C++: mini_reflect: Add DefaultTypeTable (#4614)

* mini_reflect: Add DefaultTypeTable

Currently it's very easy to make a mistake when it comes to
instantiating the TypeTable to print a buffer because it is not type
safe.

This will allow us to write safer cpp code:

flatbuffers::FlatBufferToString(reinterpret_cast<const uint8_t *>(&t),
                                decltype(t)::DefaultTypeTable());

* c++: mini_reflect: update generated code

* Ensure types and names are set for mini_reflect

* c++: mini_refelct: update unit tests with new typed TypeTable

* Adding PR feedback of sylte and naming convention

7 files changed, 119 insertions, 68 deletions

diff --git a/samples/monster_generated.h b/samples/monster_generated.h
index baf3fe74..32d44d00 100644
--- a/samples/monster_generated.h
+++ b/samples/monster_generated.h
@@ -17,6 +17,12 @@ struct MonsterT;
 struct Weapon;
 struct WeaponT;
 
+inline flatbuffers::TypeTable *Vec3TypeTable();
+
+inline flatbuffers::TypeTable *MonsterTypeTable();
+
+inline flatbuffers::TypeTable *WeaponTypeTable();
+
 enum Color {
   Color_Red = 0,
   Color_Green = 1,
@@ -185,6 +191,9 @@ struct MonsterT : public flatbuffers::NativeTable {
 
 struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef MonsterT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return MonsterTypeTable();
+  }
   enum {
     VT_POS = 4,
     VT_MANA = 6,
@@ -384,6 +393,9 @@ struct WeaponT : public flatbuffers::NativeTable {
 
 struct Weapon FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef WeaponT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return WeaponTypeTable();
+  }
   enum {
     VT_NAME = 4,
     VT_DAMAGE = 6
@@ -603,12 +615,6 @@ inline void EquipmentUnion::Reset() {
   type = Equipment_NONE;
 }
 
-inline flatbuffers::TypeTable *Vec3TypeTable();
-
-inline flatbuffers::TypeTable *MonsterTypeTable();
-
-inline flatbuffers::TypeTable *WeaponTypeTable();
-
 inline flatbuffers::TypeTable *ColorTypeTable() {
   static flatbuffers::TypeCode type_codes[] = {
     { flatbuffers::ET_CHAR, 0, 0 },
diff --git a/src/idl_gen_cpp.cpp b/src/idl_gen_cpp.cpp
index 15f2f38c..ea01bf1c 100644
--- a/src/idl_gen_cpp.cpp
+++ b/src/idl_gen_cpp.cpp
@@ -231,6 +231,18 @@ class CppGenerator : public BaseGenerator {
         code_ += "";
       }
     }
+    // Generate preablmle code for mini reflection.
+    if (parser_.opts.mini_reflect != IDLOptions::kNone) {
+      // To break cyclic dependencies, first pre-declare all tables/structs.
+      for (auto it = parser_.structs_.vec.begin();
+           it != parser_.structs_.vec.end(); ++it) {
+        const auto &struct_def = **it;
+        if (!struct_def.generated) {
+          SetNameSpace(struct_def.defined_namespace);
+          GenMiniReflectPre(&struct_def);
+        }
+      }
+    }
 
     // Generate code for all the enum declarations.
     for (auto it = parser_.enums_.vec.begin(); it != parser_.enums_.vec.end();
@@ -280,15 +292,6 @@ class CppGenerator : public BaseGenerator {
 
     // Generate code for mini reflection.
     if (parser_.opts.mini_reflect != IDLOptions::kNone) {
-      // To break cyclic dependencies, first pre-declare all tables/structs.
-      for (auto it = parser_.structs_.vec.begin();
-           it != parser_.structs_.vec.end(); ++it) {
-        const auto &struct_def = **it;
-        if (!struct_def.generated) {
-          SetNameSpace(struct_def.defined_namespace);
-          GenMiniReflectPre(&struct_def);
-        }
-      }
       // Then the unions/enums that may refer to them.
       for (auto it = parser_.enums_.vec.begin(); it != parser_.enums_.vec.end();
            ++it) {
@@ -1503,6 +1506,12 @@ class CppGenerator : public BaseGenerator {
     if (parser_.opts.generate_object_based_api) {
       code_ += "  typedef {{NATIVE_NAME}} NativeTableType;";
     }
+    if (parser_.opts.mini_reflect != IDLOptions::kNone) {
+      code_ += "  static flatbuffers::TypeTable *MiniReflectTypeTable() {";
+      code_ += "    return {{STRUCT_NAME}}TypeTable();";
+      code_ += "  }";
+    }
+
 
     GenFullyQualifiedNameGetter(struct_def, Name(struct_def));
 
diff --git a/tests/monster_test_generated.h b/tests/monster_test_generated.h
index d2a0d505..07813839 100644
--- a/tests/monster_test_generated.h
+++ b/tests/monster_test_generated.h
@@ -39,6 +39,32 @@ struct MonsterT;
 struct TypeAliases;
 struct TypeAliasesT;
 
