[C++] Add explicit keyword on generated constructors for Builder structs (#4452)

* Add explicit keyword on C++ generated constructors for Builder structs

* Add missing generated code for review

samples/monster_generated.h

@@ -314,7 +314,7 @@ struct MonsterBuilder {
   void add_equipped(flatbuffers::Offset<void> equipped) {
     fbb_.AddOffset(Monster::VT_EQUIPPED, equipped);
   }
-  MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -424,7 +424,7 @@ struct WeaponBuilder {
   void add_damage(int16_t damage) {
     fbb_.AddElement<int16_t>(Weapon::VT_DAMAGE, damage, 0);
   }
-  WeaponBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit WeaponBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }

src/idl_gen_cpp.cpp

@@ -1693,7 +1693,7 @@ class CppGenerator : public BaseGenerator {
     }
 
     // Builder constructor
-    code_ += "  {{STRUCT_NAME}}Builder(flatbuffers::FlatBufferBuilder &_fbb)";
+    code_ += "  explicit {{STRUCT_NAME}}Builder(flatbuffers::FlatBufferBuilder &_fbb)";
     code_ += "        : fbb_(_fbb) {";
     code_ += "    start_ = fbb_.StartTable();";
     code_ += "  }";

tests/monster_test_generated.h

@@ -353,7 +353,7 @@ struct InParentNamespace FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
 struct InParentNamespaceBuilder {
   flatbuffers::FlatBufferBuilder &fbb_;
   flatbuffers::uoffset_t start_;
-  InParentNamespaceBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit InParentNamespaceBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -395,7 +395,7 @@ struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
 struct MonsterBuilder {
   flatbuffers::FlatBufferBuilder &fbb_;
   flatbuffers::uoffset_t start_;
-  MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -454,7 +454,7 @@ struct TestSimpleTableWithEnumBuilder {
   void add_color(Color color) {
     fbb_.AddElement<int8_t>(TestSimpleTableWithEnum::VT_COLOR, static_cast<int8_t>(color), 2);
   }
-  TestSimpleTableWithEnumBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit TestSimpleTableWithEnumBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -537,7 +537,7 @@ struct StatBuilder {
   void add_count(uint16_t count) {
     fbb_.AddElement<uint16_t>(Stat::VT_COUNT, count, 0);
   }
-  StatBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit StatBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -1078,7 +1078,7 @@ struct MonsterBuilder {
   void add_parent_namespace_test(flatbuffers::Offset<MyGame::InParentNamespace> parent_namespace_test) {
     fbb_.AddOffset(Monster::VT_PARENT_NAMESPACE_TEST, parent_namespace_test);
   }
-  MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -1419,7 +1419,7 @@ struct TypeAliasesBuilder {
   void add_vf64(flatbuffers::Offset<flatbuffers::Vector<double>> vf64) {
     fbb_.AddOffset(TypeAliases::VT_VF64, vf64);
   }
-  TypeAliasesBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit TypeAliasesBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }

tests/namespace_test/namespace_test1_generated.h

@@ -99,7 +99,7 @@ struct TableInNestedNSBuilder {
   void add_foo(int32_t foo) {
     fbb_.AddElement<int32_t>(TableInNestedNS::VT_FOO, foo, 0);
   }
-  TableInNestedNSBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit TableInNestedNSBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }

tests/namespace_test/namespace_test2_generated.h

@@ -70,7 +70,7 @@ struct TableInFirstNSBuilder {
   void add_foo_struct(const NamespaceA::NamespaceB::StructInNestedNS *foo_struct) {
     fbb_.AddStruct(TableInFirstNS::VT_FOO_STRUCT, foo_struct);
   }
-  TableInFirstNSBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit TableInFirstNSBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -134,7 +134,7 @@ struct TableInCBuilder {
   void add_refer_to_a2(flatbuffers::Offset<NamespaceA::SecondTableInA> refer_to_a2) {
     fbb_.AddOffset(TableInC::VT_REFER_TO_A2, refer_to_a2);
   }
-  TableInCBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit TableInCBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -184,7 +184,7 @@ struct SecondTableInABuilder {
   void add_refer_to_c(flatbuffers::Offset<NamespaceC::TableInC> refer_to_c) {
     fbb_.AddOffset(SecondTableInA::VT_REFER_TO_C, refer_to_c);
   }
-  SecondTableInABuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit SecondTableInABuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }

