Commit c0fe1b52 authored by Dominik Charousset's avatar Dominik Charousset

Update contributions guide

parent 59a85143
This document specifies how to contribute code to CAF.
Git Workflow
============
Please adhere to the following Git naming and commit message conventions.
Having a consistent work flow and style reduces friction and makes organizing
Please adhere to the following Git naming and commit message conventions. Having
a consistent work flow and style reduces friction and makes organizing
contributions a lot easier for all sides.
Branches
--------
- Our main branch is `master`. It reflects the latest development changes for
the next release and should always compile. Nightly versions use the
`master`. Users looking for a production-ready state are encouraged to use
the latest release version instead.
- Push trivial bugfixes (e.g. typos, missing includes, etc.) consisting of a
single commit directly to `master`. Otherwise, implement your changes in a
topic or bugfix branch and file a pull request on GitHub.
- Implement new features and non-trivial changes in a *topic branch* with
naming convention `topic/short-description`.
- Implement fixes for existing issues in a *bugfix branch* with naming
convention `issue/$num`, where `$num` is the issue ID on GitHub.
- Simply use a fork of CAF if you are an external contributor.
Pull Requests
-------------
Check the following steps to prepare for a merge into `master` after completing
work in a topic or bugfix branch (or fork).
- Squash your commits into a single one if necessary. Each commit should
represent a coherent set of changes.
- Wait for a code review and the test results of our CI.
- Address any review feedback and fix all issues reported by the CI.
- A maintainer will merge the pull request when all issues are resolved.
the next release and should always compile. Nightly versions use the `master`
branch. Users looking for a production-ready state are encouraged to use the
latest release version.
- As an external contributor, please fork the project on GitHub and create a
pull request for your proposed changes. Otherwise, follow the guidelines
below.
- After a GitHub issue has been assigned to you, create a branch with naming
convention `issue/$num`, where `$num` is the issue ID on GitHub. Once you are
ready, create a pull request for your branch. You can also file a draft pull
request to get early feedback. In the pull request, put "Closes #$num." or
"Fixes #$num." into the description if the pull request resolves the issue. If
the pull request only partially addresses the issue, use "Relates #$num."
- For smaller changes that do not have a GitHub issue, we use topic branches
with naming convention `topic/$user/short-description`. For example, a branch
for fixing some typos in the documentation by user `johndoe` could be named
`topic/johndoe/fix-doc-typos`.
Commit Message Style
--------------------
......@@ -57,19 +44,49 @@ Commit Message Style
- Optionally add a long description written in full sentences beginning on the
third line. Indent at 72 characters per line.
Pull Requests
-------------
- Squash your commits into a single one before filing a pull request if
necessary. Each commit should represent a coherent set of changes.
- Wait for the results of our CI and fix all issues. Our CI builds CAF with GCC,
Clang, and MSVC on various platforms and makes sure that the code is formatted
correctly. We also measure code coverage and require that new code is covered
by tests.
- We require at least one code review approval before merging a pull request. We
take the review phase seriously and have a high bar for code quality. Multiple
rounds of review are common.
- In case there are multiple rounds of review, please do not squash the commits
until everything is resolved. This makes it easier for reviewers to see what
has changed since the last review.
- A usual commit message for the review phase is "Integrate review feedback" or
"Address review feedback" if you only changed the code according to the review
recommendations.
- A maintainer will merge the pull request when all issues are resolved and the
pull request has been approved by at least one reviewer. If there have been
multiple rounds of review, the maintainer may squash the commits.
Coding Style
============
When contributing source code, please adhere to the following coding style,
which is loosely based on the [Google C++ Style
Guide](https://google.github.io/styleguide/cppguide.html) and the coding
conventions used by the C++ Standard Library.
which is loosely based the C++ Core Guidelines and the coding conventions used
by the C++ Standard Library.
