FASTBuild: use UnityInputExcludedFiles for unity skips

Prefer it over `UnityInputIsolatedFiles` to enable caching for the
files.

Fixes: #27784

Source/cmFastbuildNormalTargetGenerator.cxx

@@ -1413,8 +1413,8 @@ void cmFastbuildNormalTargetGenerator::GenerateObjects(FastbuildTarget& target)
     useUnity = false;
   }
 
-  // List of sources isolated from the unity build if enabled.
-  std::set<std::string> isolatedFromUnity;
+  // List of sources excluded from the unity build if enabled.
+  std::set<std::string> excludedFromUnity;
 
   // Mapping from unity group (if any) to sources belonging to that group.
   std::map<std::string, std::vector<std::string>> sourcesWithGroups;
@@ -1425,10 +1425,10 @@ void cmFastbuildNormalTargetGenerator::GenerateObjects(FastbuildTarget& target)
     std::string const pathToFile = srcFile.GetFullPath();
     bool fileUsesUnity = useUnity;
     if (useUnity) {
-      // Check if the source should be added to "UnityInputIsolatedFiles".
+      // Check if the source should be added to "UnityInputExcludedFiles".
       if (srcFile.GetPropertyAsBool(SKIP_UNITY_BUILD_INCLUSION)) {
         fileUsesUnity = false;
-        isolatedFromUnity.emplace(pathToFile);
+        excludedFromUnity.emplace(pathToFile);
       }
       std::string const perFileUnityGroup =
         srcFile.GetSafeProperty(UNITY_GROUP);
@@ -1567,27 +1567,27 @@ void cmFastbuildNormalTargetGenerator::GenerateObjects(FastbuildTarget& target)
   }
   if (useUnity) {
     target.UnityNodes =
-      GenerateUnity(objects, isolatedFromUnity, sourcesWithGroups);
+      GenerateUnity(objects, excludedFromUnity, sourcesWithGroups);
   }
 }
 
 FastbuildUnityNode cmFastbuildNormalTargetGenerator::GetOneUnity(
-  std::set<std::string> const& isolatedFiles, std::vector<std::string>& files,
+  std::set<std::string> const& excludedFiles, std::vector<std::string>& files,
   int unitySize) const
 {
   FastbuildUnityNode result;
   for (auto iter = files.begin(); iter != files.end();) {
     std::string pathToFile = std::move(*iter);
     iter = files.erase(iter);
-    // This source must be isolated
-    if (isolatedFiles.find(pathToFile) != isolatedFiles.end()) {
+    // This source must be excluded from the generated unity file.
+    if (excludedFiles.find(pathToFile) != excludedFiles.end()) {
       result.UnityInputFiles.emplace_back(pathToFile);
-      result.UnityInputIsolatedFiles.emplace_back(std::move(pathToFile));
+      result.UnityInputExcludedFiles.emplace_back(std::move(pathToFile));
     } else {
       result.UnityInputFiles.emplace_back(std::move(pathToFile));
     }
     if (int(result.UnityInputFiles.size() -
-            result.UnityInputIsolatedFiles.size()) == unitySize) {
+            result.UnityInputExcludedFiles.size()) == unitySize) {
       break;
     }
   }
@@ -1617,7 +1617,7 @@ int cmFastbuildNormalTargetGenerator::GetUnityBatchSize() const
 std::vector<FastbuildUnityNode>
 cmFastbuildNormalTargetGenerator::GenerateUnity(
   std::vector<FastbuildObjectListNode>& objects,
-  std::set<std::string> const& isolatedSources,
+  std::set<std::string> const& excludedSources,
   std::map<std::string, std::vector<std::string>> const& sourcesWithGroups)
 {
   int const unitySize = GetUnityBatchSize();
@@ -1650,14 +1650,14 @@ cmFastbuildNormalTargetGenerator::GenerateUnity(
     // General unity batching of the remaining (non-grouped) sources.
     while (!obj.CompilerInputFiles.empty()) {
       FastbuildUnityNode node =
-        GetOneUnity(isolatedSources, obj.CompilerInputFiles, unitySize);
+        GetOneUnity(excludedSources, obj.CompilerInputFiles, unitySize);
       node.Name = cmStrCat(this->GetName(), "_Unity_", ++unityNumber);
       node.UnityOutputPath = obj.CompilerOutputPath;
       node.UnityOutputPattern = cmStrCat(node.Name, ext);
 
