Rewrite the contributing documentation

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<a id="top"></a>
# Contributing to Catch
# Contributing to Catch2
**Contents**<br>
[Branches](#branches)<br>
[Directory structure](#directory-structure)<br>
[Using Git(Hub)](#using-github)<br>
[Testing your changes](#testing-your-changes)<br>
[Documenting your code](#documenting-your-code)<br>
[Examples](#examples)<br>
[Code constructs to watch out for](#code-constructs-to-watch-out-for)<br>
[Writing documentation](#writing-documentation)<br>
[Writing code](#writing-code)<br>
[CoC](#coc)<br>
So you want to contribute something to Catch? That's great! Whether it's a bug fix, a new feature, support for
additional compilers - or just a fix to the documentation - all contributions are very welcome and very much appreciated.
Of course so are bug reports and other comments and questions.
So you want to contribute something to Catch2? That's great! Whether it's
a bug fix, a new feature, support for additional compilers - or just
a fix to the documentation - all contributions are very welcome and very
much appreciated. Of course so are bug reports, other comments, and
questions, but generally it is a better idea to ask questions in our
[Discord](https://discord.gg/4CWS9zD), than in the issue tracker.
If you are contributing to the code base there are a few simple guidelines to keep in mind. This also includes notes to
help you find your way around. As this is liable to drift out of date please raise an issue or, better still, a pull
request for this file, if you notice that.
## Branches
This page covers some guidelines and helpful tips for contributing
to the codebase itself.
Ongoing development is currently on _master_. At some point an integration branch will be set-up and PRs should target
that - but for now it's all against master. You may see feature branches come and go from time to time, too.
## Using Git(Hub)
## Directory structure
Ongoing development happens in the `master` branch for Catch2 v2, and in
`dev-v3` for the next major version, v3.
_Users_ of Catch primarily use the single header version. _Maintainers_ should work with the full source (which is still,
primarily, in headers). This can be found in the `include` folder. There are a set of test files, currently under
`projects/SelfTest`. The test app can be built via CMake from the `CMakeLists.txt` file in the root, or you can generate
project files for Visual Studio, XCode, and others (instructions in the `projects` folder). If you have access to CLion,
it can work with the CMake file directly.
Commits should be small and atomic. A commit is atomic when, after it is
applied, the codebase, tests and all, still works as expected. Small
commits are also prefered, as they make later operations with git history,
whether it is bisecting, reverting, or something else, easier.
As well as the runtime test files you'll also see a `SurrogateCpps` directory under `projects/SelfTest`.
This contains a set of .cpp files that each `#include` a single header.
While these files are not essential to compilation they help to keep the implementation headers self-contained.
At time of writing this set is not complete but has reasonable coverage.
If you add additional headers please try to remember to add a surrogate cpp for it.
_When submitting a pull request please do not include changes to the
single include. This means do not include them in your git commits!_
The other directories are `scripts` which contains a set of python scripts to help in testing Catch as well as
generating the single include, and `docs`, which contains the documentation as a set of markdown files.
__When submitting a pull request please do not include changes to the single include, or to the version number file
as these are managed by the scripts!__
When addressing review comments in a MR, please do not rebase/squash the
commits immediately. Doing so makes it harder to review the new changes,
slowing down the process of merging a MR. Instead, when addressing review
comments, you should append new commits to the branch and only squash
them into other commits when the MR is ready to be merged. We recommend
creating new commits with `git commit --fixup` (or `--squash`) and then
later squashing them with `git rebase --autosquash` to make things easier.
## Testing your changes
Obviously all changes to Catch's code should be tested. If you added new
functionality, you should add tests covering and showcasing it. Even if you have
only made changes to Catch internals (i.e. you implemented some performance
improvements), you should still test your changes.
_Note: Running Catch2's tests requires Python3_
This means 2 things
* Compiling Catch's SelfTest project:
Catch2 has multiple layers of tests that are then run as part of our CI.
The most obvious one are the unit tests compiled into the `SelfTest`
binary. These are then used in "Approval tests", which run (almost) all
tests from `SelfTest` through a specific reporter and then compare the
generated output with a known good output ("Baseline"). By default, new
tests should be placed here.
