[clangd] Make version in PublishDiagnosticsParams optional

[kadircet]

Summary

We were serializing it no matter what, which was against the spec

[sammccall]

clang-tools-extra/clangd/Protocol.cpp

569

nit: I'm not sure it's actually worth having these comments everywhere. The move is harmless apart from readability, and the readability of drawing attention to them seems worse.

clang-tools-extra/clangd/Protocol.cpp

bool fromJSON(const llvm::json::Value &Params, Diagnostic &R) {
   O.map("severity", R.severity);
   O.map("category", R.category);
   O.map("code", R.code);
   O.map("source", R.source);
   return true;
 }
 
 llvm::json::Value toJSON(const PublishDiagnosticsParams &PDP) {
-  return llvm::json::Object{
+  llvm::json::Object Result{
       {"uri", PDP.uri},
       {"diagnostics", PDP.diagnostics},
-      {"version", PDP.version},
   };
+  if (PDP.version)
+    Result["version"] = PDP.version;
+  return std::move(Result);
 }
 
 bool fromJSON(const llvm::json::Value &Params, CodeActionContext &R) {
   llvm::json::ObjectMapper O(Params);
   return O && O.map("diagnostics", R.diagnostics);
 }
 
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Diagnostic &D) {

clang-tools-extra/clangd/test/diagnostics-no-tidy.test

 # CHECK-NEXT:  }
 ---
 {"jsonrpc":"2.0","id":2,"method":"sync","params":null}
 ---
 {"jsonrpc":"2.0","method":"textDocument/didClose","params":{"textDocument":{"uri":"test:///foo.c"}}}
 #      CHECK:  "method": "textDocument/publishDiagnostics",
 # CHECK-NEXT:  "params": {
 # CHECK-NEXT:    "diagnostics": [],
-# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c",
-# CHECK-NEXT:    "version": null
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
 # CHECK-NEXT:  }
 ---
 {"jsonrpc":"2.0","id":5,"method":"shutdown"}
 ---
 {"jsonrpc":"2.0","method":"exit"}

clang-tools-extra/clangd/test/diagnostics.test

 # CHECK-NEXT:  }
 ---
 {"jsonrpc":"2.0","id":2,"method":"sync","params":null}
 ---
 {"jsonrpc":"2.0","method":"textDocument/didClose","params":{"textDocument":{"uri":"test:///foo.c"}}}
 #      CHECK:  "method": "textDocument/publishDiagnostics",
 # CHECK-NEXT:  "params": {
 # CHECK-NEXT:    "diagnostics": [],
-# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c",
-# CHECK-NEXT:    "version": null
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
 # CHECK-NEXT:  }
 ---
 {"jsonrpc":"2.0","id":5,"method":"shutdown"}
 ---
 {"jsonrpc":"2.0","method":"exit"}