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Remove unused import statements using Pycln. (#2021)
[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                 # A keyword
119                 if value in c.keywords:
120                     return c.keywords[value]
121                 else:
122                     c.labels.append((token.NAME, value))
123                     c.keywords[value] = ilabel
124                     return ilabel
125             else:
126                 # An operator (any non-numeric token)
127                 itoken = grammar.opmap[value]  # Fails if unknown token
128                 if itoken in c.tokens:
129                     return c.tokens[itoken]
130                 else:
131                     c.labels.append((itoken, None))
132                     c.tokens[itoken] = ilabel
133                     return ilabel
134
135     def addfirstsets(self) -> None:
136         names = list(self.dfas.keys())
137         names.sort()
138         for name in names:
139             if name not in self.first:
140                 self.calcfirst(name)
141             # print name, self.first[name].keys()
142
143     def calcfirst(self, name: Text) -> None:
144         dfa = self.dfas[name]
145         self.first[name] = None  # dummy to detect left recursion
146         state = dfa[0]
147         totalset: Dict[str, int] = {}
148         overlapcheck = {}
149         for label, next in state.arcs.items():
150             if label in self.dfas:
151                 if label in self.first:
152                     fset = self.first[label]
153                     if fset is None:
154                         raise ValueError("recursion for rule %r" % name)
155                 else:
156                     self.calcfirst(label)
157                     fset = self.first[label]
158                     assert fset is not None
159                 totalset.update(fset)
160                 overlapcheck[label] = fset
161             else:
162                 totalset[label] = 1
163                 overlapcheck[label] = {label: 1}
164         inverse: Dict[str, str] = {}
165         for label, itsfirst in overlapcheck.items():
166             for symbol in itsfirst:
167                 if symbol in inverse:
168                     raise ValueError(
169                         "rule %s is ambiguous; %s is in the first sets of %s as well"
170                         " as %s" % (name, symbol, label, inverse[symbol])
171                     )
172                 inverse[symbol] = label
173         self.first[name] = totalset
174
175     def parse(self) -> Tuple[Dict[Text, List["DFAState"]], Text]:
176         dfas = {}
177         startsymbol: Optional[str] = None
178         # MSTART: (NEWLINE | RULE)* ENDMARKER
179         while self.type != token.ENDMARKER:
180             while self.type == token.NEWLINE:
181                 self.gettoken()
182             # RULE: NAME ':' RHS NEWLINE
183             name = self.expect(token.NAME)
184             self.expect(token.OP, ":")
185             a, z = self.parse_rhs()
186             self.expect(token.NEWLINE)
187             # self.dump_nfa(name, a, z)
188             dfa = self.make_dfa(a, z)
189             # self.dump_dfa(name, dfa)
190             oldlen = len(dfa)
191             self.simplify_dfa(dfa)
192             newlen = len(dfa)
193             dfas[name] = dfa
194             # print name, oldlen, newlen
195             if startsymbol is None:
196                 startsymbol = name
197         assert startsymbol is not None
198         return dfas, startsymbol
199
200     def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
201         # To turn an NFA into a DFA, we define the states of the DFA
202         # to correspond to *sets* of states of the NFA.  Then do some
203         # state reduction.  Let's represent sets as dicts with 1 for
204         # values.
205         assert isinstance(start, NFAState)
206         assert isinstance(finish, NFAState)
207
208         def closure(state: NFAState) -> Dict[NFAState, int]:
209             base: Dict[NFAState, int] = {}
210             addclosure(state, base)
211             return base
212
213         def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
214             assert isinstance(state, NFAState)
215             if state in base:
216                 return
217             base[state] = 1
218             for label, next in state.arcs:
219                 if label is None:
220                     addclosure(next, base)
221
222         states = [DFAState(closure(start), finish)]
223         for state in states:  # NB states grows while we're iterating
224             arcs: Dict[str, Dict[NFAState, int]] = {}
225             for nfastate in state.nfaset:
226                 for label, next in nfastate.arcs:
227                     if label is not None:
228                         addclosure(next, arcs.setdefault(label, {}))
229             for label, nfaset in sorted(arcs.items()):
230                 for st in states:
231                     if st.nfaset == nfaset:
232                         break
233                 else:
234                     st = DFAState(nfaset, finish)
235                     states.append(st)
236                 state.addarc(st, label)
237         return states  # List of DFAState instances; first one is start
238
239     def dump_nfa(self, name: Text, start: "NFAState", finish: "NFAState") -> None:
240         print("Dump of NFA for", name)
241         todo = [start]
242         for i, state in enumerate(todo):
243             print("  State", i, state is finish and "(final)" or "")
244             for label, next in state.arcs:
245                 if next in todo:
246                     j = todo.index(next)
247                 else:
248                     j = len(todo)
249                     todo.append(next)
250                 if label is None:
251                     print("    -> %d" % j)
252                 else:
253                     print("    %s -> %d" % (label, j))
254
255     def dump_dfa(self, name: Text, dfa: Sequence["DFAState"]) -> None:
256         print("Dump of DFA for", name)
257         for i, state in enumerate(dfa):
258             print("  State", i, state.isfinal and "(final)" or "")
259             for label, next in sorted(state.arcs.items()):
260                 print("    %s -> %d" % (label, dfa.index(next)))
261
262     def simplify_dfa(self, dfa: List["DFAState"]) -> None:
263         # This is not theoretically optimal, but works well enough.