Example for the Impatient
-------------------------
```c++
// libcaf_example/caf/example/my_class.hpp
// File: libcaf_foo/caf/foo/my_class.hpp
// This file is part of CAF, the C++ Actor Framework. See the file LICENSE in
// the main distribution directory for license terms and copyright or visit
// https://github.com/actor-framework/actor-framework/blob/master/LICENSE.
#pragma once
......@@ -77,8 +94,7 @@ Example for the Impatient
// use "//" for regular comments and "///" for doxygen
namespace caf {
namespace example {
namespace caf::foo {
/// This class is only being used as style guide example.
class my_class {
......@@ -91,47 +107,44 @@ public:
/// Destructs `my_class`. Please use Markdown in comments.
~my_class();
// suppress redundant @return if you start the brief description with "Returns"
// omit redundant @return if you start the brief description with "Returns"
/// Returns the name of this instance.
inline const std::string& name() const noexcept {
const std::string& name() const noexcept {
return name_;
}
/// Sets the name of this instance.
inline void name(const std::string& new_name) {
name_ = new_name;
void name(const std::string& new_name) {
name_ = std::move(new_name);
}
/// Prints the name to `std::cout`.
void print_name() const;
/// Does something (maybe).
void do_something();
/// Does something else but is guaranteed to never throw.
void do_something_else() noexcept;
private:
std::string name_;
std::string name_; // Private member variables end with an underscore.
};
} // namespace example
} // namespace caf
} // namespace caf::foo
```
```c++
// libcaf_example/src/example/my_class.cpp
// File: libcaf_foo/caf/foo/my_class.cpp
// This file is part of CAF, the C++ Actor Framework. See the file LICENSE in
// the main distribution directory for license terms and copyright or visit
// https://github.com/actor-framework/actor-framework/blob/master/LICENSE.
#include "caf/example/my_class.hpp"
#include "caf/foo/my_class.hpp"
#include <iostream>
#include <string_view>
namespace caf {
namespace example {
namespace caf::foo {
namespace {
constexpr const char default_name[] = "my object";
constexpr std::string_view default_name = "my object";
} // namespace
......@@ -147,73 +160,37 @@ void my_class::print_name() const {
std::cout << name() << std::endl;
}
void my_class::do_something() {
if (name() == default_name) {
std::cout << "You didn't gave me a proper name, so I "
<< "refuse to do something."
<< std::endl;
} else {
std::cout << "You gave me the name \"" << name()
<< "\"... Do you really think I'm willing to do something "
"for you after insulting me like that?"
<< std::endl;
}
}
void my_class::do_something_else() noexcept {
// Do nothing if we don't have a name.
if (name().empty())
return;
switch (name.front()) {
case 'a':
// handle a
break;
case 'b':
// handle b
break;
default:
handle_default();
}
}
} // namespace example
} // namespace caf
} // namespace caf::foo
```
```c++
// libcaf_example/test/example/my_class.cpp
#define CAF_SUITE example.my_class // name of this test suite
// File: libcaf_foo/caf/foo/my_class.test.cpp
#include "caf/example/my_class.hpp" // header-under-test
// This file is part of CAF, the C++ Actor Framework. See the file LICENSE in
// the main distribution directory for license terms and copyright or visit
// https://github.com/actor-framework/actor-framework/blob/master/LICENSE.
#include "caf/test/dsl.hpp" // caf::test includes
#include <iostream> // standard includes
// ... // other CAF includes
namespace {
struct fixture {};
} // namespace
#include "caf/example/my_class.hpp" // the header-under-test
CAF_TEST_FIXTURE_SCOPE(my_class_tests, fixture)
#include "caf/test/caf_test_main.hpp"
#include "caf/test/test.hpp"
// ... any number of CAF_TEST ...
TEST("my_class::name gets or sets the name") {
caf::foo::my_class x;
check_eq(x.name(), "my object");
x.name("new name");
check_eq(x.name(), "new name");
}
CAF_TEST_FIXTURE_SCOPE_END()
CAF_TEST_MAIN()
```
General
-------
- Use 2 spaces per indentation level.
