This change allows for the generation of fbs files (from proto) that
don't contain name collisions with the protobuf generated C++ code,
allowing both the proto and fbs message types to be linked into the same binary.

StandardCharsets.UTF_8 is already used in FlexBuffersBuilder.

Rare failures occur on AppVeyor in these functions; the failures appear
spurious.

* Include flattests_cpp17 in unit tests when C++17 build is enabled.

* [C++17] Generate generic table factory function.

1. For each table, generate a convenient free-standing factory
   function that allows creating the table in a generic way by
   specifying only the type.  This is the first change in a series
   of changes to make Flatbuffers generated C++ code more friendly
   to code bases that make use of C++ template metaprogramming
   techniques to manage the serialization process.  Example:

     Before :(

       // The name of the Flatbuffers type (and namespace) must
       // be hard-coded when writing the factory function.
       auto monster = MyGame::Example::CreateMonster(fbb, ...);

     After  :)

       using type_to_create = MyGame::Example::Monster;
       // No namespace needed on CreateByTagType.
       auto monster = CreateByTagType((type_to_create*)nullptr,
                                      fbb, ...);

   This feature requires building with C++14 or greater, and thus
   it is guarded behind --cpp-std >= c++17 in the flatbuffers C++
   generator.

2. Fix a CMake bug to include C++17 unit tests in test suite.

* [C++17] Replace standalone variadic factory function with type_traits.

Add a `type_traits` to each table class.  This `type_traits` can be
populated with various compile-time info about the table.  Initially,
we have the Create* function and type, but is extensible in the future.

* Remove empty line and fix stale comments.

* Rename type_traits to Traits and move fwd declaration.

* Fix parameter evaluation order issue and use lambda for scope.

Change-Id: Ia6e032a77983bf1838b8675f51d1c910acc991d8

* Bugfix for Rust generation of union fields named with language keywords

Looking at ParseField, it appears that in the case of unions, an extra field with a `UnionTypeFieldSuffix` is added to the type definition, however, if the name of this field is a keyword in the target language, it isn't escaped.

For example, if generating code for rust for a union field named `type`, flatc will generate a (non-keyword escaped) field named `type_type` for this hidden union field, and one (keyword escaped) called `type_` for the actual union contents.

When the union accessors are generated, they refer to this `type_type` field, but they will escape it mistakenly, generating code like this:

```
  #[inline]
  #[allow(non_snake_case)]
  pub fn type__as_int(&self) -> Option<Int<'a>> {
    if self.type__type() == Type::Int {
      self.type_().map(|u| Int::init_from_table(u))
    } else {
      None
    }
  }
```

Which will fail to build because the field is called `self.type_type()`, not `self.type__type()`.

* [Rust] Add crate-relative use statements for FBS includes.

At present if a flatbuffer description includes a reference to a type in
another file, the generated Rust code needs to be hand-modified to add
the appropriate `use` statements.

This assumes that the dependencies are built into the same crate, which
I think is a reasonable assumption?

* Revert "[Rust] Add crate-relative use statements for FBS includes."

This reverts commit d554d79fecf5afd6da6fb993b30b4cd523a5889a.

* Address comments raised in PR

* Update documentation comments per feedback

* Fix typo

* [rust] Make enum variant names public.

* Update generated test files

* Add test for public enum names

4d1a9f8d9eab9fc6762e03cd862576965a0c6920 inverted the logic around
keeping the include prefix. This change fixes the error.

Add the support to pack using numpy for scalar vectors when numpy is available.

* Add Builder and Table typedefs

This gives us a way to use templates to go from a builder to a table
and back again without having to pass both types in.

* Fix tests/cpp17/generated_cpp17/monster_test_generated.h

Change-Id: Ie34ff580eb2f41ff35f85271b10865f4a14d0dca

This should help with #5672 if I'm reading the report back from
buildkite properly.

Incompatible flag --incompatible_load_cc_rules_from_bzl will break
FlatBuffers once Bazel 1.2.1 is released.

Fixes #5671

For C++11 platforms, absl::string_view is sometimes available. This can
be used for string_view when std::string_view is not available.

* Add support for compatible_with and restricted_to

These attributes have been available in Bazel for years.  Pass them
through so the flatbuffer rules can be used with them.  They let you
constrain which target platform is used.

While we are here, fix gen_reflections to work with bazel.

* Add docs

* New Docker tests for Python with numpy

* print numpy status in test suite

"'this' object cannot be used before all of its fields are assigned to"

Change-Id: Icccdcc0d0be0fe0b87abe0eb28fe1cc91116fcfb

- Missing return statement <- bug!
- Missing hashCode function.

