[clang] 5a339b0 - [clang] Only set non-empty bypass to scan VFS (#159605)

[via cfe-commits]

Author: Jan Svoboda
Date: 2025-09-18T10:51:21-07:00
New Revision: 5a339b074e625a7e9c92ae98b93a2bb5e1ae9524

URL: https://github.com/llvm/llvm-project/commit/5a339b074e625a7e9c92ae98b93a2bb5e1ae9524
DIFF: https://github.com/llvm/llvm-project/commit/5a339b074e625a7e9c92ae98b93a2bb5e1ae9524.diff

LOG: [clang] Only set non-empty bypass to scan VFS (#159605)

Normalizing an empty modules cache path results in an incorrect
non-empty path (the working directory). This PR conditionalizes more
code to avoid this. Tested downstream by swift/llvm-project and the
`DependencyScanningCAPITests.DependencyScanningFSCacheOutOfDate` unit
test.

Added: 
    

Modified: 
    clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

Removed: 
    


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diff  --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
index 0a12c479bf8e3..16cb56fddc006 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -445,13 +445,14 @@ class DependencyScanningAction {
 
     // Use the dependency scanning optimized file system if requested to do so.
     if (DepFS) {
-      SmallString<256> ModulesCachePath;
-      normalizeModuleCachePath(
-          *FileMgr, ScanInstance.getHeaderSearchOpts().ModuleCachePath,
-          ModulesCachePath);
       DepFS->resetBypassedPathPrefix();
-      if (!ModulesCachePath.empty())
+      if (!ScanInstance.getHeaderSearchOpts().ModuleCachePath.empty()) {
+        SmallString<256> ModulesCachePath;
+        normalizeModuleCachePath(
+            *FileMgr, ScanInstance.getHeaderSearchOpts().ModuleCachePath,
+            ModulesCachePath);
         DepFS->setBypassedPathPrefix(ModulesCachePath);
+      }
 
       ScanInstance.setDependencyDirectivesGetter(
           std::make_unique<ScanningDependencyDirectivesGetter>(*FileMgr));