[clangd] Tracing improvements

Summary:
[clangd] Tracing improvements

Compose JSON using JSONExpr
Allow attaching metadata to spans (and avoid it if tracing is off)
Attach IDs and responses of JSON RPCs to their spans

The downside is that large responses make the trace viewer sluggish.
We should make our responses less huge :-) Or fix trace viewer.

Reviewers: ilya-biryukov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D40132

llvm-svn: 318928

1 files changed, 33 insertions, 20 deletions

diff --git a/clang-tools-extra/clangd/Trace.cpp b/clang-tools-extra/clangd/Trace.cpp
index 1607327ae73..6a51d0459f3 100644
--- a/clang-tools-extra/clangd/Trace.cpp
+++ b/clang-tools-extra/clangd/Trace.cpp
@@ -27,13 +27,17 @@ namespace {
 // Perhaps we should replace this by something that disturbs performance less.
 class Tracer {
 public:
-  Tracer(raw_ostream &Out)
-      : Out(Out), Sep(""), Start(std::chrono::system_clock::now()) {
+  Tracer(raw_ostream &Out, bool Pretty)
+      : Out(Out), Sep(""), Start(std::chrono::system_clock::now()),
+        JSONFormat(Pretty ? "{0:2}" : "{0}") {
     // The displayTimeUnit must be ns to avoid low-precision overlap
     // calculations!
     Out << R"({"displayTimeUnit":"ns","traceEvents":[)"
         << "\n";
-    rawEvent("M", R"("name": "process_name", "args":{"name":"clangd"})");
+    rawEvent("M", json::obj{
+                      {"name", "process_name"},
+                      {"args", json::obj{{"name", "clangd"}}},
+                  });
   }
 
   ~Tracer() {
@@ -43,7 +47,7 @@ public:
 
   // Record an event on the current thread. ph, pid, tid, ts are set.
   // Contents must be a list of the other JSON key/values.
-  template <typename T> void event(StringRef Phase, const T &Contents) {
+  void event(StringRef Phase, json::obj &&Contents) {
     uint64_t TID = get_threadid();
     std::lock_guard<std::mutex> Lock(Mu);
     // If we haven't already, emit metadata describing this thread.
@@ -51,24 +55,26 @@ public:
       SmallString<32> Name;
       get_thread_name(Name);
       if (!Name.empty()) {
-        rawEvent(
-            "M",
-            formatv(
-                R"("tid": {0}, "name": "thread_name", "args":{"name":"{1}"})",
-                TID, StringRef(&Name[0], Name.size())));
+        rawEvent("M", json::obj{
+                          {"tid", TID},
+                          {"name", "thread_name"},
+                          {"args", json::obj{{"name", Name}}},
+                      });
       }
     }
-    rawEvent(Phase, formatv(R"("ts":{0}, "tid":{1}, {2})", timestamp(), TID,
-                            Contents));
+    Contents["ts"] = timestamp();
+    Contents["tid"] = TID;
+    rawEvent(Phase, std::move(Contents));
   }
 
 private:
   // Record an event. ph and pid are set.
   // Contents must be a list of the other JSON key/values.
-  template <typename T>
-  void rawEvent(StringRef Phase, const T &Contents) /*REQUIRES(Mu)*/ {
+  void rawEvent(StringRef Phase, json::obj &&Event) /*REQUIRES(Mu)*/ {
     // PID 0 represents the clangd process.
-    Out << Sep << R"({"pid":0, "ph":")" << Phase << "\", " << Contents << "}";
+    Event["pid"] = 0;
+    Event["ph"] = Phase;
+    Out << Sep << formatv(JSONFormat, json::Expr(std::move(Event)));
     Sep = ",\n";
   }
 
@@ -82,14 +88,15 @@ private:
   const char *Sep /*GUARDED_BY(Mu)*/;
   DenseSet<uint64_t> ThreadsWithMD /*GUARDED_BY(Mu)*/;
   const sys::TimePoint<> Start;
+  const char *JSONFormat;
 };
 
 static Tracer *T = nullptr;
 } // namespace
 
-std::unique_ptr<Session> Session::create(raw_ostream &OS) {
+std::unique_ptr<Session> Session::create(raw_ostream &OS, bool Pretty) {
   assert(!T && "A session is already active");
-  T = new Tracer(OS);
+  T = new Tracer(OS, Pretty);
   return std::unique_ptr<Session>(new Session());
 }
 
@@ -101,19 +108,25 @@ Session::~Session() {
 void log(const Twine &Message) {
   if (!T)
     return;
-  T->event("i", formatv(R"("name":"{0}")", yaml::escape(Message.str())));
+  T->event("i", json::obj{
+                    {"name", "Log"},
+                    {"args", json::obj{{"Message", Message.str()}}},
+                });
 }
 
-Span::Span(const Twine &Text) {
+Span::Span(std::string Name) {
   if (!T)
     return;
-  T->event("B", formatv(R"("name":"{0}")", yaml::escape(Text.str())));
+  T->event("B", json::obj{{"name", std::move(Name)}});
+  Args = llvm::make_unique<json::obj>();
 }
 
 Span::~Span() {
   if (!T)
     return;
-  T->event("E", R"("_":0)" /* Dummy property to ensure valid JSON */);
+  if (!Args)
+    Args = llvm::make_unique<json::obj>();
+  T->event("E", Args ? json::obj{{"args", std::move(*Args)}} : json::obj{});
 }
 
 } // namespace trace