diff --git a/docs/contributing.md b/docs/contributing.md
index 53d76ef8..020dbfca 100644
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -1,118 +1,123 @@
-# Contributing to Catch
+# Contributing to Catch2
**Contents**
-[Branches](#branches)
-[Directory structure](#directory-structure)
+[Using Git(Hub)](#using-github)
[Testing your changes](#testing-your-changes)
-[Documenting your code](#documenting-your-code)
-[Examples](#examples)
-[Code constructs to watch out for](#code-constructs-to-watch-out-for)
+[Writing documentation](#writing-documentation)
+[Writing code](#writing-code)
+[CoC](#coc)
-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 As this is liable to drift out of date please raise an issue or, better still, a pull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 `devel` branch for Catch2 v3, and in
+`v2.x` for maintenance updates to the v2 versions.
-_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
+amalgamated distribution files. This means do not include them in your
+git commits!_
-The other directories are `tools/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 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.
-__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!__
## 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 present a small and self-contained snippets of code that
+use Catch2's facilities for specific purpose. Currently they are assumed
+passing if they compile. ExtraTests then are expensive tests, that we
+do not want to run all the time. This can be either because they take
+a long time to run, or because they take a long time to compile, e.g.
+because they test compile time configuration and require separate
+compilation.
+
+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 amalgamated distribution
```
$ cd Catch2
-$ cmake -Bdebug-build -H. -DCMAKE_BUILD_TYPE=Debug
+$ ./tools/scripts/generateAmalgamatedFiles.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.
+If you added new tests, you will likely see `ApprovalTests` failure.
+After you check that the output difference is expected, you should
+run `tools/scripts/approve.py` to confirm them, and include these changes
+in your commit.
-## 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
# Cool feature
@@ -125,6 +130,22 @@ 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 +153,54 @@ 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 +211,8 @@ 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 `` and call the function qualified. The common knowledge that
@@ -188,7 +220,32 @@ there is no difference is wrong, QNX and VxWorks won't compile if you
include the header as `` and call the function unqualified.
-----
+### New source file template
+
+If you are adding new source file, there is a template you should use.
+Specifically, every source file should start with the licence header:
+```cpp
+
+ // Copyright Catch2 Authors
+ // Distributed under the Boost Software License, Version 1.0.
+ // (See accompanying file LICENSE_1_0.txt or copy at
+ // https://www.boost.org/LICENSE_1_0.txt)
+
+ // SPDX-License-Identifier: BSL-1.0
+```
+
+The include guards for header files should follow the pattern `{FILENAME}_INCLUDED`.
+This means that for file `catch_matchers_foo`, the include guard should
+be `CATCH_MATCHERS_FOO_INCLUDED`, for `catch_generators_bar`, the include
+guard should be `CATCH_GENERATORS_BAR_INCLUDED`, and so on.
+
+
+## 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._