[clangd] New ParsingCallback for semantics changes

Previously notification of the Server about semantic happened strictly
before notification of the AST thread.
Hence a racy Server could make a request (like semantic tokens) after
the notification, with the assumption that it'll be served fresh
content. But it wasn't true if AST thread wasn't notified about the
change yet.

This change reverses the order of those notifications to prevent racy
interactions.

Differential Revision: https://reviews.llvm.org/D102761

diff --git a/clang-tools-extra/clangd/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
index 3f8b95b..0f525f3 100644 (file)
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -75,8 +75,6 @@ struct UpdateIndexCallbacks : public ParsingCallbacks {
                      const CanonicalIncludes &CanonIncludes) override {
     if (FIndex)
       FIndex->updatePreamble(Path, Version, Ctx, std::move(PP), CanonIncludes);
-    if (ServerCallbacks)
-      ServerCallbacks->onSemanticsMaybeChanged(Path);
   }
 
   void onMainAST(PathRef Path, ParsedAST &AST, PublishFn Publish) override {
@@ -105,6 +103,11 @@ struct UpdateIndexCallbacks : public ParsingCallbacks {
       ServerCallbacks->onFileUpdated(File, Status);
   }
 
+  void onPreamblePublished(PathRef File) override {
+    if (ServerCallbacks)
+      ServerCallbacks->onSemanticsMaybeChanged(File);
+  }
+
 private:
   FileIndex *FIndex;
   ClangdServer::Callbacks *ServerCallbacks;

diff --git a/clang-tools-extra/clangd/TUScheduler.cpp b/clang-tools-extra/clangd/TUScheduler.cpp
index 435deb6..7498598 100644 (file)
--- a/clang-tools-extra/clangd/TUScheduler.cpp
+++ b/clang-tools-extra/clangd/TUScheduler.cpp
@@ -909,6 +909,7 @@ void PreambleThread::build(Request Req) {
     ASTPeer.updatePreamble(std::move(Req.CI), std::move(Req.Inputs),
                            LatestBuild, std::move(Req.CIDiags),
                            std::move(Req.WantDiags));
+    Callbacks.onPreamblePublished(FileName);
   });
 
   if (!LatestBuild || Inputs.ForceRebuild) {

diff --git a/clang-tools-extra/clangd/TUScheduler.h b/clang-tools-extra/clangd/TUScheduler.h
index 8df2c01..4731443 100644 (file)
--- a/clang-tools-extra/clangd/TUScheduler.h
+++ b/clang-tools-extra/clangd/TUScheduler.h
@@ -169,6 +169,11 @@ public:
 
   /// Called whenever the TU status is updated.
   virtual void onFileUpdated(PathRef File, const TUStatus &Status) {}
+
+  /// Preamble for the TU have changed. This might imply new semantics (e.g.
+  /// different highlightings). Any actions on the file are guranteed to see new
+  /// preamble after the callback.
+  virtual void onPreamblePublished(PathRef File) {}
 };
 
 /// Handles running tasks for ClangdServer and managing the resources (e.g.,