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CONTRIBUTING.md

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Contributing Guidelines

We follow the MongoDB Server Code Style except:

  • We use GUID include-guards rather than #pragma once
  • File names match class names e.g. class FooBar will be found in FooBar.hpp and FooBar.cpp rather than foo_bar.hpp.

We have not yet officially brought over the clang-formatter settings from the server.

Don't Get Cute

Please avoid:

  • Complicated macros (e.g. __VA_ARGS__ or #ifdef excluding include-guards)
  • Macros for syntax tokens (e.g. class MyClass : PRIVATE_SUBCLASS Y or namespace SOME_NAMESPACE)
  • Conditional-compilation (we strive to only use widely-supported standard C++ features)
  • Compiler-specific features
  • std::experimental
  • Code-generation (e.g. generating C++ from another language, including CMake)

Many editors and IDEs have a hard time if code hides lots of things behind macros or code-generation or otherwise uses cleverness. While there is a lot of power in macros and code-generation, for the time-being we are valuing wide editor support and simplicity of conventional methods.

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.)

ABC-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.

Headers

Naming and bureaucracy:

  • Public (exposed) header files belong in include directories.
  • Public headers must have a .hpp suffix.
  • Private headers must have a .hh suffix.
  • Header file names are in snake_case, but headers defining a single class are PascalCase.
  • Class names are in PascalCase, and local/member variables are lowerCamelCase.
  • Member variables (class properties) have leading underscores.
  • Method parameters do not have leading or trailing underscores.

General header file structure:

  • Include Guard (#ifndef HEADER_{uuid}_INCLUDED #define HEADER_{uuid}_INCLUDED). Use uuidgen | sed s/-/_/g to generate {uuid} for new files.
  • System Headers <vector> (alphabetical order)
  • Blank line
  • Local headers <genny/foo.hpp> (alphabetical order)
  • Open Namespace genny
  • Code
  • Close Namespace genny

(Helpful tip: make a shell alias for the include string: alias huuid="echo \"HEADER_\$(uuidgen | sed s/-/_/g)_INCLUDED\"")

Example header file:

#ifndef HEADER_9854B7E9_CAFF_4CD3_8A48_BD5E6A368C96_INCLUDED
#define HEADER_9854B7E9_CAFF_4CD3_8A48_BD5E6A368C96_INCLUDED

#include <string>
#include <vector>

#include <genny/bar.hpp>
#include <genny/foo.hpp>

namespace genny {

// Declarations
// Inline Implementations

}  // namespace genny

#endif  // HEADER_9854B7E9_CAFF_4CD3_8A48_BD5E6A368C96_INCLUDED

Class Declarations

Guideline and ordering:

  • Blank line at beginning and end of class declaration

  • Class names in PascalCase

  • Public section up top:

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

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

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

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

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

    • declaration-of-dtor

    • Public methods

  • Passkey/pseudo-private methods within public section

  • Private section on bottom:

    • Friendships
    • Private Constructors
    • Private Methods
    • Private Variables (leading underscore and lowerCamelCase)

  • Blank line at end of class declaration.

Example:

#ifndef HEADER_82C204F5_26C2_4B39_9469_9FE242037891_INCLUDED
#define HEADER_82C204F5_26C2_4B39_9469_9FE242037891_INCLUDED

#include <string>
#include <vector>

#include <gennylib/Foo.hpp>

namespace genny {

class Foo {

public:
    Foo();

    Foo(Foo&& other) noexcept;
    Foo& operator=(Foo&& other) noexcept;

    ~Foo();

    std::vector<int> explode(const std::string& y);

private:
    friend class Baz;

    class impl;
    std::unique_ptr<impl> _impl;

};

}  // namespace genny

#endif  // HEADER_82C204F5_26C2_4B39_9469_9FE242037891_INCLUDED

Inlines

  • Define outside of class declaration
  • Specify inline keyword in declaration and definition (for clarity)

Relational Operators

  • Prefer to use free functions

Use Scoped Enums

  • Use scoped enums (enum class) wherever possible
  • Use k prefixes for enum values e.g. enum class Color { kRed, kBlue };

Catch2

Genny uses Catch2 as its test framework. If you'd like to make changes to the vendored copy of Catch2 (e.g. to upgrade to a newer copy) Please make sure you read the README in the Catch2 directory before making changes.