tests/namespace_test/namespace_test2_generated.ts

 // automatically generated by the FlatBuffers compiler, do not modify
 
-import * as NS4989953370203581498 from "./namespace_test1_generated";
+import * as NS9459827973991502386 from "./namespace_test1_generated";
 /**
  * @constructor
  */
@@ -39,24 +39,24 @@ static getRootAsTableInFirstNS(bb:flatbuffers.ByteBuffer, obj?:TableInFirstNS):T
  * @param {NamespaceA.NamespaceB.TableInNestedNS=} obj
  * @returns {NamespaceA.NamespaceB.TableInNestedNS|null}
  */
-fooTable(obj?:NS4989953370203581498.NamespaceA.NamespaceB.TableInNestedNS):NS4989953370203581498.NamespaceA.NamespaceB.TableInNestedNS|null {
+fooTable(obj?:NS9459827973991502386.NamespaceA.NamespaceB.TableInNestedNS):NS9459827973991502386.NamespaceA.NamespaceB.TableInNestedNS|null {
   var offset = this.bb.__offset(this.bb_pos, 4);
-  return offset ? (obj || new NS4989953370203581498.NamespaceA.NamespaceB.TableInNestedNS).__init(this.bb.__indirect(this.bb_pos + offset), this.bb) : null;
+  return offset ? (obj || new NS9459827973991502386.NamespaceA.NamespaceB.TableInNestedNS).__init(this.bb.__indirect(this.bb_pos + offset), this.bb) : null;
 };
 
 /**
  * @returns {NamespaceA.NamespaceB.EnumInNestedNS}
  */
-fooEnum():NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS {
+fooEnum():NS9459827973991502386.NamespaceA.NamespaceB.EnumInNestedNS {
   var offset = this.bb.__offset(this.bb_pos, 6);
-  return offset ? /** @type {NamespaceA.NamespaceB.EnumInNestedNS} */ (this.bb.readInt8(this.bb_pos + offset)) : NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS.A;
+  return offset ? /** @type {NamespaceA.NamespaceB.EnumInNestedNS} */ (this.bb.readInt8(this.bb_pos + offset)) : NS9459827973991502386.NamespaceA.NamespaceB.EnumInNestedNS.A;
 };
 
 /**
  * @param {NamespaceA.NamespaceB.EnumInNestedNS} value
  * @returns {boolean}
  */
-mutate_foo_enum(value:NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS):boolean {
+mutate_foo_enum(value:NS9459827973991502386.NamespaceA.NamespaceB.EnumInNestedNS):boolean {
   var offset = this.bb.__offset(this.bb_pos, 6);
 
   if (offset === 0) {
@@ -71,9 +71,9 @@ mutate_foo_enum(value:NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS
  * @param {NamespaceA.NamespaceB.StructInNestedNS=} obj
  * @returns {NamespaceA.NamespaceB.StructInNestedNS|null}
  */
-fooStruct(obj?:NS4989953370203581498.NamespaceA.NamespaceB.StructInNestedNS):NS4989953370203581498.NamespaceA.NamespaceB.StructInNestedNS|null {
+fooStruct(obj?:NS9459827973991502386.NamespaceA.NamespaceB.StructInNestedNS):NS9459827973991502386.NamespaceA.NamespaceB.StructInNestedNS|null {
   var offset = this.bb.__offset(this.bb_pos, 8);
-  return offset ? (obj || new NS4989953370203581498.NamespaceA.NamespaceB.StructInNestedNS).__init(this.bb_pos + offset, this.bb) : null;
+  return offset ? (obj || new NS9459827973991502386.NamespaceA.NamespaceB.StructInNestedNS).__init(this.bb_pos + offset, this.bb) : null;
 };
 
 /**
@@ -95,8 +95,8 @@ static addFooTable(builder:flatbuffers.Builder, fooTableOffset:flatbuffers.Offse
  * @param {flatbuffers.Builder} builder
  * @param {NamespaceA.NamespaceB.EnumInNestedNS} fooEnum
  */
-static addFooEnum(builder:flatbuffers.Builder, fooEnum:NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS) {
-  builder.addFieldInt8(1, fooEnum, NS4989953370203581498.NamespaceA.NamespaceB.EnumInNestedNS.A);
+static addFooEnum(builder:flatbuffers.Builder, fooEnum:NS9459827973991502386.NamespaceA.NamespaceB.EnumInNestedNS) {
+  builder.addFieldInt8(1, fooEnum, NS9459827973991502386.NamespaceA.NamespaceB.EnumInNestedNS.A);
 };
 
 /**

tests/union_vector/union_vector_generated.h

@@ -214,7 +214,7 @@ struct AttackerBuilder {
   void add_sword_attack_damage(int32_t sword_attack_damage) {
     fbb_.AddElement<int32_t>(Attacker::VT_SWORD_ATTACK_DAMAGE, sword_attack_damage, 0);
   }
-  AttackerBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit AttackerBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
@@ -327,7 +327,7 @@ struct MovieBuilder {
   void add_characters(flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<void>>> characters) {
     fbb_.AddOffset(Movie::VT_CHARACTERS, characters);
   }
-  MovieBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  explicit MovieBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }