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vim: Parse skip_magic_trailing_comma from pyproject.toml (#2613)
[etc/vim.git] / src / blib2to3 / pgen2 / pgen.py
1 # Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
2 # Licensed to PSF under a Contributor Agreement.
3
4 # Pgen imports
5 from . import grammar, token, tokenize
6
7 from typing import (
8     Any,
9     Dict,
10     IO,
11     Iterator,
12     List,
13     Optional,
14     Text,
15     Tuple,
16     Union,
17     Sequence,
18     NoReturn,
19 )
20 from blib2to3.pgen2 import grammar
21 from blib2to3.pgen2.tokenize import GoodTokenInfo
22 import os
23
24
25 Path = Union[str, "os.PathLike[str]"]
26
27
28 class PgenGrammar(grammar.Grammar):
29     pass
30
31
32 class ParserGenerator(object):
33
34     filename: Path
35     stream: IO[Text]
36     generator: Iterator[GoodTokenInfo]
37     first: Dict[Text, Optional[Dict[Text, int]]]
38
39     def __init__(self, filename: Path, stream: Optional[IO[Text]] = None) -> None:
40         close_stream = None
41         if stream is None:
42             stream = open(filename)
43             close_stream = stream.close
44         self.filename = filename
45         self.stream = stream
46         self.generator = tokenize.generate_tokens(stream.readline)
47         self.gettoken()  # Initialize lookahead
48         self.dfas, self.startsymbol = self.parse()
49         if close_stream is not None:
50             close_stream()
51         self.first = {}  # map from symbol name to set of tokens
52         self.addfirstsets()
53
54     def make_grammar(self) -> PgenGrammar:
55         c = PgenGrammar()
56         names = list(self.dfas.keys())
57         names.sort()
58         names.remove(self.startsymbol)
59         names.insert(0, self.startsymbol)
60         for name in names:
61             i = 256 + len(c.symbol2number)
62             c.symbol2number[name] = i
63             c.number2symbol[i] = name
64         for name in names:
65             dfa = self.dfas[name]
66             states = []
67             for state in dfa:
68                 arcs = []
69                 for label, next in sorted(state.arcs.items()):
70                     arcs.append((self.make_label(c, label), dfa.index(next)))
71                 if state.isfinal:
72                     arcs.append((0, dfa.index(state)))
73                 states.append(arcs)
74             c.states.append(states)
75             c.dfas[c.symbol2number[name]] = (states, self.make_first(c, name))
76         c.start = c.symbol2number[self.startsymbol]
77         return c
78
79     def make_first(self, c: PgenGrammar, name: Text) -> Dict[int, int]:
80         rawfirst = self.first[name]
81         assert rawfirst is not None
82         first = {}
83         for label in sorted(rawfirst):
84             ilabel = self.make_label(c, label)
85             ##assert ilabel not in first # XXX failed on <> ... !=
86             first[ilabel] = 1
87         return first
88
89     def make_label(self, c: PgenGrammar, label: Text) -> int:
90         # XXX Maybe this should be a method on a subclass of converter?
91         ilabel = len(c.labels)
92         if label[0].isalpha():
93             # Either a symbol name or a named token
94             if label in c.symbol2number:
95                 # A symbol name (a non-terminal)
96                 if label in c.symbol2label:
97                     return c.symbol2label[label]
98                 else:
99                     c.labels.append((c.symbol2number[label], None))
100                     c.symbol2label[label] = ilabel
101                     return ilabel
102             else:
103                 # A named token (NAME, NUMBER, STRING)
104                 itoken = getattr(token, label, None)
105                 assert isinstance(itoken, int), label
106                 assert itoken in token.tok_name, label
107                 if itoken in c.tokens:
108                     return c.tokens[itoken]
109                 else:
110                     c.labels.append((itoken, None))
111                     c.tokens[itoken] = ilabel
112                     return ilabel
113         else:
114             # Either a keyword or an operator
115             assert label[0] in ('"', "'"), label
116             value = eval(label)
117             if value[0].isalpha():
118                 if label[0] == '"':
119                     keywords = c.soft_keywords
120                 else:
121                     keywords = c.keywords
122
123                 # A keyword
124                 if value in keywords:
125                     return keywords[value]
126                 else:
127                     c.labels.append((token.NAME, value))
128                     keywords[value] = ilabel
129                     return ilabel
130             else:
131                 # An operator (any non-numeric token)
132                 itoken = grammar.opmap[value]  # Fails if unknown token
133                 if itoken in c.tokens:
134                     return c.tokens[itoken]
135                 else:
136                     c.labels.append((itoken, None))
137                     c.tokens[itoken] = ilabel
138                     return ilabel
139
140     def addfirstsets(self) -> None:
141         names = list(self.dfas.keys())
142         names.sort()
143         for name in names:
144             if name not in self.first:
145                 self.calcfirst(name)
146             # print name, self.first[name].keys()
147
148     def calcfirst(self, name: Text) -> None:
149         dfa = self.dfas[name]
150         self.first[name] = None  # dummy to detect left recursion
151         state = dfa[0]
152         totalset: Dict[str, int] = {}
153         overlapcheck = {}
154         for label, next in state.arcs.items():
155             if label in self.dfas:
156                 if label in self.first:
157                     fset = self.first[label]
158                     if fset is None:
159                         raise ValueError("recursion for rule %r" % name)
160                 else:
161                     self.calcfirst(label)
162                     fset = self.first[label]
163                     assert fset is not None
164                 totalset.update(fset)
165                 overlapcheck[label] = fset
166             else:
167                 totalset[label] = 1
168                 overlapcheck[label] = {label: 1}
169         inverse: Dict[str, str] = {}
170         for label, itsfirst in overlapcheck.items():
171             for symbol in itsfirst:
172                 if symbol in inverse:
173                     raise ValueError(
174                         "rule %s is ambiguous; %s is in the first sets of %s as well"
175                         " as %s" % (name, symbol, label, inverse[symbol])
176                     )
177                 inverse[symbol] = label
178         self.first[name] = totalset
179
180     def parse(self) -> Tuple[Dict[Text, List["DFAState"]], Text]:
181         dfas = {}
182         startsymbol: Optional[str] = None
183         # MSTART: (NEWLINE | RULE)* ENDMARKER
184         while self.type != token.ENDMARKER:
185             while self.type == token.NEWLINE:
186                 self.gettoken()
187             # RULE: NAME ':' RHS NEWLINE
188             name = self.expect(token.NAME)
189             self.expect(token.OP, ":")
190             a, z = self.parse_rhs()
191             self.expect(token.NEWLINE)
192             # self.dump_nfa(name, a, z)
193             dfa = self.make_dfa(a, z)
194             # self.dump_dfa(name, dfa)
195             oldlen = len(dfa)
196             self.simplify_dfa(dfa)
197             newlen = len(dfa)
198             dfas[name] = dfa
199             # print name, oldlen, newlen
200             if startsymbol is None:
201                 startsymbol = name
202         assert startsymbol is not None
203         return dfas, startsymbol
204
205     def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
206         # To turn an NFA into a DFA, we define the states of the DFA
207         # to correspond to *sets* of states of the NFA.  Then do some
208         # state reduction.  Let's represent sets as dicts with 1 for
209         # values.
210         assert isinstance(start, NFAState)
211         assert isinstance(finish, NFAState)
212
213         def closure(state: NFAState) -> Dict[NFAState, int]:
214             base: Dict[NFAState, int] = {}
215             addclosure(state, base)
216             return base
217
218         def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
219             assert isinstance(state, NFAState)
220             if state in base:
221                 return
222             base[state] = 1
223             for label, next in state.arcs:
224                 if label is None:
225                     addclosure(next, base)
226
227         states = [DFAState(closure(start), finish)]
228         for state in states:  # NB states grows while we're iterating
229             arcs: Dict[str, Dict[NFAState, int]] = {}
230             for nfastate in state.nfaset:
231                 for label, next in nfastate.arcs:
232                     if label is not None:
233                         addclosure(next, arcs.setdefault(label, {}))
234             for label, nfaset in sorted(arcs.items()):
235                 for st in states:
236                     if st.nfaset == nfaset:
237                         break
238                 else:
239                     st = DFAState(nfaset, finish)
240                     states.append(st)
241                 state.addarc(st, label)
242         return states  # List of DFAState instances; first one is start
243
244     def dump_nfa(self, name: Text, start: "NFAState", finish: "NFAState") -> None:
245         print("Dump of NFA for", name)
246         todo = [start]
247         for i, state in enumerate(todo):
248             print("  State", i, state is finish and "(final)" or "")
249             for label, next in state.arcs:
250                 if next in todo:
251                     j = todo.index(next)
252                 else:
253                     j = len(todo)
254                     todo.append(next)
255                 if label is None:
256                     print("    -> %d" % j)
257                 else:
258                     print("    %s -> %d" % (label, j))
259
260     def dump_dfa(self, name: Text, dfa: Sequence["DFAState"]) -> None:
261         print("Dump of DFA for", name)
262         for i, state in enumerate(dfa):
263             print("  State", i, state.isfinal and "(final)" or "")
264             for label, next in sorted(state.arcs.items()):
265                 print("    %s -> %d" % (label, dfa.index(next)))
266
267     def simplify_dfa(self, dfa: List["DFAState"]) -> None:
268         # This is not theoretically optimal, but works well enough.
269         # Algorithm: repeatedly look for two states that have the same
270         # set of arcs (same labels pointing to the same nodes) and
271         # unify them, until things stop changing.