Change-Id: I6333cac72adf8ead92ab2e6c7215650ce4571a73

Change-Id: Ia6c3bf5d7da795db46c0baa8e9c7591de3400517

Change-Id: Iaf64bec068d03dd1b75670e9a28dde7392ebddb5

* Add flatc '--cpp_std' switch and sandbox for C++17 code generator

- Added 'flac --cpp_std legacy' for compatibility with old compilers (VS2010);
- Added experimental switch 'flac --cpp_std c++17' for future development;
- Added C++17 sandbox test_cpp17.cpp;
- C++ code generator generates enums with explicit underlying type to avoid problems with the forward and backward schema compatibility;
- Adjusted CMakeLists.txt, CI and generate code scripts to support of introduced '--cpp_std';

* Fix --cpp_std values: c++0x, c++11, c++17

* Add 'cpp::CppStandard' enum

* Add testing engine into test_cpp17

* Rebase to upstream/master

* Set default '--cpp-std C++0x'

* Fix code generation (--cpp_std C++11) in CMakeLists.txt

- Fix dependency declaration of grpctest target

* Revert --cpp-std for the tests from explicit C++11 to flatc default value (C++0x)

For details, test.cpp/FlexBuffersDeprecatedTest(), and also
https://github.com/google/flatbuffers/issues/5627

Change-Id: I6e86e1138a5777e31055cfa2f79276d44732efbc

* Added missing EndTable() call to VerifyObject()

VerifyObject called VerifyTableStart() but not EndTable(). This made Verifier::VerifyComplexity() increase depth_ with each table, not with the depth of tables.

https://groups.google.com/forum/#!topic/flatbuffers/OpxtW5UFAdg

* Added Check to VerifyAlignment

https://stackoverflow.com/questions/59376308/flatbuffers-verifier-returns-false-without-any-assertion-flatbuffers-debug-veri

* Keep include prefix when converting from proto.

This change preserves the include prefix when generating flatbuffers
from proto (with FBS_GEN_INCLUDES) defined.

* Improve handling of imports in proto conversion.

Previously, there was no runtime flag to make proto->fbs conversion keep
the import structure of a collection of files. This change makes proto
conversion respect the --no-gen-includes flag and skip the output of
"generated" symbols.

* Fix prepare space for writeListInt64 and 

writeListUint64

* Fix align issues

* Make Rust constants public

Otherwise they cannot be accessed by code that consumes the generated
bindings.

* Re-generate test code

* Add a test for enum constants

* Bugfix for Rust generation of union fields named with language keywords

Looking at ParseField, it appears that in the case of unions, an extra field with a `UnionTypeFieldSuffix` is added to the type definition, however, if the name of this field is a keyword in the target language, it isn't escaped.

For example, if generating code for rust for a union field named `type`, flatc will generate a (non-keyword escaped) field named `type_type` for this hidden union field, and one (keyword escaped) called `type_` for the actual union contents.

When the union accessors are generated, they refer to this `type_type` field, but they will escape it mistakenly, generating code like this:

```
  #[inline]
  #[allow(non_snake_case)]
  pub fn type__as_int(&self) -> Option<Int<'a>> {
    if self.type__type() == Type::Int {
      self.type_().map(|u| Int::init_from_table(u))
    } else {
      None
    }
  }
```

Which will fail to build because the field is called `self.type_type()`, not `self.type__type()`.

* [Rust] Add crate-relative use statements for FBS includes.

At present if a flatbuffer description includes a reference to a type in
another file, the generated Rust code needs to be hand-modified to add
the appropriate `use` statements.

This assumes that the dependencies are built into the same crate, which
I think is a reasonable assumption?

* Revert "[Rust] Add crate-relative use statements for FBS includes."

This reverts commit d554d79fecf5afd6da6fb993b30b4cd523a5889a.

* Address comments raised in PR

* Update documentation comments per feedback

* Fix typo

The line where the MessageBuilder was
constructed was commented out (perhaps
an oversight).

The rationale for this option is that JSON clients typically want empty arrays (i.e [] in the JSON) instead of missing properties, but not empty strings when the value isn't set.
--force-empty is kept as-is, i.e. it will force both empty strings and vectors.

Closes #5652

Change-Id: I503fbfaff1d2579807ca71a07cca8363dff75e52

* Split Bazel targets into multiple packages

* Merge /include/BUILD back into /BUILD

Having a static_assert on MSAN and ASAN prevents
the fuzzers from being used with different engines,
like TSAN, UBSAN, … but also with fuzzers that aren't
using MSAN/ASAN like afl for example.

* Flatbuffers Python Object API

Implement the logic to generate the Python object API that can
unpack the data from a buf class into an object class, and pack
the data of an object class to a buf class.

* Fix the build issues

Remove unused parameters and replace auto in the for-loop statement
with std::string to make it compatible with VS2010.

* Fix the build issues.

* Add support for Array type

Added logic to handle Array type in Python Object API. Updated the
generated code accordingly.

* Fix the old style casting from int to char

* Fixed another conversion from int to char

* Fixed the import for typing

Importing typing may cause errors when a machine do not have the
moduel typing installed. This PR fixes the issue by guarding
"import typing" with the "try/except" statement.

* Fix issue of iterating the vector of import list

* Update the generated examples using generate_code.sh

* Fix the import order for typing

The import list was stored in unordered_set, so that each generated
codes may have different import order. Therefore, it failed in the
consistency test where two generated copies need to have exactly the
same apperance.

* Optimize unpack using numpy

Use numpy to unpack vector whenever it is possible to improve unpack
performance.

Also, added codegen command for Python specificly in generate_code.sh,
because --no-includes cannot be turn on for Python.

* Fix the import order

* Update generate_code.bat for windows accordingly

* Replace error message with pass

Avoid printing error message for every Python2 users about typing.
Replace it with pass.

[Clang 10]: definition of implicit copy constructor for 'TableKeyComparatoris deprecated #5649 (#5650)

Add missing semicolon for table field.

* Fix Enum Stringer method when Enum has underscores

Fixes #5481

* Fix go package importing itself when Union has imported members.