[clang][modules][deps] Parse "FW_Private" module map even after loading "FW" PCM

[jansvoboda11]

Summary

When Clang loads a PCM that depends on another PCM describing framework module "FW", ModuleMap registers "FW" as known, without seeing the module map that defines it (or the adjacent "FW_Private" module map). Later, when looking at a header from "FW_Private", ModuleMap returns early due to having knowledge about "FW" and never associates that header with "FW_Private", leading to it being treated as textual. This behavior is caused by D150292, where the scanner stops calling HeaderSearch::lookupModule() eagerly for every loaded PCM.

This patch skips an early check when trying to figure out the framework module for a header, which ensures the "FW" and (most importantly) "FW_Private" module maps can be parsed even after loading "FW" from a PCM. Note that the HeaderSearch::loadModuleMapFile() function we not call unconditionally has caching behavior of its own, meaning it will avoid parsing module map file repeatedly.

Depends on D150320.

[jansvoboda11]

clang/lib/Lex/HeaderSearch.cpp

1795

We should probably break for LMM_AlreadyLoaded instead of returning null.

[benlangmuir]

LGTM. I ran into a similar issue in a downstream branch

[jansvoboda11]

Expose new preprocessor option as a -cc1 flag, move test from ClangScanDeps to Modules directory.

clang/include/clang/Driver/Options.td

 defm modules_search_all : BoolFOption<"modules-search-all",
   LangOpts<"ModulesSearchAll">, DefaultFalse,
   PosFlag<SetTrue, [], "Search even non-imported modules to resolve references">,
   NegFlag<SetFalse>, BothFlags<[NoXarchOption, CC1Option,CoreOption]>>,
   ShouldParseIf<fmodules.KeyPath>;
 defm implicit_modules : BoolFOption<"implicit-modules",
   LangOpts<"ImplicitModules">, DefaultTrue,
   NegFlag<SetFalse, [CC1Option]>, PosFlag<SetTrue>, BothFlags<[NoXarchOption,CoreOption]>>;
+def fno_modules_check_relocated : Joined<["-"], "fno-modules-check-relocated">,
+  Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Skip checks for relocated modules when loading PCM files">,
+  MarshallingInfoNegativeFlag<PreprocessorOpts<"ModulesCheckRelocated">>;
 def fretain_comments_from_system_headers : Flag<["-"], "fretain-comments-from-system-headers">, Group<f_Group>, Flags<[CC1Option]>,
   MarshallingInfoFlag<LangOpts<"RetainCommentsFromSystemHeaders">>;
 def fmodule_header : Flag <["-"], "fmodule-header">, Group<f_Group>,
   Flags<[NoXarchOption]>, HelpText<"Build a C++20 Header Unit from a header.">;
 def fmodule_header_EQ : Joined<["-"], "fmodule-header=">, Group<f_Group>,
   Flags<[NoXarchOption]>, MetaVarName<"<kind>">,
   HelpText<"Build a C++20 Header Unit from a header that should be found in the user (fmodule-header=user) or system (fmodule-header=system) search path.">;
 

clang/lib/Lex/HeaderSearch.cpp

if (IsFramework) {
     if (auto F = FileMgr.getOptionalFileRef(ModuleMapFileName))
       return *F;
   }
   return std::nullopt;
 }
 
 Module *HeaderSearch::loadFrameworkModule(StringRef Name, DirectoryEntryRef Dir,
                                           bool IsSystem) {
-  if (Module *Module = ModMap.findModule(Name))
-    return Module;
-
   // Try to load a module map file.
   switch (loadModuleMapFile(Dir, IsSystem, /*IsFramework*/true)) {
   case LMM_InvalidModuleMap:
     // Try to infer a module map from the framework directory.
     if (HSOpts->ImplicitModuleMaps)
       ModMap.inferFrameworkModule(Dir, IsSystem, /*Parent=*/nullptr);
     break;
 
-  case LMM_AlreadyLoaded:
   case LMM_NoDirectory:
     return nullptr;
 
+  case LMM_AlreadyLoaded:
   case LMM_NewlyLoaded:
     break;
   }
 
   return ModMap.findModule(Name);
 }
 
 HeaderSearch::LoadModuleMapResult

clang/test/Modules/no-check-relocated-fw-private.c

+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- frameworks1/FW1.framework/Modules/module.modulemap
+framework module FW1 { header "FW1.h" }
+//--- frameworks1/FW1.framework/Headers/FW1.h
+#import <FW2/FW2.h>
+
+//--- frameworks2/FW2.framework/Modules/module.modulemap
+framework module FW2 { header "FW2.h" }
+//--- frameworks2/FW2.framework/Modules/module.private.modulemap
+framework module FW2_Private { header "FW2_Private.h" }
+//--- frameworks2/FW2.framework/Headers/FW2.h
+//--- frameworks2/FW2.framework/PrivateHeaders/FW2_Private.h
+
+//--- tu.c
+#import <FW1/FW1.h>         // expected-remark{{importing module 'FW1'}} \
+                            // expected-remark{{importing module 'FW2'}}
+#import <FW2/FW2_Private.h> // expected-remark{{importing module 'FW2_Private'}}
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t/cache -fimplicit-module-maps \
+// RUN:   -F %t/frameworks1 -F %t/frameworks2 -fsyntax-only %t/tu.c \
+// RUN:   -fno-modules-check-relocated -Rmodule-import -verify