[clang-tools-extra] [clangd] Add background index format support to clangd-indexer (PR #175209)

[Jason Williams via cfe-commits]

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@@ -123,6 +136,117 @@ class IndexActionFactory : public tooling::FrontendActionFactory {
   RelationSlab::Builder Relations;
 };
 
+// Action factory that writes per-file shards (for background index format).
+class BackgroundIndexActionFactory : public tooling::FrontendActionFactory {
+public:
+  BackgroundIndexActionFactory(BackgroundIndexStorage &Storage)
+      : Storage(Storage), Symbols(std::make_unique<SymbolSlab::Builder>()),
+        Refs(std::make_unique<RefSlab::Builder>()),
+        Relations(std::make_unique<RelationSlab::Builder>()) {}
+
+  std::unique_ptr<FrontendAction> create() override {
+    SymbolCollector::Options Opts;
+    Opts.CountReferences = true;
+    Opts.FileFilter = [&](const SourceManager &SM, FileID FID) {
+      const auto F = SM.getFileEntryRefForID(FID);
+      if (!F)
+        return false;
+      auto AbsPath = getCanonicalPath(*F, SM.getFileManager());
+      if (!AbsPath)
+        return false;
+      std::lock_guard<std::mutex> Lock(FilesMu);
+      return Files.insert(*AbsPath).second;
+    };
+    return createStaticIndexingAction(
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jasonwilliams wrote:

I've re-organised it into a baseclass which shares logic. Due to the membership of Symbols most of the logic is still separate but i've put the calls into the base class so its more clear what is happening

https://github.com/llvm/llvm-project/pull/175209