However, not all tests can be written as plain unit tests. For example,
checking that Catch2 orders tests randomly when asked to, and that this
random ordering is subset-invariant, is better done as an integration
test using an external check script. Catch2 integration tests are written
using CTest, either as a direct command invocation + pass/fail regex,
or by delegating the check to a Python script.
There are also two more kinds of tests, examples and "ExtraTests".
Examples serve as a compilation test on the single-header distribution,
and present a small and self-contained snippets of using Catch2 for
writing tests. ExtraTests then are tests that either take a long time
to run, or require separate compilation, e.g. because of testing compile
time configuration options, and take a long time because of that.
Both of these are compiled against the single-header distribution of
Catch2, and thus might require you to regenerate it manually. This is
done by calling the `generateSingleHeader.py` script in `scripts`.
Examples and ExtraTests are not compiled by default. To compile them,
add `-DCATCH_BUILD_EXAMPLES=ON` and `-DCATCH_BUILD_EXTRA_TESTS=ON` to
the invocation of CMake configuration step.
Bringing this all together, the steps below should configure, build,
and run all tests in the `Debug` compilation.
1. Regenerate the single header distribution
```
$ cd Catch2
$ cmake -Bdebug-build -H. -DCMAKE_BUILD_TYPE=Debug
$ ./scripts/generateSingleHeader.py
```
2. Configure the full test build
```
$ cmake -Bdebug-build -H. -DCMAKE_BUILD_TYPE=Debug -DCATCH_BUILD_EXAMPLES=ON -DCATCH_BUILD_EXTRA_TESTS=ON
```
3. Run the actual build
```
$ cmake --build debug-build
```
because code that does not compile is evidently incorrect. Obviously,
you are not expected to have access to all the compilers and platforms
supported by Catch2, but you should at least smoke test your changes
on your platform. Our CI pipeline will check your PR against most of
the supported platforms, but it takes an hour to finish -- compiling
locally takes just a few minutes.
* Running the tests via CTest:
4. Run the tests using CTest
```
$ cd debug-build
$ ctest -j 2 --output-on-failure
$ ctest -j 4 --output-on-failure -C Debug
```
__Note:__ When running your tests with multi-configuration generators like
Visual Studio, you might get errors "Test not available without configuration."
You then have to pick one configuration (e.g. ` -C Debug`) in the `ctest` call.
If you added new tests, approval tests are very likely to fail. If they
do not, it means that your changes weren't run as part of them. This
_might_ be intentional, but usually is not.
The approval tests compare current output of the SelfTest binary in various
configurations against known good outputs. The reason it fails is,
_usually_, that you've added new tests but have not yet approved the changes
they introduce. This is done with the `scripts/approve.py` script, but
before you do so, you need to check that the introduced changes are indeed
intentional.
## Documenting your code
## Writing documentation
If you have added new feature to Catch2, it needs documentation, so that
other people can use it as well. This section collects some technical
information that you will need for updating Catch2's documentation, and
possibly some generic advise as well.
### Technicalities
First, the technicalities:
* We introduced version tags to the documentation, which show users in
which version a specific feature was introduced. This means that newly
written documentation should be tagged with a placeholder, that will
be replaced with the actual version upon release. There are 2 styles
of placeholders used through the documentation, you should pick one that
fits your text better (if in doubt, take a look at the existing version
tags for other features).
* `> [Introduced](link-to-issue-or-PR) in Catch X.Y.Z` - this
placeholder is usually used after a section heading
* `> X (Y and Z) was [introduced](link-to-issue-or-PR) in Catch X.Y.Z`
- this placeholder is used when you need to tag a subpart of something,
e.g. list
* Crosslinks to different pages should target the `top` anchor, like this
`[link to contributing](contributing.md#top)`.
* If you have introduced a new document, there is a simple template you
should use. It provides you with the top anchor mentioned above, and also
with a backlink to the top of the documentation:
should use. It provides you with the top anchor mentioned to link to
(more below), and also with a backlink to the top of the documentation:
```markdown
<a id="top"></a>
# Cool feature
@ -125,6 +126,22 @@ Text that explains how to use the cool feature.
[Home](Readme.md#top)
```
* Crosslinks to different pages should target the `top` anchor, like this
`[link to contributing](contributing.md#top)`.
* We introduced version tags to the documentation, which show users in
which version a specific feature was introduced. This means that newly
written documentation should be tagged with a placeholder, that will
be replaced with the actual version upon release. There are 2 styles
of placeholders used through the documentation, you should pick one that
fits your text better (if in doubt, take a look at the existing version
tags for other features).