- Use at most 80 characters per line.
- Never use tabs.
Source code must be formatted using `clang-format` with the configuration file
`.clang-format` in the root directory of the repository. The following rules are
not enforced by `clang-format` and must be applied manually:
- Never use C-style casts.
......@@ -222,12 +199,11 @@ General
- Only separate functions with vertical whitespaces and use comments to
document logical blocks inside functions.
- Use `.hpp` as suffix for header files and `.cpp` as suffix for implementation
files.
- Bind `*` and `&` to the *type*, e.g., `const std::string& arg`.
- Use `.hpp` as suffix for header files, `.cpp` as suffix for implementation
files and `.test.cpp` as suffix for unit tests.
- Never increase the indentation level for namespaces and access modifiers.
- Use `#include "caf/foo/bar.hpp"` for CAF headers and `#include <foo/bar.hpp>`
for third-party headers.
- Use the order `public`, `protected`, and then `private` in classes.
......@@ -235,82 +211,31 @@ General
immediately or if you actually want a type conversion. In the latter case,
provide a comment why this conversion is necessary.
- Never use unwrapped, manual resource management such as `new` and `delete`.
- Prefer `using T = X` over `typedef X T`.
- Insert a whitespaces after keywords: `if (...)`, `template <...>`,
`while (...)`, etc.
- Put opening braces on the same line:
```c++
void foo() {
// ...
}
```
- Use standard order for readability: C standard libraries, C++ standard
libraries, OS-specific headers (usually guarded by `ifdef`), other libraries,
and finally (your) CAF headers. Include `caf/config.hpp` before the standard
headers if you need to include platform-dependent headers. Use angle brackets
for system includes and doublequotes otherwise.
```c++
// example.hpp
#include <vector>
#include <sys/types.h>
#include "3rd/party.h"
- Never use unwrapped, manual resource management such as `new` and `delete`,
except when implementing a smart pointer or a similar abstraction.
#include "caf/fwd.hpp"
```
Put the implemented header always first in a `.cpp` file.
```c++
// example.cpp
#include "caf/example.hpp" // header for this .cpp file
#include "caf/config.hpp" // needed for #ifdef guards
#include <algorithm>
#ifdef CAF_WINDOWS
#include <windows.h>
#else
#include <sys/socket.h>
#endif
#include "some/other/library.h"
#include "caf/actor.hpp"
```
- Prefer algorithms over manual loops.
- Put output parameters in functions before input parameters if unavoidable.
This follows the parameter order from the STL.
- Prefer `using T = X` over `typedef X T`.
- Protect single-argument constructors with `explicit` to avoid implicit
conversions.
- Use `noexcept` whenever it makes sense and as long as it does not limit future
design space. Move construction and assignment are natural candidates for
`noexcept`.
- Use `noexcept` and attributes such as `[[nodiscard]]` whenever it makes sense
and as long as it does not limit future design space. For example, move
construction and assignment are natural candidates for `noexcept`.
Naming
------
- All names except macros and template parameters should be
lower case and delimited by underscores.
- All names except macros and template parameters should be lower case and
delimited by underscores, i.e., `snake_case`.
- Template parameter names should be written in CamelCase.
- Template parameter names should be written in `CamelCase`.
- Types and variables should be nouns, while functions performing an action
should be "command" verbs. Classes used to implement metaprogramming
functions also should use verbs, e.g., `remove_const`.
should be "command" verbs. Classes used to implement metaprogramming functions
also should use verbs, e.g., `remove_const`.
- Private and protected member variables use the suffix `_` while getter *and*
setter functions use the name without suffix:
......@@ -322,7 +247,7 @@ Naming
// nop
}
const std::string& name() const {
const std::string& name() const noexcept {
return name_
}
......@@ -335,132 +260,23 @@ Naming
};
```
- Use `T` for generic, unconstrained template parameters and `x`
for generic function arguments. Suffix both with `s` for
template parameter packs and lists:
```c++
template <class... Ts>
void print(const Ts&... xs) {
// ...
