[C++] Adds basic schema evolution tests (#5611)

* Added basic schema evolution tests

* Add BUILD targets for evolution tests. Added to test/generate_code scripts

* Use vector.front() instead of vector.data()

* Added --scoped-enums option for evolution test

BUILD

@@ -139,6 +139,8 @@ cc_test(
         "src/idl_parser.cpp",
         "src/reflection.cpp",
         "src/util.cpp",
+        "tests/evolution_test/evolution_v1_generated.h",
+        "tests/evolution_test/evolution_v2_generated.h",
         "tests/namespace_test/namespace_test1_generated.h",
         "tests/namespace_test/namespace_test2_generated.h",
         "tests/native_type_test_impl.cpp",
@@ -159,6 +161,10 @@ cc_test(
         ":tests/arrays_test.bfbs",
         ":tests/arrays_test.fbs",
         ":tests/arrays_test.golden",
+        ":tests/evolution_test/evolution_v1.fbs",
+        ":tests/evolution_test/evolution_v1.json",
+        ":tests/evolution_test/evolution_v2.fbs",
+        ":tests/evolution_test/evolution_v2.json",
         ":tests/include_test/include_test1.fbs",
         ":tests/include_test/sub/include_test2.fbs",
         ":tests/monster_extra.fbs",

tests/evolution_test/evolution_v1.fbs

+namespace Evolution.V1;
+
+table TableA {
+    a:float;
+    b:int;
+}
+
+table TableB {
+    a:int;
+}
+
+enum Enum : byte {
+    King,
+    Queen
+}
+
+union Union {
+    TableA,
+    TableB
+}
+
+struct Struct {
+    a:int;
+    b:double;
+}
+
+table Root {
+    a:int;
+    b:bool;
+    c:Union;
+    d:Enum;
+    e:TableA;
+    f:Struct;
+    g:[int];
+    h:[TableB];
+    i:int = 1234;
+}
+
+root_type Root;
\ No newline at end of file

tests/evolution_test/evolution_v1.json

+{
+  "a": 42,
+  "b": true,
+  "c_type": "TableB",
+  "c": {
+    "a": 15
+  },
+  "d": "King",
+  "e": {
+    "a": 3.1452,
+    "b": 325
+  },
+  "f":{
+    "a": 16,
+    "b": 243.980943
+  },
+  "g": [ 7, 8, 9],
+  "h": [
+    {
+      "a": 212
+    },
+    {
+      "a": 459
+    }
+  ]
+}
\ No newline at end of file

tests/evolution_test/evolution_v2.fbs

+namespace Evolution.V2;
+
+table TableA {
+    b:int (id: 1);      // swapped with 'a'
+    a:float (id: 0);    // swapped with 'b'
+    c:string (id: 2);   // new in v2
+}
+
+table TableB {
+    a:int;
+}
+
+table TableC {          // new in v2
+    a:double;
+    b:string;
+}
+
+enum Enum : byte {
+    King,
+    Queen,
+    Rook,               // new in v2
+    Bishop              // new in v2
+}
+
+union Union {
+    TableA,
+    TableB,
+    TableC
+}
+
+struct Struct {
+    a:int;
+    b:double;
+}
+
+table Root {
+    a:int (deprecated); // deprecated in v2
+    b:bool;
+    c:Union;
+    d:Enum;
+    e:TableA;
+    ff:Struct;          // renamed from 'f' in v1
+    g:[int];
+    h:[TableB];
+    i:uint = 1234;
+    j:TableC;           // new in v2
+    k:uint8 = 56;       // new in v2
+}
+
+root_type Root;
\ No newline at end of file

tests/evolution_test/evolution_v2.json

+{
+  "b": false,
+  "c_type": "TableC",
+  "c": {
+    "a": 984.2494
+  },
+  "d": "Bishop",
+  "e": {
+    "a": 3.1452,
+    "b": 435,
+    "c": "yummy yummy fig bar bar"
+  },
+  "ff":{
+    "a": 35,
+    "b": 243.980943
+  },
+  "g": [ 7, 8, 10],
+  "h": [
+    {
+      "a": 212
+    },
+    {
+      "a": 459
+    },
+    {
+      "a": 333
+    }
+  ],
+  "i": 4321,
+  "j": {
+    "a": 9874.342,
+    "b": "more please"
+  }
+}

