"""Fixer for function definitions with tuple parameters.

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def func(((a, b), c), d):

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...

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->

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def func(x, d):

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((a, b), c) = x

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...

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It will also support lambdas:

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lambda (x, y): x + y -> lambda t: t[0] + t[1]

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# The parens are a syntax error in Python 3

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lambda (x): x + y -> lambda x: x + y

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"""

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# Author: Collin Winter

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# Local imports

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from .. import pytree

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from ..pgen2 import token

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from .. import fixer_base

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from ..fixer_util import Assign, Name, Newline, Number, Subscript, syms

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def is_docstring(stmt):

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return isinstance(stmt, pytree.Node) and \

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stmt.children[0].type == token.STRING

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class FixTupleParams(fixer_base.BaseFix):

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run_order = 4 #use a lower order since lambda is part of other

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#patterns

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BM_compatible = True

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PATTERN = """

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funcdef< 'def' any parameters< '(' args=any ')' >

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['->' any] ':' suite=any+ >

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|

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lambda=

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lambdef< 'lambda' args=vfpdef< '(' inner=any ')' >

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':' body=any

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>

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"""

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def transform(self, node, results):

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if "lambda" in results:

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return self.transform_lambda(node, results)

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new_lines = []

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suite = results["suite"]

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args = results["args"]

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# This crap is so "def foo(...): x = 5; y = 7" is handled correctly.

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# TODO(cwinter): suite-cleanup

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if suite[0].children[1].type == token.INDENT:

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start = 2

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indent = suite[0].children[1].value

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end = Newline()

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else:

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start = 0

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indent = u"; "

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end = pytree.Leaf(token.INDENT, u"")

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# We need access to self for new_name(), and making this a method

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# doesn't feel right. Closing over self and new_lines makes the

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# code below cleaner.

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def handle_tuple(tuple_arg, add_prefix=False):

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n = Name(self.new_name())

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arg = tuple_arg.clone()

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arg.prefix = u""

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stmt = Assign(arg, n.clone())

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if add_prefix:

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n.prefix = u" "

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tuple_arg.replace(n)

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new_lines.append(pytree.Node(syms.simple_stmt,

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[stmt, end.clone()]))

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if args.type == syms.tfpdef:

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handle_tuple(args)

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elif args.type == syms.typedargslist:

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for i, arg in enumerate(args.children):

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if arg.type == syms.tfpdef:

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# Without add_prefix, the emitted code is correct,

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# just ugly.

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handle_tuple(arg, add_prefix=(i > 0))

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if not new_lines:

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return

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# This isn't strictly necessary, but it plays nicely with other fixers.

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# TODO(cwinter) get rid of this when children becomes a smart list

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for line in new_lines:

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line.parent = suite[0]

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# TODO(cwinter) suite-cleanup

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after = start

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if start == 0:

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new_lines[0].prefix = u" "

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elif is_docstring(suite[0].children[start]):

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new_lines[0].prefix = indent

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after = start + 1

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for line in new_lines:

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line.parent = suite[0]

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suite[0].children[after:after] = new_lines

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for i in range(after+1, after+len(new_lines)+1):

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suite[0].children[i].prefix = indent

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suite[0].changed()

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def transform_lambda(self, node, results):

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args = results["args"]

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body = results["body"]

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inner = simplify_args(results["inner"])

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# Replace lambda ((((x)))): x with lambda x: x

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if inner.type == token.NAME:

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inner = inner.clone()

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inner.prefix = u" "

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args.replace(inner)

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return

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params = find_params(args)

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to_index = map_to_index(params)

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tup_name = self.new_name(tuple_name(params))

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new_param = Name(tup_name, prefix=u" ")

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args.replace(new_param.clone())

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for n in body.post_order():

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if n.type == token.NAME and n.value in to_index:

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subscripts = [c.clone() for c in to_index[n.value]]

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new = pytree.Node(syms.power,

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[new_param.clone()] + subscripts)

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new.prefix = n.prefix

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n.replace(new)

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### Helper functions for transform_lambda()

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def simplify_args(node):

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if node.type in (syms.vfplist, token.NAME):

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return node

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elif node.type == syms.vfpdef:

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# These look like vfpdef< '(' x ')' > where x is NAME

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# or another vfpdef instance (leading to recursion).

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while node.type == syms.vfpdef:

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node = node.children[1]

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return node

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raise RuntimeError("Received unexpected node %s" % node)

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def find_params(node):

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if node.type == syms.vfpdef:

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return find_params(node.children[1])

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elif node.type == token.NAME:

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return node.value

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return [find_params(c) for c in node.children if c.type != token.COMMA]

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def map_to_index(param_list, prefix=[], d=None):

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if d is None:

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d = {}

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for i, obj in enumerate(param_list):

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trailer = [Subscript(Number(unicode(i)))]

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if isinstance(obj, list):

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map_to_index(obj, trailer, d=d)

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else:

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d[obj] = prefix + trailer

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return d

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def tuple_name(param_list):

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l = []

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for obj in param_list:

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if isinstance(obj, list):

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l.append(tuple_name(obj))

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else:

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l.append(obj)

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return u"_".join(l)

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