+}  // namespace Example
+
+inline flatbuffers::TypeTable *InParentNamespaceTypeTable();
+
+namespace Example2 {
+
+inline flatbuffers::TypeTable *MonsterTypeTable();
+
+}  // namespace Example2
+
+namespace Example {
+
+inline flatbuffers::TypeTable *TestTypeTable();
+
+inline flatbuffers::TypeTable *TestSimpleTableWithEnumTypeTable();
+
+inline flatbuffers::TypeTable *Vec3TypeTable();
+
+inline flatbuffers::TypeTable *AbilityTypeTable();
+
+inline flatbuffers::TypeTable *StatTypeTable();
+
+inline flatbuffers::TypeTable *MonsterTypeTable();
+
+inline flatbuffers::TypeTable *TypeAliasesTypeTable();
+
 enum Color {
   Color_Red = 1,
   Color_Green = 2,
@@ -332,6 +358,9 @@ struct InParentNamespaceT : public flatbuffers::NativeTable {
 
 struct InParentNamespace FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef InParentNamespaceT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return InParentNamespaceTypeTable();
+  }
   bool Verify(flatbuffers::Verifier &verifier) const {
     return VerifyTableStart(verifier) &&
            verifier.EndTable();
@@ -374,6 +403,9 @@ struct MonsterT : public flatbuffers::NativeTable {
 
 struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef MonsterT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return MonsterTypeTable();
+  }
   bool Verify(flatbuffers::Verifier &verifier) const {
     return VerifyTableStart(verifier) &&
            verifier.EndTable();
@@ -420,6 +452,9 @@ struct TestSimpleTableWithEnumT : public flatbuffers::NativeTable {
 
 struct TestSimpleTableWithEnum FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef TestSimpleTableWithEnumT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return TestSimpleTableWithEnumTypeTable();
+  }
   enum {
     VT_COLOR = 4
   };
@@ -480,6 +515,9 @@ struct StatT : public flatbuffers::NativeTable {
 
 struct Stat FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef StatT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return StatTypeTable();
+  }
   enum {
     VT_ID = 4,
     VT_VAL = 6,
@@ -623,6 +661,9 @@ struct MonsterT : public flatbuffers::NativeTable {
 /// an example documentation comment: monster object
 struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef MonsterT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return MonsterTypeTable();
+  }
   enum {
     VT_POS = 4,
     VT_MANA = 6,
@@ -1261,6 +1302,9 @@ struct TypeAliasesT : public flatbuffers::NativeTable {
 
 struct TypeAliases FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef TypeAliasesT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return TypeAliasesTypeTable();
+  }
   enum {
     VT_I8 = 4,
     VT_U8 = 6,
@@ -1890,32 +1934,6 @@ inline void AnyUnion::Reset() {
   type = Any_NONE;
 }
 
-}  // namespace Example
-
-inline flatbuffers::TypeTable *InParentNamespaceTypeTable();
-
-namespace Example2 {
-
-inline flatbuffers::TypeTable *MonsterTypeTable();
-
-}  // namespace Example2
-
-namespace Example {
-
-inline flatbuffers::TypeTable *TestTypeTable();
-
-inline flatbuffers::TypeTable *TestSimpleTableWithEnumTypeTable();
-
-inline flatbuffers::TypeTable *Vec3TypeTable();
-
-inline flatbuffers::TypeTable *AbilityTypeTable();
-
-inline flatbuffers::TypeTable *StatTypeTable();
-
-inline flatbuffers::TypeTable *MonsterTypeTable();
-
-inline flatbuffers::TypeTable *TypeAliasesTypeTable();
-
 inline flatbuffers::TypeTable *ColorTypeTable() {
   static flatbuffers::TypeCode type_codes[] = {
     { flatbuffers::ET_CHAR, 0, 0 },
diff --git a/tests/namespace_test/namespace_test1_generated.h b/tests/namespace_test/namespace_test1_generated.h
index 47e6a262..4b85249a 100644
--- a/tests/namespace_test/namespace_test1_generated.h
+++ b/tests/namespace_test/namespace_test1_generated.h
@@ -13,6 +13,10 @@ struct TableInNestedNS;
 
 struct StructInNestedNS;
 
+inline flatbuffers::TypeTable *TableInNestedNSTypeTable();
+
+inline flatbuffers::TypeTable *StructInNestedNSTypeTable();
+
 enum EnumInNestedNS {
   EnumInNestedNS_A = 0,
   EnumInNestedNS_B = 1,
@@ -74,6 +78,9 @@ MANUALLY_ALIGNED_STRUCT(4) StructInNestedNS FLATBUFFERS_FINAL_CLASS {
 STRUCT_END(StructInNestedNS, 8);
 
 struct TableInNestedNS FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return TableInNestedNSTypeTable();
+  }
   enum {
     VT_FOO = 4
   };
@@ -116,10 +123,6 @@ inline flatbuffers::Offset<TableInNestedNS> CreateTableInNestedNS(
   return builder_.Finish();
 }
 