* `> [Introduced](link-to-issue-or-PR) in Catch X.Y.Z` - this
placeholder is usually used after a section heading
* `> X (Y and Z) was [introduced](link-to-issue-or-PR) in Catch X.Y.Z`
- this placeholder is used when you need to tag a subpart of something,
e.g. a list
* For pages with more than 4 subheadings, we provide a table of contents
(ToC) at the top of the page. Because GitHub markdown does not support
automatic generation of ToC, it has to be handled semi-manually. Thus,
@ -132,44 +149,54 @@ if you've added a new subheading to some page, you should add it to the
ToC. This can be done either manually, or by running the
`updateDocumentToC.py` script in the `scripts/` folder.
### Contents
Now, for the generic tips:
* Usage examples are good
* Don't be afraid to introduce new pages
* Try to be reasonably consistent with the surrounding documentation
Now, for some content tips:
## Examples
* Usage examples are good. However, having large code snippets inline
can make the documentation less readable, and so the inline snippets
should be kept reasonably short. To provide more complex compilable
examples, consider adding new .cpp file to `examples/`.
The examples/ directory contains some example tests which should compile and
run to show how to use Catch2. The code being tested should be trivial as the
purpose of the examples is to show how the tests work.
* Don't be afraid to introduce new pages. The current documentation
tends towards long pages, but a lot of that is caused by legacy, and
we know that some of the pages are overly big and unfocused.
The examples in the `examples/` directory are not built by default. To compile
them add `-DCATCH_BUILD_EXAMPLES=ON` to your cmake command line. There will
then be an `examples/` directory in your build directory, containing the
resulting test programs.
* When adding information to an existing page, please try to keep your
formatting, style and changes consistent with the rest of the page.
In general each file in `examples/` compiles to a stand-alone test program for
clarity.
* Any documentation has multiple different audiences, that desire
different information from the text. The 3 basic user-types to try and
cover are:
* A beginner to Catch2, who requires closer guidance for the usage of Catch2.
* Advanced user of Catch2, who want to customize their usage.
* Experts, looking for full reference of Catch2's capabilities.
The examples are compiled against the local copy of the _single header_ version
of catch. If you are building from git then this might not be up to date with
changes in the _full source_ version. Before trying to build the examples, go
to the top level of the source tree, and run the python script to prepare the
single header version (this requires Python3 to be installed):
```
./scripts/generateSingleHeader.py
```
__When submitting a pull request please do not include changes to the single
include. This means do not include them in your git commits!__
## Writing code
## Code constructs to watch out for
If want to contribute code, this section contains some simple rules
and tips on things like code formatting, code constructions to avoid,
and so on.
### Formatting
To make code formatting simpler for the contributors, Catch2 provides
its own config for `clang-format`. However, because it is currently
impossible to replicate existing Catch2's formatting in clang-format,
using it to reformat a whole file would cause massive diffs. To keep
the size of your diffs reasonable, you should only use clang-format
on the newly changed code.
### Code constructs to watch out for
This section is a (sadly incomplete) listing of various constructs that
are problematic and are not always caught by our CI infrastructure.
### Naked exceptions and exceptions-related function
#### Naked exceptions and exceptions-related function
If you are throwing an exception, it should be done via `CATCH_ERROR`
or `CATCH_RUNTIME_ERROR` in `catch_enforce.h`. These macros will handle
@ -180,7 +207,8 @@ CI, but luckily there should not be too many reasons to use these.
However, if you do, they should be kept behind a
`CATCH_CONFIG_DISABLE_EXCEPTIONS` macro.
### Unqualified usage of functions from C's stdlib
#### Unqualified usage of functions from C's stdlib
If you are using a function from C's stdlib, please include the header
as `<cfoo>` and call the function qualified. The common knowledge that
@ -188,7 +216,12 @@ there is no difference is wrong, QNX and VxWorks won't compile if you
include the header as `<cfoo>` and call the function unqualified.
----
## CoC
This project has a [CoC](../CODE_OF_CONDUCT.md). Please adhere to it
while contributing to Catch2.
-----------
_This documentation will always be in-progress as new information comes
up, but we are trying to keep it as up to date as possible._