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[etc/vim.git] / src / black / brackets.py
1 """Builds on top of nodes.py to track brackets."""
2
3 from dataclasses import dataclass, field
4 import sys
5 from typing import Dict, Iterable, List, Optional, Tuple, Union
6
7 if sys.version_info < (3, 8):
8     from typing_extensions import Final
9 else:
10     from typing import Final
11
12 from blib2to3.pytree import Leaf, Node
13 from blib2to3.pgen2 import token
14
15 from black.nodes import syms, is_vararg, VARARGS_PARENTS, UNPACKING_PARENTS
16 from black.nodes import BRACKET, OPENING_BRACKETS, CLOSING_BRACKETS
17 from black.nodes import MATH_OPERATORS, COMPARATORS, LOGIC_OPERATORS
18
19 # types
20 LN = Union[Leaf, Node]
21 Depth = int
22 LeafID = int
23 NodeType = int
24 Priority = int
25
26
27 COMPREHENSION_PRIORITY: Final = 20
28 COMMA_PRIORITY: Final = 18
29 TERNARY_PRIORITY: Final = 16
30 LOGIC_PRIORITY: Final = 14
31 STRING_PRIORITY: Final = 12
32 COMPARATOR_PRIORITY: Final = 10
33 MATH_PRIORITIES: Final = {
34     token.VBAR: 9,
35     token.CIRCUMFLEX: 8,
36     token.AMPER: 7,
37     token.LEFTSHIFT: 6,
38     token.RIGHTSHIFT: 6,
39     token.PLUS: 5,
40     token.MINUS: 5,
41     token.STAR: 4,
42     token.SLASH: 4,
43     token.DOUBLESLASH: 4,
44     token.PERCENT: 4,
45     token.AT: 4,
46     token.TILDE: 3,
47     token.DOUBLESTAR: 2,
48 }
49 DOT_PRIORITY: Final = 1
50
51
52 class BracketMatchError(Exception):
53     """Raised when an opening bracket is unable to be matched to a closing bracket."""
54
55
56 @dataclass
57 class BracketTracker:
58     """Keeps track of brackets on a line."""
59
60     depth: int = 0
61     bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = field(default_factory=dict)
62     delimiters: Dict[LeafID, Priority] = field(default_factory=dict)
63     previous: Optional[Leaf] = None
64     _for_loop_depths: List[int] = field(default_factory=list)
65     _lambda_argument_depths: List[int] = field(default_factory=list)
66     invisible: List[Leaf] = field(default_factory=list)
67
68     def mark(self, leaf: Leaf) -> None:
69         """Mark `leaf` with bracket-related metadata. Keep track of delimiters.
70
71         All leaves receive an int `bracket_depth` field that stores how deep
72         within brackets a given leaf is. 0 means there are no enclosing brackets
73         that started on this line.
74
75         If a leaf is itself a closing bracket, it receives an `opening_bracket`
76         field that it forms a pair with. This is a one-directional link to
77         avoid reference cycles.
78
79         If a leaf is a delimiter (a token on which Black can split the line if
80         needed) and it's on depth 0, its `id()` is stored in the tracker's
81         `delimiters` field.
82         """
83         if leaf.type == token.COMMENT:
84             return
85
86         self.maybe_decrement_after_for_loop_variable(leaf)
87         self.maybe_decrement_after_lambda_arguments(leaf)
88         if leaf.type in CLOSING_BRACKETS:
89             self.depth -= 1
90             try:
91                 opening_bracket = self.bracket_match.pop((self.depth, leaf.type))
92             except KeyError as e:
93                 raise BracketMatchError(
94                     "Unable to match a closing bracket to the following opening"
95                     f" bracket: {leaf}"
96                 ) from e
97             leaf.opening_bracket = opening_bracket
98             if not leaf.value:
99                 self.invisible.append(leaf)
100         leaf.bracket_depth = self.depth
101         if self.depth == 0:
102             delim = is_split_before_delimiter(leaf, self.previous)
103             if delim and self.previous is not None:
104                 self.delimiters[id(self.previous)] = delim
105             else:
106                 delim = is_split_after_delimiter(leaf, self.previous)
107                 if delim:
108                     self.delimiters[id(leaf)] = delim
109         if leaf.type in OPENING_BRACKETS:
110             self.bracket_match[self.depth, BRACKET[leaf.type]] = leaf
111             self.depth += 1
112             if not leaf.value:
113                 self.invisible.append(leaf)
114         self.previous = leaf
115         self.maybe_increment_lambda_arguments(leaf)
116         self.maybe_increment_for_loop_variable(leaf)
117
118     def any_open_brackets(self) -> bool:
119         """Return True if there is an yet unmatched open bracket on the line."""
120         return bool(self.bracket_match)
121
122     def max_delimiter_priority(self, exclude: Iterable[LeafID] = ()) -> Priority:
123         """Return the highest priority of a delimiter found on the line.
124
125         Values are consistent with what `is_split_*_delimiter()` return.
126         Raises ValueError on no delimiters.
127         """
128         return max(v for k, v in self.delimiters.items() if k not in exclude)
129
130     def delimiter_count_with_priority(self, priority: Priority = 0) -> int:
131         """Return the number of delimiters with the given `priority`.
132
133         If no `priority` is passed, defaults to max priority on the line.
134         """
135         if not self.delimiters:
136             return 0
137
138         priority = priority or self.max_delimiter_priority()
139         return sum(1 for p in self.delimiters.values() if p == priority)
140
141     def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool:
142         """In a for loop, or comprehension, the variables are often unpacks.
143
144         To avoid splitting on the comma in this situation, increase the depth of
145         tokens between `for` and `in`.
