CODINGSTYLE

C

The C implementations should follow the kernel/git coding style.

Python

Python code follows PEP8 with regard to coding style and PEP257 with regard to docstring style. Multi-line docstrings should have one short summary line, followed by a blank line and a series of paragraphs. The last paragraph should be followed by a line that closes the docstring (no blank line in between). Here's an example from lib/bup/helpers.py:

def unlink(f):
    """Delete a file at path 'f' if it currently exists.

    Unlike os.unlink(), does not throw an exception if the file didn't already
    exist.
    """
    ...

Module-level docstrings follow exactly the same guidelines but without the blank line between the summary and the details.

Exception Handling

Avoid finally: blocks in favor of explict catches because a throw from a finally block will lose any pending exception. An explicit catch can chain it (see below).

To behave similarly under Python 2 and 3, use add_ex_tb() to explicitly add stack traces to any exceptions that are going to be re-raised by anything other than a no-argument raise (otherwise the stack trace will be lost):

try:
    ...
except ... as ex:
    add_ex_tb(ex)
    pending_ex = ex
...
raise pending_ex

If an exception is thrown from an exception handler, the pending exception should be "chained" to the new exception as the context. This can be accomplished via chain_ex():

try:
    ...
except ... as ex:
    add_ex_tb(ex)
    try:
        ...
    except ... as ex2:
        add_ex_tb(ex2)
        raise chain_ex(ex2, ex)

See the end of lib/bup/compat.py for a functional example.