-inline flatbuffers::TypeTable *TableInNestedNSTypeTable();
-
-inline flatbuffers::TypeTable *StructInNestedNSTypeTable();
-
 inline flatbuffers::TypeTable *EnumInNestedNSTypeTable() {
   static flatbuffers::TypeCode type_codes[] = {
     { flatbuffers::ET_CHAR, 0, 0 },
diff --git a/tests/namespace_test/namespace_test2_generated.h b/tests/namespace_test/namespace_test2_generated.h
index a8818146..510e1de3 100644
--- a/tests/namespace_test/namespace_test2_generated.h
+++ b/tests/namespace_test/namespace_test2_generated.h
@@ -24,7 +24,24 @@ namespace NamespaceA {
 
 struct SecondTableInA;
 
+inline flatbuffers::TypeTable *TableInFirstNSTypeTable();
+
+}  // namespace NamespaceA
+
+namespace NamespaceC {
+
+inline flatbuffers::TypeTable *TableInCTypeTable();
+
+}  // namespace NamespaceC
+
+namespace NamespaceA {
+
+inline flatbuffers::TypeTable *SecondTableInATypeTable();
+
 struct TableInFirstNS FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return TableInFirstNSTypeTable();
+  }
   enum {
     VT_FOO_TABLE = 4,
     VT_FOO_ENUM = 6,
@@ -99,6 +116,9 @@ inline flatbuffers::Offset<TableInFirstNS> CreateTableInFirstNS(
 namespace NamespaceC {
 
 struct TableInC FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return TableInCTypeTable();
+  }
   enum {
     VT_REFER_TO_A1 = 4,
     VT_REFER_TO_A2 = 6
@@ -161,6 +181,9 @@ inline flatbuffers::Offset<TableInC> CreateTableInC(
 namespace NamespaceA {
 
 struct SecondTableInA FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return SecondTableInATypeTable();
+  }
   enum {
     VT_REFER_TO_C = 4
   };
@@ -212,20 +235,6 @@ namespace NamespaceC {
 
 namespace NamespaceA {
 
-inline flatbuffers::TypeTable *TableInFirstNSTypeTable();
-
-}  // namespace NamespaceA
-
-namespace NamespaceC {
-
-inline flatbuffers::TypeTable *TableInCTypeTable();
-
-}  // namespace NamespaceC
-
-namespace NamespaceA {
-
-inline flatbuffers::TypeTable *SecondTableInATypeTable();
-
 inline flatbuffers::TypeTable *TableInFirstNSTypeTable() {
   static flatbuffers::TypeCode type_codes[] = {
     { flatbuffers::ET_SEQUENCE, 0, 0 },
diff --git a/tests/test.cpp b/tests/test.cpp
index 0dea810c..a89e56dd 100644
--- a/tests/test.cpp
+++ b/tests/test.cpp
@@ -819,7 +819,7 @@ void ReflectionTest(uint8_t *flatbuf, size_t length) {
 }
 
 void MiniReflectFlatBuffersTest(uint8_t *flatbuf) {
-  auto s = flatbuffers::FlatBufferToString(flatbuf, MonsterTypeTable());
+  auto s = flatbuffers::FlatBufferToString(flatbuf, Monster::MiniReflectTypeTable());
   TEST_EQ_STR(
       s.c_str(),
       "{ "
diff --git a/tests/union_vector/union_vector_generated.h b/tests/union_vector/union_vector_generated.h
index 14c3cc91..77de579e 100644
--- a/tests/union_vector/union_vector_generated.h
+++ b/tests/union_vector/union_vector_generated.h
@@ -16,6 +16,14 @@ struct BookReader;
 struct Movie;
 struct MovieT;
 
+inline flatbuffers::TypeTable *AttackerTypeTable();
+
+inline flatbuffers::TypeTable *RapunzelTypeTable();
+
+inline flatbuffers::TypeTable *BookReaderTypeTable();
+
+inline flatbuffers::TypeTable *MovieTypeTable();
+
 enum Character {
   Character_NONE = 0,
   Character_MuLan = 1,
@@ -183,6 +191,9 @@ struct AttackerT : public flatbuffers::NativeTable {
 
 struct Attacker FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef AttackerT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return AttackerTypeTable();
+  }
   enum {
     VT_SWORD_ATTACK_DAMAGE = 4
   };
@@ -240,6 +251,9 @@ struct MovieT : public flatbuffers::NativeTable {
 
 struct Movie FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   typedef MovieT NativeTableType;
+  static flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return MovieTypeTable();
+  }
   enum {
     VT_MAIN_CHARACTER_TYPE = 4,
     VT_MAIN_CHARACTER = 6,
@@ -595,14 +609,6 @@ inline void CharacterUnion::Reset() {
   type = Character_NONE;
 }
 
-inline flatbuffers::TypeTable *AttackerTypeTable();
-
-inline flatbuffers::TypeTable *RapunzelTypeTable();
-
-inline flatbuffers::TypeTable *BookReaderTypeTable();
-
-inline flatbuffers::TypeTable *MovieTypeTable();
-
 inline flatbuffers::TypeTable *CharacterTypeTable() {
   static flatbuffers::TypeCode type_codes[] = {
     { flatbuffers::ET_SEQUENCE, 0, -1 },