[clangd][xpc] pass the LSP value using data instead of string

[arphaman]

Summary

Use XPC's data type instead of string to pass the LSP value from Clangd. This will make it easier to use from sourcekit-lsp (https://github.com/apple/sourcekit-lsp/pull/112), where I will be able to drop a conversion between Data and String.

[arphaman]

Added missing xpc_release in the test.

[jkorous]

I'd add a test with non-empty non-LSP dictionary to specifically test that we're ignoring the content. I like const-correctness but that's up to you. Otherwise LGTM.

clang-tools-extra/clangd/unittests/xpc/ConversionTests.cpp

34

We should also test something like

const char* key = "NotAnLSP";
const char* value = "Foo";
xpc_object_t EmptyDict = xpc_dictionary_create(&key, &value, 1);

clang-tools-extra/clangd/xpc/Conversion.cpp

22–23

Nit - const std::string?

29–36

Nit -const size_t and const char * const?

clang-tools-extra/clangd/unittests/xpc/ConversionTests.cpp

for (auto &testcase :
         json::Value("123"), json::Value(" "),
         json::Value{true, "foo", nullptr, 42},
         json::Value(json::Object{
             {"a", true}, {"b", "foo"}, {"c", nullptr}, {"d", 42}})}) {
     EXPECT_TRUE(testcase == xpcToJson(jsonToXpc(testcase))) << testcase;
   }
 }
 
+TEST(JsonXpcConversionTest, IgnoreNonLSPDictionary) {
+  xpc_object_t EmptyDict = xpc_dictionary_create(nullptr, nullptr, 0);
+  json::Value Val = xpcToJson(EmptyDict);
+  ASSERT_EQ(Val.kind(), json::Value::Null);
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/xpc/Conversion.cpp

 #include <vector>
 
 using namespace llvm;
 namespace clang {
 namespace clangd {
 
 xpc_object_t jsonToXpc(const json::Value &JSON) {
   const char *const Key = "LSP";
-  xpc_object_t PayloadObj = xpc_string_create(llvm::to_string(JSON).c_str());
+  std::string Str = llvm::to_string(JSON);
+  xpc_object_t PayloadObj = xpc_data_create(Str.data(), Str.size());
   return xpc_dictionary_create(&Key, &PayloadObj, 1);
 }
 
 json::Value xpcToJson(const xpc_object_t &XPCObject) {
   if (xpc_get_type(XPCObject) == XPC_TYPE_DICTIONARY) {
-    const char *const LSP = xpc_dictionary_get_string(XPCObject, "LSP");
-    auto Json = json::parse(llvm::StringRef(LSP));
+    size_t Length;
+    const char *LSP =
+        (const char *)xpc_dictionary_get_data(XPCObject, "LSP", &Length);
+    if (!LSP) {
+      elog("ignoring non-LSP XPC message");
+      return json::Value(nullptr);
+    }
+    auto Json = json::parse(llvm::StringRef(LSP, Length));
     if (Json)
       return *Json;
     else
       elog("JSON parse error: {0}", toString(Json.takeError()));
   }
   return json::Value(nullptr);
 }
 
 } // namespace clangd
 } // namespace clang