Limnoria-doc/develop/style.rst

****************
Style Guidelines
****************

**Note:** Code not following these style guidelines fastidiously is likely
not to be accepted into the Limnoria core.

* Read :pep:`8` (Guido's Style Guide) and know that we use almost all the
  same style guidelines.
  - We use a maximum of 79 characters per line and 4 spaces per indentation level
  - Exception: method and function names generally use camelCase for consistency
    with existing code.

* Raw strings (``r''`` or ``r""``) should be used for regular expressions.

* Unless absolutely required by some external force, imports should be ordered
  by the string length of the module imported.  I just think it looks
  prettier.

* Database filenames should generally begin with the name of the plugin and
  the extension should be 'db'.  plugins.DBHandler does this already.

* Whenever creating a file descriptor or socket, keep a reference around and
  be sure to close it.  There should be no code like this::

    s = urllib.request.urlopen('url').read()

  Instead, do this::

    fd = urllib.request.urlopen('url')
    try:
        s = fd.read()
    finally:
        fd.close()

  This is to be sure the bot doesn't leak file descriptors.

* All plugin files should include a docstring describing what the plugin does.
  This docstring will be returned when the user is configuring the plugin.

* All plugin classes should also include a docstring describing how to do
  things with the plugin; this docstring will be returned when the user
  requests help on a plugin name.

* Method docstrings in classes deriving from callbacks.Privmsg should include
  an argument list as their first line, and after that a blank line followed
  by a longer description of what the command does.  The argument list is used
  by the ``syntax`` command, and the longer description is used by the
  ``help`` command.

* Whenever joining more than two strings, use f-strings or string
  interpolation, not addition::

    s = x + y + z # Bad.
    s = '%s%s%s' % (x, y, z) # Good.
    s = ''.join([x, y, z]) # Better, but not as general.
    s = f'{x}{y}{z}' # Best.

* When writing strings that have formatting characters in them, don't use
  anything but ``%s`` unless you absolutely must.  Avoid ``%d`` in particular
  because it's not as general and is likely to throw type errors if you make a
  mistake.

* As a corollary to the above, note that sometimes ``%f`` is used, but on when
  floats need to be formatted, e.g., ``%.2f``.

* Use the log module to its fullest; when you need to print some values to
  debug, use self.log.debug to do so, and leave those statements in the code
  (commented out) so they can later be re-enabled.  Remember that once code is
  buggy, it tends to have more bugs, and you'll probably need those print
  statements again.

* While on the topic of logs, note that we do not use % (i.e., str.__mod__)
  with logged strings; we simple pass the format parameters as additional
  arguments.  The reason is simple: the logging module supports it, and it's
  cleaner (fewer tokens/glyphs) to read.

* While still on the topic of logs, it's also important to pick the
  appropriate log level for given information.

  * DEBUG:  Appropriate to tell a programmer *how* we're doing something
    (i.e., debugging printfs, basically).  If you're trying to figure out why
    your code doesn't work, DEBUG is the new printf -- use that, and leave the
    statements in your code.

  * INFO:   Appropriate to tell a user *what* we're doing, when what we're
    doing isn't important for the user to pay attention to.  A user who likes
    to keep up with things should enjoy watching our logging at the INFO
    level; it shouldn't be too low-level, but it should give enough
    information that it keeps them relatively interested at peak times.

  * WARNING:  Appropriate to tell a user when we're doing something that they
    really ought to pay attention to.  Users should see WARNING and think,
    "Hmm, should I tell the Limnoria developers about this?"  Later, they should
    decide not to, but it should give the user a moment to pause and think
    about what's actually happening with their bot.

  * ERROR:    Appropriate to tell a user when something has gone wrong.
    Uncaught exceptions are ERRORs.  Conditions that we absolutely want to
    hear about should be errors.  Things that should *scare* the user should
    be errors.

  * CRITICAL: Not really appropriate.  I can think of no absolutely critical
    issue yet encountered in Limnoria; the only possible thing I can imagine is
    to notify the user that the partition on which Limnoria is running has
    filled up.  That would be a CRITICAL condition, but it would also be hard
    to log :)


* All plugins should have test cases written for them.  Even if it doesn't
  actually test anything but just exists, it's good to have the test there so
  there's a place to add more tests later (and so we can be sure that all
  plugins are adequately documented; PluginTestCase checks that every command
  has documentation)

* SQL table names should be all-lowercase and include underscores to separate
  words.  This is because SQL itself is case-insensitive.  This doesn't
  change, however the fact that variable/member names should be camel case.

* SQL statements in code should put SQL words in ALL CAPS::

    """SELECT quote FROM quotes ORDER BY random() LIMIT 1"""

  This makes SQL significantly easier to read.

* Common variable names

  - L => an arbitrary list.

  - t => an arbitrary tuple.

  - x => an arbitrary float.

  - s => an arbitrary string.

  - f => an arbitrary function.

  - p => an arbitrary predicate.

  - i,n => an arbitrary integer.

  - cb => an arbitrary callback.

  - db => a database handle.

  - fd => a file-like object.

  - msg => an ircmsgs.IrcMsg object.

  - irc => an irclib.Irc object (or proxy)

  - nick => a string that is an IRC nick.

  - channel => a string that is an IRC channel.

  - hostmask => a string that is a user's IRC prefix.

  When the semantic functionality (that is, the "meaning" of a variable is
  obvious from context), one of these names should be used.  This just makes it
  easier for people reading our code to know what a variable represents
  without scouring the surrounding code.

* Multiple variable assignments should always be surrounded with parentheses
  -- i.e., if you're using the partition function, then your assignment
  statement should look like::

    (good, bad) = partition(p, L)

  The parentheses make it obvious that you're doing a multiple assignment, and
  that's important because I hate reading code and wondering where a variable
  came from.