diff --git a/changelog.d/5719.misc b/changelog.d/5719.misc
new file mode 100644
index 0000000000..6d5294724c
--- /dev/null
+++ b/changelog.d/5719.misc
@@ -0,0 +1 @@
+Update the coding style document.
diff --git a/docs/code_style.rst b/docs/code_style.rst
index e3ca626bfd..39ac4ebedc 100644
--- a/docs/code_style.rst
+++ b/docs/code_style.rst
@@ -1,4 +1,8 @@
-# Code Style
+Code Style
+==========
+
+Formatting tools
+----------------
The Synapse codebase uses a number of code formatting tools in order to
quickly and automatically check for formatting (and sometimes logical) errors
@@ -6,20 +10,20 @@ in code.
The necessary tools are detailed below.
-## Formatting tools
+- **black**
-The Synapse codebase uses [black](https://pypi.org/project/black/) as an
-opinionated code formatter, ensuring all comitted code is properly
-formatted.
+ The Synapse codebase uses `black `_ as an
+ opinionated code formatter, ensuring all comitted code is properly
+ formatted.
-First install ``black`` with::
+ First install ``black`` with::
- pip install --upgrade black
+ pip install --upgrade black
-Have ``black`` auto-format your code (it shouldn't change any
-functionality) with::
+ Have ``black`` auto-format your code (it shouldn't change any functionality)
+ with::
- black . --exclude="\.tox|build|env"
+ black . --exclude="\.tox|build|env"
- **flake8**
@@ -54,17 +58,16 @@ functionality is supported in your editor for a more convenient development
workflow. It is not, however, recommended to run ``flake8`` on save as it
takes a while and is very resource intensive.
-## General rules
+General rules
+-------------
- **Naming**:
- Use camel case for class and type names
- Use underscores for functions and variables.
-- Use double quotes ``"foo"`` rather than single quotes ``'foo'``.
-
-- **Comments**: should follow the `google code style
- `_.
+- **Docstrings**: should follow the `google code style
+ `_.
This is so that we can generate documentation with `sphinx
`_. See the
`examples
@@ -73,6 +76,8 @@ takes a while and is very resource intensive.
- **Imports**:
+ - Imports should be sorted by ``isort`` as described above.
+
- Prefer to import classes and functions rather than packages or modules.
Example::
@@ -92,25 +97,84 @@ takes a while and is very resource intensive.
This goes against the advice in the Google style guide, but it means that
errors in the name are caught early (at import time).
- - Multiple imports from the same package can be combined onto one line::
-
- from synapse.types import GroupID, RoomID, UserID
-
- An effort should be made to keep the individual imports in alphabetical
- order.
-
- If the list becomes long, wrap it with parentheses and split it over
- multiple lines.
-
- - As per `PEP-8 `_,
- imports should be grouped in the following order, with a blank line between
- each group:
-
- 1. standard library imports
- 2. related third party imports
- 3. local application/library specific imports
-
- - Imports within each group should be sorted alphabetically by module name.
-
- Avoid wildcard imports (``from synapse.types import *``) and relative
imports (``from .types import UserID``).
+
+Configuration file format
+-------------------------
+
+The `sample configuration file <./sample_config.yaml>`_ acts as a reference to
+Synapse's configuration options for server administrators. Remember that many
+readers will be unfamiliar with YAML and server administration in general, so
+that it is important that the file be as easy to understand as possible, which
+includes following a consistent format.
+
+Some guidelines follow:
+
+* Sections should be separated with a heading consisting of a single line
+ prefixed and suffixed with ``##``. There should be **two** blank lines
+ before the section header, and **one** after.
+
+* Each option should be listed in the file with the following format:
+
+ * A comment describing the setting. Each line of this comment should be
+ prefixed with a hash (``#``) and a space.
+
+ The comment should describe the default behaviour (ie, what happens if
+ the setting is omitted), as well as what the effect will be if the
+ setting is changed.
+
+ Often, the comment end with something like "uncomment the
+ following to \".
+
+ * A line consisting of only ``#``.
+
+ * A commented-out example setting, prefixed with only ``#``.
+
+ For boolean (on/off) options, convention is that this example should be
+ the *opposite* to the default (so the comment will end with "Uncomment
+ the following to enable [or disable] \." For other options,
+ the example should give some non-default value which is likely to be
+ useful to the reader.
+
+* There should be a blank line between each option.
+
+* Where several settings are grouped into a single dict, *avoid* the
+ convention where the whole block is commented out, resulting in comment
+ lines starting ``# #``, as this is hard to read and confusing to
+ edit. Instead, leave the top-level config option uncommented, and follow
+ the conventions above for sub-options. Ensure that your code correctly
+ handles the top-level option being set to ``None`` (as it will be if no
+ sub-options are enabled).
+
+* Lines should be wrapped at 80 characters.
+
+Example::
+
+ ## Frobnication ##
+
+ # The frobnicator will ensure that all requests are fully frobnicated.
+ # To enable it, uncomment the following.
+ #
+ #frobnicator_enabled: true
+
+ # By default, the frobnicator will frobnicate with the default frobber.
+ # The following will make it use an alternative frobber.
+ #
+ #frobincator_frobber: special_frobber
+
+ # Settings for the frobber
+ #
+ frobber:
+ # frobbing speed. Defaults to 1.
+ #
+ #speed: 10
+
+ # frobbing distance. Defaults to 1000.
+ #
+ #distance: 100
+
+Note that the sample configuration is generated from the synapse code and is
+maintained by a script, ``scripts-dev/generate_sample_config``. Making sure
+that the output from this script matches the desired format is left as an
+exercise for the reader!