}
void print(const std::vector<T>& xs) {
// ...
}
```
Headers
-------
- Each `.cpp` file has an associated `.hpp` file.
Exceptions to this rule are unit tests and `main.cpp` files.
- Each class has its own pair of header and implementation files and the
relative path for the files are derived from the full class name. For
example, the header file for `caf::example::my_class` of `libcaf_example` is
located at `libcaf_example/caf/example/my_class.hpp` and the source file at
`libcaf_example/src/example/my_class.cpp`.
- All header files use `#pragma once` to prevent multiple inclusion.
- Do not `#include` when a forward declaration suffices.
- Each library component must provide a `fwd.hpp` header providing forward
declarations for all types used in the user API.
- Each library component should provide a `fwd.hpp` header providing forward
declarations for its public types.
- Each library component should provide an `all.hpp` header that contains the
main page for the documentation and includes all headers for the user API.
- Use `inline` for small functions (rule of thumb: 10 lines or less).
Breaking Statements
-------------------
- Only include the forwarding header when a forward declaration suffices.
- Break constructor initializers after the comma, use two spaces for
indentation, and place each initializer on its own line (unless you don't
need to break at all):
```c++
my_class::my_class()
: my_base_class(some_function()),
greeting_("Hello there! This is my_class!"),
some_bool_flag_(false) {
// ok
}
other_class::other_class() : name_("tommy"), buddy_("michael") {
// ok
}
```
- Break function arguments after the comma for both declaration and invocation:
```c++
intptr_t channel::compare(const abstract_channel* lhs,
const abstract_channel* rhs) {
// ...
}
```
- Break before tenary operators and before binary operators:
```c++
if (today_is_a_sunny_day()
&& it_is_not_too_hot_to_go_swimming()) {
// ...
}
```
Template Metaprogramming
------------------------
Despite its power, template metaprogramming came to the language pretty
much by accident. Templates were never meant to be used for compile-time
algorithms and type transformations. This is why C++ punishes metaprogramming
with an insane amount of syntax noise. In CAF, we make excessive use of
templates. To keep the code readable despite all the syntax noise, we have some
extra rules for formatting metaprogramming code.
- Break `using name = ...` statements always directly after `=` if it
does not fit in one line.
- Consider the *semantics* of a metaprogramming function. For example,
`std::conditional` is an if-then-else construct. Hence, place the if-clause
on its own line and do the same for the two cases.
- Use one level of indentation per "open" template and place the closing `>`,
`>::type` or `>::value` on its own line. For example:
```c++
using optional_result_type =
typename std::conditional<
std::is_same<result_type, void>::value,
bool,
optional<result_type>
>::type;
// think of it as the following (not valid C++):
auto optional_result_type =
conditional {
if result_type == void
then bool
else optional<result_type>
};
```
- Note that this is not necessary when simply defining a type alias.
When dealing with "ordinary" templates, indenting based on the position of
the opening `<` is ok, e.g.:
```c++
using response_handle_type = response_handle<Subtype, message,
ResponseHandleTag>;
```
- Implement small functions inline (rule of thumb: 5 lines or less).
Preprocessor Macros
-------------------
- Use macros if and only if you can't get the same result by using inline
functions or proper constants.
functions, templates, or proper constants.
- Macro names use the form `CAF_<COMPONENT>_<NAME>`.
......@@ -469,9 +285,10 @@ Comments
- Start Doxygen comments with `///`.
- Use Markdown instead of Doxygen formatters.
- Use Markdown syntax in Doxygen comments.
- Use `@cmd` rather than `\cmd`.
- Use `//` to define basic comments that should not be processed by Doxygen.
- Never use `/* ... */` C-style comments.
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