Contribution Guidelines

Code Style

When contributing code, in addition to following the C++ Core Guidelines, please follow the same design guidelines and style guidelines as mongodb/mongo. Additions and exceptions are listed below. For anything that isn't explicitly covered here, default to the Google C++ Style Guide. Running clang-format with our configuration file, mongo-cxx-driver/.clang-format, will help ensure your code conforms to the above standards.

Commit Messages

If a pull-request addresses a JIRA ticket, for a single-commit PR, prefix the subject line with the ticket ID. (For a multi-commit PR, we will add the ID later when we squash or merge it.)

CXX-883 Add commit message conventions to CONTRIBUTING.md

Capitalize subject lines and don't use a trailing period. Keep the subject at most 70 characters long. Use active voice! Imagine this preamble to get your phrasing right:

If applied, this commit will... [your subject line]

See Chris Beams' How to write a git commit message for more good guidelines to follow.

Lifecycle Methods

• default-or-argument-bearing 'user' constructors

• declaration-or-deletion-of-copy-constructor

• declaration-or-deletion-of-move-constructor

• declaration-or-deletion-of-copy-assignment-operator

• declaration-or-deletion-of-move-assignment-operator

• declaration-of-dtor

Headers

Public headers must have a ".hpp" suffix. Private headers must have a ".hh" suffix.

General structure:

• License

• Include Guard (#pragma once)

• Header Prelude

• System Headers <vector> (alphabetical order)

• Driver Headers <path/to/header.hpp> (alphabetical order)

• Open Namespace mongocxx

• inline namespace v_noabi {

• Code

• } // namespace v_noabi

• Close Namespace mongocxx

• Header Postlude

Example:

// Copyright 2018-present MongoDB Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include <driver/config/prelude.hpp>
#include <vector>
#include <driver/blah.hpp>
namespace mongocxx {
inline namespace v_noabi {
   // Declarations
   // Inline Implementations
}  // namespace v_noabi
}  // namespace mongocxx
#include <driver/config/postlude.hpp>

Class Declarations

Guidelines:

• Blank line at beginning and end of class declaration

• Public section up top / private at bottom

• Lifecycle methods first (see rules above)

• Private Member Ordering

  • Friendships

  • Private Constructors

  • Private Methods

  • Private Variables

Example:

class foo {
    public:
      foo();
      foo(foo&& other) noexcept;
      foo& operator=(foo&& other) noexcept;
      ~foo();
    private:
      friend baz;
      class MONGOCXX_PRIVATE impl;
      std::unique_ptr<impl> _impl;
};

Inlines

• Define outside of class declaration

• Specify inline keyword in declaration and definition (for clarity)

Relational Operators

• Prefer to use free functions