1 files changed, 14 insertions, 5 deletions
diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.h b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
index 8297db1eaf4..84b17422db5 100644
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.h
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_GLOBALCOMPILATIONDATABASE_H
 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_GLOBALCOMPILATIONDATABASE_H
 
+#include "Function.h"
 #include "Path.h"
 #include "llvm/ADT/StringMap.h"
 #include <memory>
@@ -41,8 +42,15 @@ public:
   /// Clangd should treat the results as unreliable.
   virtual tooling::CompileCommand getFallbackCommand(PathRef File) const;
 
-  /// FIXME(ibiryukov): add facilities to track changes to compilation flags of
-  /// existing targets.
+  using CommandChanged = Event<std::vector<std::string>>;
+  /// The callback is notified when files may have new compile commands.
+  /// The argument is a list of full file paths.
+  CommandChanged::Subscription watch(CommandChanged::Listener L) const {
+    return OnCommandChanged.observe(std::move(L));
+  }
+
+protected:
+  mutable CommandChanged OnCommandChanged;
 };
 
 /// Gets compile args from tooling::CompilationDatabases built for parent
@@ -61,7 +69,8 @@ public:
 
 private:
   tooling::CompilationDatabase *getCDBForFile(PathRef File) const;
-  tooling::CompilationDatabase *getCDBInDirLocked(PathRef File) const;
+  std::pair<tooling::CompilationDatabase *, /*Cached*/ bool>
+  getCDBInDirLocked(PathRef File) const;
 
   mutable std::mutex Mutex;
   /// Caches compilation databases loaded from directories(keys are
@@ -81,8 +90,7 @@ public:
   // Base may be null, in which case no entries are inherited.
   // FallbackFlags are added to the fallback compile command.
   OverlayCDB(const GlobalCompilationDatabase *Base,
-             std::vector<std::string> FallbackFlags = {})
-      : Base(Base), FallbackFlags(std::move(FallbackFlags)) {}
+             std::vector<std::string> FallbackFlags = {});
 
   llvm::Optional<tooling::CompileCommand>
   getCompileCommand(PathRef File) const override;
@@ -98,6 +106,7 @@ private:
   llvm::StringMap<tooling::CompileCommand> Commands; /* GUARDED_BY(Mut) */
   const GlobalCompilationDatabase *Base;
   std::vector<std::string> FallbackFlags;
+  CommandChanged::Subscription BaseChanged;
 };
 
 } // namespace clangd