[clang] [clang][modules] Allow module maps with textual headers to be non-affecting (PR #89441)

[Sam McCall via cfe-commits]

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@@ -187,7 +187,8 @@ GetAffectingModuleMaps(const Preprocessor &PP, Module *RootModule) {
       continue;
 
     const HeaderFileInfo *HFI = HS.getExistingLocalFileInfo(*File);
-    if (!HFI || (HFI->isModuleHeader && !HFI->isCompilingModuleHeader))
+    if (!HFI || (HFI->isModuleHeader && !HFI->isCompilingModuleHeader) ||
+        (HFI->isTextualModuleHeader && !PP.alreadyIncluded(*File)))
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sam-mccall wrote:

That makes sense, I don't have any intuition for whether it's necessary or not.

Shortcutting this analysis seems like a useful change of possible, but I think restoring the previous behavior is a helpful starting point.

https://github.com/llvm/llvm-project/pull/89441