[clang] [clang][modules] Avoid modules diagnostics for `__has_include()` (PR #71450)

[Jan Svoboda via cfe-commits]

https://github.com/jansvoboda11 created https://github.com/llvm/llvm-project/pull/71450

After #70144 Clang started resolving module maps even for `__has_include()` expressions. The unintended consequence of this is that diagnostics related to module mis-use started trigerring. These diagnostics are clearly intended to catch actual usage of a header, so should not apply for `__has_include()` expressions that don't bring the contents of the header into the TU.


>From f66c121e698142892b4c59163cae38cd10fc1e0c Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan_svoboda at apple.com>
Date: Mon, 6 Nov 2023 13:05:23 -0800
Subject: [PATCH 1/2] Fix

---
 clang/lib/Lex/PPDirectives.cpp | 36 +++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index d97a103833c2fa6..956e2276f25b710 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -960,7 +960,6 @@ OptionalFileEntryRef Preprocessor::LookupFile(
 
   Module *RequestingModule = getModuleForLocation(
       FilenameLoc, LangOpts.ModulesValidateTextualHeaderIncludes);
-  bool RequestingModuleIsModuleInterface = !SourceMgr.isInMainFile(FilenameLoc);
 
   // If the header lookup mechanism may be relative to the current inclusion
   // stack, record the parent #includes.
@@ -1041,13 +1040,8 @@ OptionalFileEntryRef Preprocessor::LookupFile(
       Filename, FilenameLoc, isAngled, FromDir, &CurDir, Includers, SearchPath,
       RelativePath, RequestingModule, SuggestedModule, IsMapped,
       IsFrameworkFound, SkipCache, BuildSystemModule, OpenFile, CacheFailures);
-  if (FE) {
-    if (SuggestedModule && !LangOpts.AsmPreprocessor)
-      HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
-          RequestingModule, RequestingModuleIsModuleInterface, FilenameLoc,
-          Filename, *FE);
+  if (FE)
     return FE;
-  }
 
   OptionalFileEntryRef CurFileEnt;
   // Otherwise, see if this is a subframework header.  If so, this is relative
@@ -1058,10 +1052,6 @@ OptionalFileEntryRef Preprocessor::LookupFile(
       if (OptionalFileEntryRef FE = HeaderInfo.LookupSubframeworkHeader(
               Filename, *CurFileEnt, SearchPath, RelativePath, RequestingModule,
               SuggestedModule)) {
-        if (SuggestedModule && !LangOpts.AsmPreprocessor)
-          HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
-              RequestingModule, RequestingModuleIsModuleInterface, FilenameLoc,
-              Filename, *FE);
         return FE;
       }
     }
@@ -1073,10 +1063,6 @@ OptionalFileEntryRef Preprocessor::LookupFile(
         if (OptionalFileEntryRef FE = HeaderInfo.LookupSubframeworkHeader(
                 Filename, *CurFileEnt, SearchPath, RelativePath,
                 RequestingModule, SuggestedModule)) {
-          if (SuggestedModule && !LangOpts.AsmPreprocessor)
-            HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
-                RequestingModule, RequestingModuleIsModuleInterface,
-                FilenameLoc, Filename, *FE);
           return FE;
         }
       }
@@ -2027,12 +2013,28 @@ OptionalFileEntryRef Preprocessor::LookupHeaderIncludeOrImport(
     const FileEntry *LookupFromFile, StringRef &LookupFilename,
     SmallVectorImpl<char> &RelativePath, SmallVectorImpl<char> &SearchPath,
     ModuleMap::KnownHeader &SuggestedModule, bool isAngled) {
+  auto DiagnoseHeaderInclusion = [&](FileEntryRef FE) {
+    if (LangOpts.AsmPreprocessor)
+      return;
+
+    Module *RequestingModule = getModuleForLocation(
+        FilenameLoc, LangOpts.ModulesValidateTextualHeaderIncludes);
+    bool RequestingModuleIsModuleInterface =
+        !SourceMgr.isInMainFile(FilenameLoc);
+
+    HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
+        RequestingModule, RequestingModuleIsModuleInterface, FilenameLoc,
+        Filename, FE);
+  };
+
   OptionalFileEntryRef File = LookupFile(
       FilenameLoc, LookupFilename, isAngled, LookupFrom, LookupFromFile, CurDir,
       Callbacks ? &SearchPath : nullptr, Callbacks ? &RelativePath : nullptr,
       &SuggestedModule, &IsMapped, &IsFrameworkFound);
-  if (File)
+  if (File) {
+    DiagnoseHeaderInclusion(*File);
     return File;
+  }
 
   // Give the clients a chance to silently skip this include.
   if (Callbacks && Callbacks->FileNotFound(Filename))
@@ -2051,6 +2053,7 @@ OptionalFileEntryRef Preprocessor::LookupHeaderIncludeOrImport(
         &SuggestedModule, &IsMapped,
         /*IsFrameworkFound=*/nullptr);
     if (File) {
+      DiagnoseHeaderInclusion(*File);
       Diag(FilenameTok, diag::err_pp_file_not_found_angled_include_not_fatal)
           << Filename << IsImportDecl
           << FixItHint::CreateReplacement(FilenameRange,
@@ -2081,6 +2084,7 @@ OptionalFileEntryRef Preprocessor::LookupHeaderIncludeOrImport(
         Callbacks ? &RelativePath : nullptr, &SuggestedModule, &IsMapped,
         /*IsFrameworkFound=*/nullptr);
     if (File) {
+      DiagnoseHeaderInclusion(*File);
       auto Hint =
           isAngled ? FixItHint::CreateReplacement(
                          FilenameRange, "<" + TypoCorrectionName.str() + ">")

>From 961707929fe12ab78386450e04dfea541b08b9c1 Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan_svoboda at apple.com>
Date: Mon, 6 Nov 2023 13:05:26 -0800
Subject: [PATCH 2/2] Test

---
 clang/test/Modules/has_include_non_modular.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 clang/test/Modules/has_include_non_modular.c

diff --git a/clang/test/Modules/has_include_non_modular.c b/clang/test/Modules/has_include_non_modular.c
new file mode 100644
index 000000000000000..2e1a06bdc6e4a0d
--- /dev/null
+++ b/clang/test/Modules/has_include_non_modular.c
@@ -0,0 +1,14 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- module.modulemap
+module Mod { header "mod.h" }
+//--- mod.h
+#if __has_include("textual.h")
+#endif
+//--- textual.h
+
+//--- tu.c
+#include "mod.h"
+
+// RUN: %clang -fsyntax-only %t/tu.c -fmodules -fmodules-cache-path=%t/cache -Werror=non-modular-include-in-module