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1"""Fixer for function definitions with tuple parameters.
2
3def func(((a, b), c), d):
4    ...
5
6    ->
7
8def func(x, d):
9    ((a, b), c) = x
10    ...
11
12It will also support lambdas:
13
14    lambda (x, y): x + y -> lambda t: t[0] + t[1]
15
16    # The parens are a syntax error in Python 3
17    lambda (x): x + y -> lambda x: x + y
18"""
19# Author: Collin Winter
20
21# Local imports
22from .. import pytree
23from ..pgen2 import token
24from .. import fixer_base
25from ..fixer_util import Assign, Name, Newline, Number, Subscript, syms
26
27def is_docstring(stmt):
28    return isinstance(stmt, pytree.Node) and \
29           stmt.children[0].type == token.STRING
30
31class FixTupleParams(fixer_base.BaseFix):
32    run_order = 4 #use a lower order since lambda is part of other
33                  #patterns
34    BM_compatible = True
35
36    PATTERN = """
37              funcdef< 'def' any parameters< '(' args=any ')' >
38                       ['->' any] ':' suite=any+ >
39              |
40              lambda=
41              lambdef< 'lambda' args=vfpdef< '(' inner=any ')' >
42                       ':' body=any
43              >
44              """
45
46    def transform(self, node, results):
47        if "lambda" in results:
48            return self.transform_lambda(node, results)
49
50        new_lines = []
51        suite = results["suite"]
52        args = results["args"]
53        # This crap is so "def foo(...): x = 5; y = 7" is handled correctly.
54        # TODO(cwinter): suite-cleanup
55        if suite[0].children[1].type == token.INDENT:
56            start = 2
57            indent = suite[0].children[1].value
58            end = Newline()
59        else:
60            start = 0
61            indent = "; "
62            end = pytree.Leaf(token.INDENT, "")
63
64        # We need access to self for new_name(), and making this a method
65        #  doesn't feel right. Closing over self and new_lines makes the
66        #  code below cleaner.
67        def handle_tuple(tuple_arg, add_prefix=False):
68            n = Name(self.new_name())
69            arg = tuple_arg.clone()
70            arg.prefix = ""
71            stmt = Assign(arg, n.clone())
72            if add_prefix:
73                n.prefix = " "
74            tuple_arg.replace(n)
75            new_lines.append(pytree.Node(syms.simple_stmt,
76                                         [stmt, end.clone()]))
77
78        if args.type == syms.tfpdef:
79            handle_tuple(args)
80        elif args.type == syms.typedargslist:
81            for i, arg in enumerate(args.children):
82                if arg.type == syms.tfpdef:
83                    # Without add_prefix, the emitted code is correct,
84                    #  just ugly.
85                    handle_tuple(arg, add_prefix=(i > 0))
86
87        if not new_lines:
88            return
89
90        # This isn't strictly necessary, but it plays nicely with other fixers.
91        # TODO(cwinter) get rid of this when children becomes a smart list
92        for line in new_lines:
93            line.parent = suite[0]
94
95        # TODO(cwinter) suite-cleanup
96        after = start
97        if start == 0:
98            new_lines[0].prefix = " "
99        elif is_docstring(suite[0].children[start]):
100            new_lines[0].prefix = indent
101            after = start + 1
102
103        for line in new_lines:
104            line.parent = suite[0]
105        suite[0].children[after:after] = new_lines
106        for i in range(after+1, after+len(new_lines)+1):
107            suite[0].children[i].prefix = indent
108        suite[0].changed()
109
110    def transform_lambda(self, node, results):
111        args = results["args"]
112        body = results["body"]
113        inner = simplify_args(results["inner"])
114
115        # Replace lambda ((((x)))): x  with lambda x: x
116        if inner.type == token.NAME:
117            inner = inner.clone()
118            inner.prefix = " "
119            args.replace(inner)
120            return
121
122        params = find_params(args)
123        to_index = map_to_index(params)
124        tup_name = self.new_name(tuple_name(params))
125
126        new_param = Name(tup_name, prefix=" ")
127        args.replace(new_param.clone())
128        for n in body.post_order():
129            if n.type == token.NAME and n.value in to_index:
130                subscripts = [c.clone() for c in to_index[n.value]]
131                new = pytree.Node(syms.power,
132                                  [new_param.clone()] + subscripts)
133                new.prefix = n.prefix
134                n.replace(new)
135
136
137### Helper functions for transform_lambda()
138
139def simplify_args(node):
140    if node.type in (syms.vfplist, token.NAME):
141        return node
142    elif node.type == syms.vfpdef:
143        # These look like vfpdef< '(' x ')' > where x is NAME
144        # or another vfpdef instance (leading to recursion).
145        while node.type == syms.vfpdef:
146            node = node.children[1]
147        return node
148    raise RuntimeError("Received unexpected node %s" % node)
149
150def find_params(node):
151    if node.type == syms.vfpdef:
152        return find_params(node.children[1])
153    elif node.type == token.NAME:
154        return node.value
155    return [find_params(c) for c in node.children if c.type != token.COMMA]
156
157def map_to_index(param_list, prefix=[], d=None):
158    if d is None:
159        d = {}
160    for i, obj in enumerate(param_list):
161        trailer = [Subscript(Number(str(i)))]
162        if isinstance(obj, list):
163            map_to_index(obj, trailer, d=d)
164        else:
165            d[obj] = prefix + trailer
166    return d
167
168def tuple_name(param_list):
169    l = []
170    for obj in param_list:
171        if isinstance(obj, list):
172            l.append(tuple_name(obj))
173        else:
174            l.append(obj)
175    return "_".join(l)
176