264         # Algorithm: repeatedly look for two states that have the same
265         # set of arcs (same labels pointing to the same nodes) and
266         # unify them, until things stop changing.
267
268         # dfa is a list of DFAState instances
269         changes = True
270         while changes:
271             changes = False
272             for i, state_i in enumerate(dfa):
273                 for j in range(i + 1, len(dfa)):
274                     state_j = dfa[j]
275                     if state_i == state_j:
276                         # print "  unify", i, j
277                         del dfa[j]
278                         for state in dfa:
279                             state.unifystate(state_j, state_i)
280                         changes = True
281                         break
282
283     def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
284         # RHS: ALT ('|' ALT)*
285         a, z = self.parse_alt()
286         if self.value != "|":
287             return a, z
288         else:
289             aa = NFAState()
290             zz = NFAState()
291             aa.addarc(a)
292             z.addarc(zz)
293             while self.value == "|":
294                 self.gettoken()
295                 a, z = self.parse_alt()
296                 aa.addarc(a)
297                 z.addarc(zz)
298             return aa, zz
299
300     def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
301         # ALT: ITEM+
302         a, b = self.parse_item()
303         while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
304             c, d = self.parse_item()
305             b.addarc(c)
306             b = d
307         return a, b
308
309     def parse_item(self) -> Tuple["NFAState", "NFAState"]:
310         # ITEM: '[' RHS ']' | ATOM ['+' | '*']
311         if self.value == "[":
312             self.gettoken()
313             a, z = self.parse_rhs()
314             self.expect(token.OP, "]")
315             a.addarc(z)
316             return a, z
317         else:
318             a, z = self.parse_atom()
319             value = self.value
320             if value not in ("+", "*"):
321                 return a, z
322             self.gettoken()
323             z.addarc(a)
324             if value == "+":
325                 return a, z
326             else:
327                 return a, a
328
329     def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
330         # ATOM: '(' RHS ')' | NAME | STRING
331         if self.value == "(":
332             self.gettoken()
333             a, z = self.parse_rhs()
334             self.expect(token.OP, ")")
335             return a, z
336         elif self.type in (token.NAME, token.STRING):
337             a = NFAState()
338             z = NFAState()
339             a.addarc(z, self.value)
340             self.gettoken()
341             return a, z
342         else:
343             self.raise_error(
344                 "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
345             )
346             assert False
347
348     def expect(self, type: int, value: Optional[Any] = None) -> Text:
349         if self.type != type or (value is not None and self.value != value):
350             self.raise_error(
351                 "expected %s/%s, got %s/%s", type, value, self.type, self.value
352             )
353         value = self.value
354         self.gettoken()
355         return value
356
357     def gettoken(self) -> None:
358         tup = next(self.generator)
359         while tup[0] in (tokenize.COMMENT, tokenize.NL):
360             tup = next(self.generator)
361         self.type, self.value, self.begin, self.end, self.line = tup
362         # print token.tok_name[self.type], repr(self.value)
363
364     def raise_error(self, msg: str, *args: Any) -> NoReturn:
365         if args:
366             try:
367                 msg = msg % args
368             except:
369                 msg = " ".join([msg] + list(map(str, args)))
370         raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
371
372
373 class NFAState(object):
374     arcs: List[Tuple[Optional[Text], "NFAState"]]
375
376     def __init__(self) -> None:
377         self.arcs = []  # list of (label, NFAState) pairs
378
379     def addarc(self, next: "NFAState", label: Optional[Text] = None) -> None:
380         assert label is None or isinstance(label, str)
381         assert isinstance(next, NFAState)
382         self.arcs.append((label, next))
383
384
385 class DFAState(object):
386     nfaset: Dict[NFAState, Any]
387     isfinal: bool
388     arcs: Dict[Text, "DFAState"]
389
390     def __init__(self, nfaset: Dict[NFAState, Any], final: NFAState) -> None:
391         assert isinstance(nfaset, dict)
392         assert isinstance(next(iter(nfaset)), NFAState)
393         assert isinstance(final, NFAState)
394         self.nfaset = nfaset
395         self.isfinal = final in nfaset
396         self.arcs = {}  # map from label to DFAState
397
398     def addarc(self, next: "DFAState", label: Text) -> None:
399         assert isinstance(label, str)
400         assert label not in self.arcs
401         assert isinstance(next, DFAState)
402         self.arcs[label] = next
403
404     def unifystate(self, old: "DFAState", new: "DFAState") -> None:
405         for label, next in self.arcs.items():
406             if next is old:
407                 self.arcs[label] = new
408
409     def __eq__(self, other: Any) -> bool:
410         # Equality test -- ignore the nfaset instance variable
411         assert isinstance(other, DFAState)
412         if self.isfinal != other.isfinal:
413             return False
414         # Can't just return self.arcs == other.arcs, because that
415         # would invoke this method recursively, with cycles...
416         if len(self.arcs) != len(other.arcs):
417             return False
418         for label, next in self.arcs.items():
419             if next is not other.arcs.get(label):
420                 return False
421         return True
422
423     __hash__: Any = None  # For Py3 compatibility.
424
425
426 def generate_grammar(filename: Path = "Grammar.txt") -> PgenGrammar:
427     p = ParserGenerator(filename)
428     return p.make_grammar()