Viewing file:  fix_kwargs.py (5.85 KB) -rw-r--r--
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u"""
Fixer for Python 3 function parameter syntax
This fixer is rather sensitive to incorrect py3k syntax.
"""
# Note: "relevant" parameters are parameters following the first STAR in the list.
from lib2to3 import fixer_base
from lib2to3.fixer_util import token, String, Newline, Comma, Name
from libfuturize.fixer_util import indentation, suitify, DoubleStar
_assign_template = u"%(name)s = %(kwargs)s['%(name)s']; del %(kwargs)s['%(name)s']"
_if_template = u"if '%(name)s' in %(kwargs)s: %(assign)s"
_else_template = u"else: %(name)s = %(default)s"
_kwargs_default_name = u"_3to2kwargs"
def gen_params(raw_params):
u"""
Generator that yields tuples of (name, default_value) for each parameter in the list
If no default is given, then it is default_value is None (not Leaf(token.NAME, 'None'))
"""
assert raw_params[0].type == token.STAR and len(raw_params) > 2
curr_idx = 2 # the first place a keyword-only parameter name can be is index 2
max_idx = len(raw_params)
while curr_idx < max_idx:
curr_item = raw_params[curr_idx]
prev_item = curr_item.prev_sibling
if curr_item.type != token.NAME:
curr_idx += 1
continue
if prev_item is not None and prev_item.type == token.DOUBLESTAR:
break
name = curr_item.value
nxt = curr_item.next_sibling
if nxt is not None and nxt.type == token.EQUAL:
default_value = nxt.next_sibling
curr_idx += 2
else:
default_value = None
yield (name, default_value)
curr_idx += 1
def remove_params(raw_params, kwargs_default=_kwargs_default_name):
u"""
Removes all keyword-only args from the params list and a bare star, if any.
Does not add the kwargs dict if needed.
Returns True if more action is needed, False if not
(more action is needed if no kwargs dict exists)
"""
assert raw_params[0].type == token.STAR
if raw_params[1].type == token.COMMA:
raw_params[0].remove()
raw_params[1].remove()
kw_params = raw_params[2:]
else:
kw_params = raw_params[3:]
for param in kw_params:
if param.type != token.DOUBLESTAR:
param.remove()
else:
return False
else:
return True
def needs_fixing(raw_params, kwargs_default=_kwargs_default_name):
u"""
Returns string with the name of the kwargs dict if the params after the first star need fixing
Otherwise returns empty string
"""
found_kwargs = False
needs_fix = False
for t in raw_params[2:]:
if t.type == token.COMMA:
# Commas are irrelevant at this stage.
continue
elif t.type == token.NAME and not found_kwargs:
# Keyword-only argument: definitely need to fix.
needs_fix = True
elif t.type == token.NAME and found_kwargs:
# Return 'foobar' of **foobar, if needed.
return t.value if needs_fix else u''
elif t.type == token.DOUBLESTAR:
# Found either '*' from **foobar.
found_kwargs = True
else:
# Never found **foobar. Return a synthetic name, if needed.
return kwargs_default if needs_fix else u''
class FixKwargs(fixer_base.BaseFix):
run_order = 7 # Run after function annotations are removed
PATTERN = u"funcdef< 'def' NAME parameters< '(' arglist=typedargslist< params=any* > ')' > ':' suite=any >"
def transform(self, node, results):
params_rawlist = results[u"params"]
for i, item in enumerate(params_rawlist):
if item.type == token.STAR:
params_rawlist = params_rawlist[i:]
break
else:
return
# params is guaranteed to be a list starting with *.
# if fixing is needed, there will be at least 3 items in this list:
# [STAR, COMMA, NAME] is the minimum that we need to worry about.
new_kwargs = needs_fixing(params_rawlist)
# new_kwargs is the name of the kwargs dictionary.
if not new_kwargs:
return
suitify(node)
# At this point, params_rawlist is guaranteed to be a list
# beginning with a star that includes at least one keyword-only param
# e.g., [STAR, NAME, COMMA, NAME, COMMA, DOUBLESTAR, NAME] or
# [STAR, COMMA, NAME], or [STAR, COMMA, NAME, COMMA, DOUBLESTAR, NAME]
# Anatomy of a funcdef: ['def', 'name', parameters, ':', suite]
# Anatomy of that suite: [NEWLINE, INDENT, first_stmt, all_other_stmts]
# We need to insert our new stuff before the first_stmt and change the
# first_stmt's prefix.
suite = node.children[4]
first_stmt = suite.children[2]
ident = indentation(first_stmt)
for name, default_value in gen_params(params_rawlist):
if default_value is None:
suite.insert_child(2, Newline())
suite.insert_child(2, String(_assign_template %{u'name':name, u'kwargs':new_kwargs}, prefix=ident))
else:
suite.insert_child(2, Newline())
suite.insert_child(2, String(_else_template %{u'name':name, u'default':default_value}, prefix=ident))
suite.insert_child(2, Newline())
suite.insert_child(2, String(_if_template %{u'assign':_assign_template %{u'name':name, u'kwargs':new_kwargs}, u'name':name, u'kwargs':new_kwargs}, prefix=ident))
first_stmt.prefix = ident
suite.children[2].prefix = u""
# Now, we need to fix up the list of params.
must_add_kwargs = remove_params(params_rawlist)
if must_add_kwargs:
arglist = results[u'arglist']
if len(arglist.children) > 0 and arglist.children[-1].type != token.COMMA:
arglist.append_child(Comma())
arglist.append_child(DoubleStar(prefix=u" "))
arglist.append_child(Name(new_kwargs))
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