272
273         # dfa is a list of DFAState instances
274         changes = True
275         while changes:
276             changes = False
277             for i, state_i in enumerate(dfa):
278                 for j in range(i + 1, len(dfa)):
279                     state_j = dfa[j]
280                     if state_i == state_j:
281                         # print "  unify", i, j
282                         del dfa[j]
283                         for state in dfa:
284                             state.unifystate(state_j, state_i)
285                         changes = True
286                         break
287
288     def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
289         # RHS: ALT ('|' ALT)*
290         a, z = self.parse_alt()
291         if self.value != "|":
292             return a, z
293         else:
294             aa = NFAState()
295             zz = NFAState()
296             aa.addarc(a)
297             z.addarc(zz)
298             while self.value == "|":
299                 self.gettoken()
300                 a, z = self.parse_alt()
301                 aa.addarc(a)
302                 z.addarc(zz)
303             return aa, zz
304
305     def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
306         # ALT: ITEM+
307         a, b = self.parse_item()
308         while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
309             c, d = self.parse_item()
310             b.addarc(c)
311             b = d
312         return a, b
313
314     def parse_item(self) -> Tuple["NFAState", "NFAState"]:
315         # ITEM: '[' RHS ']' | ATOM ['+' | '*']
316         if self.value == "[":
317             self.gettoken()
318             a, z = self.parse_rhs()
319             self.expect(token.OP, "]")
320             a.addarc(z)
321             return a, z
322         else:
323             a, z = self.parse_atom()
324             value = self.value
325             if value not in ("+", "*"):
326                 return a, z
327             self.gettoken()
328             z.addarc(a)
329             if value == "+":
330                 return a, z
331             else:
332                 return a, a
333
334     def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
335         # ATOM: '(' RHS ')' | NAME | STRING
336         if self.value == "(":
337             self.gettoken()
338             a, z = self.parse_rhs()
339             self.expect(token.OP, ")")
340             return a, z
341         elif self.type in (token.NAME, token.STRING):
342             a = NFAState()
343             z = NFAState()
344             a.addarc(z, self.value)
345             self.gettoken()
346             return a, z
347         else:
348             self.raise_error(
349                 "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
350             )
351             assert False
352
353     def expect(self, type: int, value: Optional[Any] = None) -> Text:
354         if self.type != type or (value is not None and self.value != value):
355             self.raise_error(
356                 "expected %s/%s, got %s/%s", type, value, self.type, self.value
357             )
358         value = self.value
359         self.gettoken()
360         return value
361
362     def gettoken(self) -> None:
363         tup = next(self.generator)
364         while tup[0] in (tokenize.COMMENT, tokenize.NL):
365             tup = next(self.generator)
366         self.type, self.value, self.begin, self.end, self.line = tup
367         # print token.tok_name[self.type], repr(self.value)
368
369     def raise_error(self, msg: str, *args: Any) -> NoReturn:
370         if args:
371             try:
372                 msg = msg % args
373             except:
374                 msg = " ".join([msg] + list(map(str, args)))
375         raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
376
377
378 class NFAState(object):
379     arcs: List[Tuple[Optional[Text], "NFAState"]]
380
381     def __init__(self) -> None:
382         self.arcs = []  # list of (label, NFAState) pairs
383
384     def addarc(self, next: "NFAState", label: Optional[Text] = None) -> None:
385         assert label is None or isinstance(label, str)
386         assert isinstance(next, NFAState)
387         self.arcs.append((label, next))
388
389
390 class DFAState(object):
391     nfaset: Dict[NFAState, Any]
392     isfinal: bool
393     arcs: Dict[Text, "DFAState"]
394
395     def __init__(self, nfaset: Dict[NFAState, Any], final: NFAState) -> None:
396         assert isinstance(nfaset, dict)
397         assert isinstance(next(iter(nfaset)), NFAState)
398         assert isinstance(final, NFAState)
399         self.nfaset = nfaset
400         self.isfinal = final in nfaset
401         self.arcs = {}  # map from label to DFAState
402
403     def addarc(self, next: "DFAState", label: Text) -> None:
404         assert isinstance(label, str)
405         assert label not in self.arcs
406         assert isinstance(next, DFAState)
407         self.arcs[label] = next
408
409     def unifystate(self, old: "DFAState", new: "DFAState") -> None:
410         for label, next in self.arcs.items():
411             if next is old:
412                 self.arcs[label] = new
413
414     def __eq__(self, other: Any) -> bool:
415         # Equality test -- ignore the nfaset instance variable
416         assert isinstance(other, DFAState)
417         if self.isfinal != other.isfinal:
418             return False
419         # Can't just return self.arcs == other.arcs, because that
420         # would invoke this method recursively, with cycles...
421         if len(self.arcs) != len(other.arcs):
422             return False
423         for label, next in self.arcs.items():
424             if next is not other.arcs.get(label):
425                 return False
426         return True
427
428     __hash__: Any = None  # For Py3 compatibility.
429
430
431 def generate_grammar(filename: Path = "Grammar.txt") -> PgenGrammar:
432     p = ParserGenerator(filename)
433     return p.make_grammar()