tests/generate_code.bat

@@ -18,6 +18,7 @@ if "%1"=="-b" set buildtype=%2
 ..\%buildtype%\flatc.exe --cpp --java --csharp --dart --go --binary --lobster --lua --python --js --ts --php --rust --grpc --gen-mutable --reflect-names --gen-object-api --gen-compare --no-includes --cpp-ptr-type flatbuffers::unique_ptr  --no-fb-import -I include_test monster_test.fbs monsterdata_test.json || goto FAIL
 ..\%buildtype%\flatc.exe --cpp --java --csharp --dart --go --binary --lobster --lua --python --js --ts --php --rust --gen-mutable --reflect-names --no-fb-import --cpp-ptr-type flatbuffers::unique_ptr  -o namespace_test namespace_test/namespace_test1.fbs namespace_test/namespace_test2.fbs || goto FAIL
 ..\%buildtype%\flatc.exe --cpp --java --csharp --js --ts --php --gen-mutable --reflect-names --gen-object-api --gen-compare --cpp-ptr-type flatbuffers::unique_ptr -o union_vector ./union_vector/union_vector.fbs || goto FAIL
+..\%buildtype%\flatc.exe --cpp --scoped-enums -o evolution_test ./evolution_test/evolution_v1.fbs ./evolution_test/evolution_v2.fbs|| goto FAIL
 ..\%buildtype%\flatc.exe -b --schema --bfbs-comments --bfbs-builtins -I include_test monster_test.fbs || goto FAIL
 ..\%buildtype%\flatc.exe -b --schema --bfbs-comments --bfbs-builtins -I include_test arrays_test.fbs || goto FAIL
 ..\%buildtype%\flatc.exe --jsonschema --schema -I include_test monster_test.fbs || goto FAIL

tests/generate_code.sh

@@ -18,6 +18,7 @@ set -e
 ../flatc --cpp --java --kotlin  --csharp --dart --go --binary --lobster --lua --python --js --ts --php --rust --grpc --gen-mutable --reflect-names --gen-object-api --gen-compare --no-includes --cpp-ptr-type flatbuffers::unique_ptr  --no-fb-import -I include_test monster_test.fbs monsterdata_test.json
 ../flatc --cpp --java --kotlin --csharp --dart --go --binary --lobster --lua --python --js --ts --php --rust --gen-mutable --reflect-names --no-fb-import --cpp-ptr-type flatbuffers::unique_ptr  -o namespace_test namespace_test/namespace_test1.fbs namespace_test/namespace_test2.fbs
 ../flatc --cpp --java --kotlin --csharp --js --ts --php --gen-mutable --reflect-names --gen-object-api --gen-compare --cpp-ptr-type flatbuffers::unique_ptr -o union_vector ./union_vector/union_vector.fbs
+../flatc --cpp --scoped-enums -o evolution_test ./evolution_test/evolution_v*.fbs
 ../flatc -b --schema --bfbs-comments --bfbs-builtins -I include_test monster_test.fbs
 ../flatc -b --schema --bfbs-comments --bfbs-builtins -I include_test arrays_test.fbs
 ../flatc --jsonschema --schema -I include_test monster_test.fbs

tests/test.cpp

@@ -37,6 +37,8 @@
 #include "monster_extra_generated.h"
 #if !defined(_MSC_VER) || _MSC_VER >= 1700
 #  include "arrays_test_generated.h"
+#  include "evolution_test/evolution_v1_generated.h"
+#  include "evolution_test/evolution_v2_generated.h"
 #endif
 
 #include "native_type_test_generated.h"
@@ -2310,6 +2312,76 @@ void InvalidNestedFlatbufferTest() {
           false);
 }
 
