synapse/docs/code_style.rst

- Everything should comply with PEP8. Code should pass
  ``pep8 --max-line-length=100`` without any warnings.

- **Indenting**:

  - NEVER tabs. 4 spaces to indent.

  - follow PEP8; either hanging indent or multiline-visual indent depending
    on the size and shape of the arguments and what makes more sense to the
    author. In other words, both this::

      print("I am a fish %s" % "moo")

    and this::

      print("I am a fish %s" %
            "moo")

      and this::

        print(
            "I am a fish %s" %
            "moo",
        )

    ...are valid, although given each one takes up 2x more vertical space than
    the previous, it's up to the author's discretion as to which layout makes
    most sense for their function invocation.  (e.g. if they want to add
    comments per-argument, or put expressions in the arguments, or group
    related arguments together, or want to deliberately extend or preserve
    vertical/horizontal space)

- **Line length**:

  Max line length is 79 chars (with flexibility to overflow by a "few chars" if
  the overflowing content is not semantically significant and avoids an
  explosion of vertical whitespace).

  Use parentheses instead of ``\`` for line continuation where ever possible
  (which is pretty much everywhere).

- **Naming**:

  - Use camel case for class and type names
  - Use underscores for functions and variables.

- Use double quotes ``"foo"`` rather than single quotes ``'foo'``.

- **Blank lines**:

  - There should be max a single new line between:

    - statements
    - functions in a class

  - There should be two new lines between:

    - definitions in a module (e.g., between different classes)

- **Whitespace**:

  There should be spaces where spaces should be and not where there shouldn't
  be:

  - a single space after a comma
  - a single space before and after for '=' when used as assignment
  - no spaces before and after for '=' for default values and keyword arguments.

- **Comments**: should follow the `google code style
  <http://google.github.io/styleguide/pyguide.html?showone=Comments#Comments>`_.
  This is so that we can generate documentation with `sphinx
  <http://sphinxcontrib-napoleon.readthedocs.org/en/latest/>`_. See the
  `examples
  <http://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html>`_
  in the sphinx documentation.

- **Imports**:

  - Prefer to import classes and functions than packages or modules.

    Example::

      from synapse.types import UserID
      ...
      user_id = UserID(local, server)

    is preferred over::

      from synapse import types
      ...
      user_id = types.UserID(local, server)

    (or any other variant).

    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 <https://www.python.org/dev/peps/pep-0008/#imports>`_,
    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``).