeaderSearch &HS, const FileEntry *File,

clang/lib/Lex/ModuleMap.cpp

@@ -683,12 +683,12 @@ ModuleMap::findOrCreateModuleForHeaderInUmbrellaDir(const FileEntry *File) {
 }
 
 ArrayRef<ModuleMap::KnownHeader>
-ModuleMap::findAllModulesForHeader(const FileEntry *File) {
+ModuleMap::findAllModulesForHeader(const FileEntry *File, bool AllowCreation) {
   HeadersMap::iterator Known = findKnownHeader(File);
   if (Known != Headers.end())
     return Known->second;
 
-  if (findOrCreateModuleForHeaderInUmbrellaDir(File))
+  if (AllowCreation && findOrCreateModuleForHeaderInUmbrellaDir(File))
     return Headers.find(File)->second;
 
   return std::nullopt;

clang/lib/Serialization/ASTWriter.cpp

@@ -185,7 +185,8 @@ std::set<const FileEntry *> GetAffectingModuleMaps(const Preprocessor &PP,
     if (!HFI || (HFI->isModuleHeader && !HFI->isCompilingModuleHeader))
       continue;
 
-    for (const auto &KH : HS.findAllModulesForHeader(File)) {
+    for (const auto &KH :
+         HS.findAllModulesForHeader(File, /*AllowCreation=*/false)) {
       if (!KH.getModule())
         continue;
       ModulesToProcess.push_back(KH.getModule());