Use correct DefinitionKey length

Summary:
We need to provide the length of the final string, which is the same
as the length of the string before escaping, rather than the length of the
escaped string.
Also avoid recomputing the string by exposing the size directly.

Reviewed By: yoney

Differential Revision: D67982408

fbshipit-source-id: 3b671f6358748de2ecb29ee56bbfcfd7cbc0538d

thrift/compiler/generate/t_mstch_cpp2_generator.cc

@@ -913,8 +913,7 @@ class cpp_mstch_service : public mstch_service {
     return escape_binary_string(s.identify_definition(*service_));
   }
   mstch::node definition_key_length() {
-    schematizer s(*service_->program()->scope(), sm_, {});
-    return escape_binary_string(s.identify_definition(*service_)).length();
+    return schematizer::definition_identifier_length();
   }
 
  private:

thrift/compiler/sema/schematizer.cc

@@ -949,6 +949,10 @@ std::string_view schematizer::program_checksum(const t_program& program) {
           std::string(reinterpret_cast<const char*>(hash), sizeof(hash)));
 }
 
+size_t schematizer::definition_identifier_length() {
+  return 16;
+}
+
 std::string schematizer::identify_definition(const t_named& node) {
   // @lint-ignore CLANGTIDY facebook-hte-CArray
   unsigned char hash[SHA256_DIGEST_LENGTH];
@@ -958,8 +962,8 @@ std::string schematizer::identify_definition(const t_named& node) {
       node.program()->path(),
       node.name());
   SHA256(reinterpret_cast<const unsigned char*>(val.c_str()), val.size(), hash);
-  constexpr size_t num_bytes = 16;
-  return std::string(reinterpret_cast<const char*>(hash), num_bytes);
+  return std::string(
+      reinterpret_cast<const char*>(hash), definition_identifier_length());
 }
 
 int64_t schematizer::identify_program(const t_program& node) {

thrift/compiler/sema/schematizer.h

@@ -86,6 +86,7 @@ class schematizer {
   // across runs on different including programs.
   std::string identify_definition(const t_named& node);
   int64_t identify_program(const t_program& node);
+  static size_t definition_identifier_length();
 
   // Get the name of the program's schema const.
   static std::string name_schema(source_manager& sm, const t_program& node);

thrift/compiler/test/fixtures/service-schema/out/cpp2/gen-cpp2/PrimitivesService.cpp

@@ -23,7 +23,7 @@ apache::thrift::ServiceHandler<::cpp2::PrimitivesService>::CreateMethodMetadataR
 std::optional<apache::thrift::schema::DefinitionsSchema> apache::thrift::ServiceHandler<::cpp2::PrimitivesService>::getServiceSchema() {
   std::optional<apache::thrift::schema::DefinitionsSchema> ret = schema::DefinitionsSchema{};
   ret->schema = ::apache::thrift::SchemaRegistry::mergeSchemas(::cpp2::module_constants::_fbthrift_schema_b747839c13cb3aa5_includes());
-  ret->definitions = { {"\x0d\x05\x1d\xbc\xb2\xd5\x1d\x8f\x95\x45\xbb\x51\xfa\xcf\x0f\xfe", 64} };
+  ret->definitions = { {"\x0d\x05\x1d\xbc\xb2\xd5\x1d\x8f\x95\x45\xbb\x51\xfa\xcf\x0f\xfe", 16} };
   return ret;
 }
 #endif

thrift/compiler/test/fixtures/service-schema/out/cpp2_sinit/gen-cpp2/PrimitivesService.cpp

@@ -23,7 +23,7 @@ apache::thrift::ServiceHandler<::cpp2::PrimitivesService>::CreateMethodMetadataR
 std::optional<apache::thrift::schema::DefinitionsSchema> apache::thrift::ServiceHandler<::cpp2::PrimitivesService>::getServiceSchema() {
   std::optional<apache::thrift::schema::DefinitionsSchema> ret = schema::DefinitionsSchema{};
   ret->schema = ::apache::thrift::SchemaRegistry::mergeSchemas(::cpp2::module_constants::_fbthrift_schema_b747839c13cb3aa5_includes());
-  ret->definitions = { {"\x0d\x05\x1d\xbc\xb2\xd5\x1d\x8f\x95\x45\xbb\x51\xfa\xcf\x0f\xfe", 64} };
+  ret->definitions = { {"\x0d\x05\x1d\xbc\xb2\xd5\x1d\x8f\x95\x45\xbb\x51\xfa\xcf\x0f\xfe", 16} };
   return ret;
 }
 #endif