0.6.2: Using argname to reimplement nameof (#44)

• Remove argument full for nameof, use vars_only instead. When vars_only=False, source of the argument returned.

  # before:
  nameof(a.b, full=True) # 'a.b'
  nameof(x[0], full=True) # unable to fetch
  # after (requires asttoken):
  nameof(a.b, vars_only=False) # 'a.b'
  nameof(x[0], vars_only=False) # 'x[0]'

• Add argument frame to argname, so that it can be wrapped.

  def argname2(arg, *more_args):
      return argname(arg, *more_args, frame=2)

• Allow argname to fetch the source of variable keyword arguments (**kwargs), which will be an empty dict ({}) when no keyword arguments passed.

  def func(a, **kwargs):
      return argname(a, kwargs)
  # before:
  func(x) # raises error
  # after:
  func(x) # returns ('x', {})

• Add argument pos_only to argname to only match the positional arguments

  # before
  def func(a, b=1):
    return argname(a)
  func(x) # 'x'
  func(x, b=2) # error since 2 is not ast.Name
  
  # after
  def func(a, b=1):
    return argname(a, pos_only=True)
  func(x) # 'x'
  func(x, b=2) # 'x'

• Parse the arguments only if needed

  # before
  def func(a, b):
    return argname(a)
  func(x, 1) # NonVariableArgumentError
  
  # after
  func(x, 1) # 'x'

• Allow variable positional arguments for argname so that argname(*args) is allowed

  # before
  def func(arg, *args):
    return argname(arg, args) # *args not allowed
  x = y = 1
  func(x, y) # ('x', ('y', 1))
  
  # after
  def func(arg, *args):
    return argname(arg, *args)
  x = y = 1
  func(x, y) # ('x', 'y')

• Add vars_only (defaults to False) argument to helpers.debug so source of expression becomes available

  a=1
  debug(a+a) # DEBUG: a+a=2