146         """
147         if leaf.type == token.NAME and leaf.value == "for":
148             self.depth += 1
149             self._for_loop_depths.append(self.depth)
150             return True
151
152         return False
153
154     def maybe_decrement_after_for_loop_variable(self, leaf: Leaf) -> bool:
155         """See `maybe_increment_for_loop_variable` above for explanation."""
156         if (
157             self._for_loop_depths
158             and self._for_loop_depths[-1] == self.depth
159             and leaf.type == token.NAME
160             and leaf.value == "in"
161         ):
162             self.depth -= 1
163             self._for_loop_depths.pop()
164             return True
165
166         return False
167
168     def maybe_increment_lambda_arguments(self, leaf: Leaf) -> bool:
169         """In a lambda expression, there might be more than one argument.
170
171         To avoid splitting on the comma in this situation, increase the depth of
172         tokens between `lambda` and `:`.
173         """
174         if leaf.type == token.NAME and leaf.value == "lambda":
175             self.depth += 1
176             self._lambda_argument_depths.append(self.depth)
177             return True
178
179         return False
180
181     def maybe_decrement_after_lambda_arguments(self, leaf: Leaf) -> bool:
182         """See `maybe_increment_lambda_arguments` above for explanation."""
183         if (
184             self._lambda_argument_depths
185             and self._lambda_argument_depths[-1] == self.depth
186             and leaf.type == token.COLON
187         ):
188             self.depth -= 1
189             self._lambda_argument_depths.pop()
190             return True
191
192         return False
193
194     def get_open_lsqb(self) -> Optional[Leaf]:
195         """Return the most recent opening square bracket (if any)."""
196         return self.bracket_match.get((self.depth - 1, token.RSQB))
197
198
199 def is_split_after_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
200     """Return the priority of the `leaf` delimiter, given a line break after it.
201
202     The delimiter priorities returned here are from those delimiters that would
203     cause a line break after themselves.
204
205     Higher numbers are higher priority.
206     """
207     if leaf.type == token.COMMA:
208         return COMMA_PRIORITY
209
210     return 0
211
212
213 def is_split_before_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
214     """Return the priority of the `leaf` delimiter, given a line break before it.
215
216     The delimiter priorities returned here are from those delimiters that would
217     cause a line break before themselves.
218
219     Higher numbers are higher priority.
220     """
221     if is_vararg(leaf, within=VARARGS_PARENTS | UNPACKING_PARENTS):
222         # * and ** might also be MATH_OPERATORS but in this case they are not.
223         # Don't treat them as a delimiter.
224         return 0
225
226     if (
227         leaf.type == token.DOT
228         and leaf.parent
229         and leaf.parent.type not in {syms.import_from, syms.dotted_name}
230         and (previous is None or previous.type in CLOSING_BRACKETS)
231     ):
232         return DOT_PRIORITY
233
234     if (
235         leaf.type in MATH_OPERATORS
236         and leaf.parent
237         and leaf.parent.type not in {syms.factor, syms.star_expr}
238     ):
239         return MATH_PRIORITIES[leaf.type]
240
241     if leaf.type in COMPARATORS:
242         return COMPARATOR_PRIORITY
243
244     if (
245         leaf.type == token.STRING
246         and previous is not None
247         and previous.type == token.STRING
248     ):
249         return STRING_PRIORITY
250
251     if leaf.type not in {token.NAME, token.ASYNC}:
252         return 0
253
254     if (
255         leaf.value == "for"
256         and leaf.parent
257         and leaf.parent.type in {syms.comp_for, syms.old_comp_for}
258         or leaf.type == token.ASYNC
259     ):
260         if (
261             not isinstance(leaf.prev_sibling, Leaf)
262             or leaf.prev_sibling.value != "async"
263         ):
264             return COMPREHENSION_PRIORITY
265
266     if (
267         leaf.value == "if"
268         and leaf.parent
269         and leaf.parent.type in {syms.comp_if, syms.old_comp_if}
270     ):
271         return COMPREHENSION_PRIORITY
272
273     if leaf.value in {"if", "else"} and leaf.parent and leaf.parent.type == syms.test:
274         return TERNARY_PRIORITY
275
276     if leaf.value == "is":
277         return COMPARATOR_PRIORITY
278
279     if (
280         leaf.value == "in"
281         and leaf.parent
282         and leaf.parent.type in {syms.comp_op, syms.comparison}
283         and not (
284             previous is not None
285             and previous.type == token.NAME
286             and previous.value == "not"
287         )
288     ):
289         return COMPARATOR_PRIORITY
290
291     if (
292         leaf.value == "not"
293         and leaf.parent
294         and leaf.parent.type == syms.comp_op
295         and not (
296             previous is not None
297             and previous.type == token.NAME
298             and previous.value == "is"
299         )
300     ):
301         return COMPARATOR_PRIORITY
302
303     if leaf.value in LOGIC_OPERATORS and leaf.parent:
304         return LOGIC_PRIORITY
305
306     return 0
307
308
309 def max_delimiter_priority_in_atom(node: LN) -> Priority:
310     """Return maximum delimiter priority inside `node`.
311
312     This is specific to atoms with contents contained in a pair of parentheses.
313     If `node` isn't an atom or there are no enclosing parentheses, returns 0.
314     """
315     if node.type != syms.atom:
316         return 0
317
318     first = node.children[0]
319     last = node.children[-1]
320     if not (first.type == token.LPAR and last.type == token.RPAR):
321         return 0
322
323     bt = BracketTracker()
324     for c in node.children[1:-1]:
325         if isinstance(c, Leaf):
326             bt.mark(c)
327         else:
328             for leaf in c.leaves():
329                 bt.mark(leaf)
330     try:
331         return bt.max_delimiter_priority()
332
333     except ValueError:
334         return 0