-      // Unity group of size 1 doesn't make sense - just isolate the source.
+      // Unity group of size 1 doesn't make sense - just exclude the source.
       if (groupedNode.UnityInputFiles.size() == 1) {
-        node.UnityInputIsolatedFiles.emplace_back(
+        node.UnityInputExcludedFiles.emplace_back(
           groupedNode.UnityInputFiles[0]);
         node.UnityInputFiles.emplace_back(
           std::move(groupedNode.UnityInputFiles[0]));

Source/cmFastbuildNormalTargetGenerator.h

@@ -76,14 +76,14 @@ private:
                                       std::string& args) const;
   void GenerateCudaDeviceLink(FastbuildTarget& target) const;
   void GenerateObjects(FastbuildTarget& target);
-  FastbuildUnityNode GetOneUnity(std::set<std::string> const& isolatedFiles,
+  FastbuildUnityNode GetOneUnity(std::set<std::string> const& excludedFiles,
                                  std::vector<std::string>& files,
                                  int unitySize) const;
 
   int GetUnityBatchSize() const;
   std::vector<FastbuildUnityNode> GenerateUnity(
     std::vector<FastbuildObjectListNode>& objects,
-    std::set<std::string> const& isolatedSources,
+    std::set<std::string> const& excludedSources,
     std::map<std::string, std::vector<std::string>> const& sourcesWithGroups);
   FastbuildUnityNode GenerateGroupedUnityNode(
     std::vector<std::string>& inputFiles,

Source/cmGlobalFastbuildGenerator.cxx

@@ -1201,9 +1201,9 @@ void cmGlobalFastbuildGenerator::WriteUnity(FastbuildUnityNode const& Unity)
     WriteVariable("UnityOutputPath", Quote(Unity.UnityOutputPath), 2);
     WriteVariable("UnityOutputPattern", Quote(Unity.UnityOutputPattern), 2);
     WriteArray("UnityInputFiles", Wrap(Unity.UnityInputFiles), 2);
-    if (!Unity.UnityInputIsolatedFiles.empty()) {
-      WriteArray("UnityInputIsolatedFiles",
-                 Wrap(Unity.UnityInputIsolatedFiles), 2);
+    if (!Unity.UnityInputExcludedFiles.empty()) {
+      WriteArray("UnityInputExcludedFiles",
+                 Wrap(Unity.UnityInputExcludedFiles), 2);
     }
     if (UsingRelativePaths) {
       WriteVariable("UseRelativePaths_Experimental", "true", 2);

Source/cmGlobalFastbuildGenerator.h

@@ -233,7 +233,7 @@ struct FastbuildUnityNode : public FastbuildTargetBase
   std::string UnityOutputPath;
   std::vector<std::string> UnityInputFiles;
   std::string UnityOutputPattern;
-  std::vector<std::string> UnityInputIsolatedFiles;
+  std::vector<std::string> UnityInputExcludedFiles;
   FastbuildUnityNode()
     : FastbuildTargetBase(FastbuildTargetType::UNITY)
   {

Tests/RunCMake/FASTBuild/UnityIsolate-check.cmake

@@ -10,7 +10,7 @@ set(REGEX_TO_MATCH "
       '.*some_source_file_3.cpp',
       '.*some_source_file_4.cpp'
     }
-    .UnityInputIsolatedFiles =
+    .UnityInputExcludedFiles =
     {
       '.*some_source_file_1.cpp',
       '.*some_source_file_4.cpp'