+void EvolutionTest() {
+  // VS10 does not support typed enums, exclude from tests
+#if !defined(_MSC_VER) || _MSC_VER >= 1700
+    const int NUM_VERSIONS = 2;
+    std::string schemas[NUM_VERSIONS];
+    std::string jsonfiles[NUM_VERSIONS];
+    std::vector<uint8_t> binaries[NUM_VERSIONS];
+    flatbuffers::Verifier *verifiers[NUM_VERSIONS];
+
+    flatbuffers::IDLOptions idl_opts;
+    idl_opts.lang_to_generate |= flatbuffers::IDLOptions::kBinary;
+    flatbuffers::Parser parser(idl_opts);
+
+    // Load all the schema versions and their associated data.
+    for (int i = 0; i < NUM_VERSIONS; ++i) {
+      std::string schema = test_data_path + "evolution_test/evolution_v" +
+                           flatbuffers::NumToString(i + 1) + ".fbs";
+      TEST_ASSERT(flatbuffers::LoadFile(schema.c_str(), false, &schemas[i]));
+      std::string json = test_data_path + "evolution_test/evolution_v" +
+                         flatbuffers::NumToString(i + 1) + ".json";
+      TEST_ASSERT(flatbuffers::LoadFile(json.c_str(), false, &jsonfiles[i]));
+
+      TEST_ASSERT(parser.Parse(schemas[i].c_str()));
+      TEST_ASSERT(parser.Parse(jsonfiles[i].c_str()));
+
+      auto bufLen = parser.builder_.GetSize();
+      auto buf = parser.builder_.GetBufferPointer();
+      binaries[i].reserve(bufLen);
+      std::copy(buf, buf + bufLen, std::back_inserter(binaries[i]));
+
+      verifiers[i] = new flatbuffers::Verifier(&binaries[i].front(), bufLen);
+    }
+
+    // Assert that all the verifiers for the different schema versions properly verify any version data.
+    for (int i = 0; i < NUM_VERSIONS; ++i) {
+      TEST_ASSERT(Evolution::V1::VerifyRootBuffer(*verifiers[i]));
+      TEST_ASSERT(Evolution::V2::VerifyRootBuffer(*verifiers[i]));
+    }
+
+    // Test backwards compatibility by reading old data with an evolved schema.
+    auto root_v1_viewed_from_v2 = Evolution::V2::GetRoot(&binaries[0].front());
+    // field 'j' is new in version 2, so it should be null.
+    TEST_EQ(root_v1_viewed_from_v2->j(), NULL);
+    // field 'k' is new in version 2 with a default of 56.
+    TEST_EQ(root_v1_viewed_from_v2->k(), 56);
+    // field 'c' of 'TableA' is new in version 2, so it should be null.
+    TEST_EQ(root_v1_viewed_from_v2->e()->c(), NULL);
+    // 'TableC' was added to field 'c' union in version 2, so it should be null.
+    TEST_EQ(root_v1_viewed_from_v2->c_as_TableC(), NULL);
+    // The field 'c' union should be of type 'TableB' regardless of schema version
+    TEST_ASSERT(root_v1_viewed_from_v2->c_type() == Evolution::V2::Union::TableB);
+    // The field 'f' was renamed to 'ff' in version 2, it should still be readable.
+    TEST_EQ(root_v1_viewed_from_v2->ff()->a(), 16);
+
+    // Test forwards compatibility by reading new data with an old schema.
+    auto root_v2_viewed_from_v1 = Evolution::V1::GetRoot(&binaries[1].front());
+    // The field 'c' union in version 2 is a new table (index = 3) and should still be accessible,
+    // but not interpretable.
+    TEST_EQ(static_cast<uint8_t>(root_v2_viewed_from_v1->c_type()), 3);
+    TEST_NOTNULL(root_v2_viewed_from_v1->c());
+    // The field 'd' enum in verison 2 has new members and should still be accessible, but not interpretable.
+    TEST_EQ(static_cast<int8_t>(root_v2_viewed_from_v1->d()), 3);
+    // The field 'a' in version 2 is deprecated and should return the default value (0) instead of the value stored in
+    // the in the buffer (42).
+    TEST_EQ(root_v2_viewed_from_v1->a(), 0);
+    // The field 'ff' was originally named 'f' in version 1, it should still be readable.
+    TEST_EQ(root_v2_viewed_from_v1->f()->a(), 35);
+#endif
+}
+
 void UnionVectorTest() {
   // load FlatBuffer fbs schema and json.
   std::string schemafile, jsonfile;
@@ -3070,6 +3142,7 @@ int FlatBufferTests() {
     FixedLengthArrayJsonTest(true);
     ReflectionTest(flatbuf.data(), flatbuf.size());
     ParseProtoTest();
+    EvolutionTest();
     UnionVectorTest();
     LoadVerifyBinaryTest();
     GenerateTableTextTest();