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Add support for PEP 695 syntax (#3703)
[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     filename: Path
34     stream: IO[Text]
35     generator: Iterator[GoodTokenInfo]
36     first: Dict[Text, Optional[Dict[Text, int]]]
37
38     def __init__(self, filename: Path, stream: Optional[IO[Text]] = None) -> None:
39         close_stream = None
40         if stream is None:
41             stream = open(filename, encoding="utf-8")
42             close_stream = stream.close
43         self.filename = filename
44         self.stream = stream
45         self.generator = tokenize.generate_tokens(stream.readline)
46         self.gettoken()  # Initialize lookahead
47         self.dfas, self.startsymbol = self.parse()
48         if close_stream is not None:
49             close_stream()
50         self.first = {}  # map from symbol name to set of tokens
51         self.addfirstsets()
52
53     def make_grammar(self) -> PgenGrammar:
54         c = PgenGrammar()
55         names = list(self.dfas.keys())
56         names.sort()
57         names.remove(self.startsymbol)
58         names.insert(0, self.startsymbol)
59         for name in names:
60             i = 256 + len(c.symbol2number)
61             c.symbol2number[name] = i
62             c.number2symbol[i] = name
63         for name in names:
64             dfa = self.dfas[name]
65             states = []
66             for state in dfa:
67                 arcs = []
68                 for label, next in sorted(state.arcs.items()):
69                     arcs.append((self.make_label(c, label), dfa.index(next)))
70                 if state.isfinal:
71                     arcs.append((0, dfa.index(state)))
72                 states.append(arcs)
73             c.states.append(states)
74             c.dfas[c.symbol2number[name]] = (states, self.make_first(c, name))
75         c.start = c.symbol2number[self.startsymbol]
76         return c
77
78     def make_first(self, c: PgenGrammar, name: Text) -> Dict[int, int]:
79         rawfirst = self.first[name]
80         assert rawfirst is not None
81         first = {}
82         for label in sorted(rawfirst):
83             ilabel = self.make_label(c, label)
84             ##assert ilabel not in first # XXX failed on <> ... !=
85             first[ilabel] = 1
86         return first
87
88     def make_label(self, c: PgenGrammar, label: Text) -> int:
89         # XXX Maybe this should be a method on a subclass of converter?
90         ilabel = len(c.labels)
91         if label[0].isalpha():
92             # Either a symbol name or a named token
93             if label in c.symbol2number:
94                 # A symbol name (a non-terminal)
95                 if label in c.symbol2label:
96                     return c.symbol2label[label]
97                 else:
98                     c.labels.append((c.symbol2number[label], None))
99                     c.symbol2label[label] = ilabel
100                     return ilabel
101             else:
102                 # A named token (NAME, NUMBER, STRING)
103                 itoken = getattr(token, label, None)
104                 assert isinstance(itoken, int), label
105                 assert itoken in token.tok_name, label
106                 if itoken in c.tokens:
107                     return c.tokens[itoken]
108                 else:
109                     c.labels.append((itoken, None))
110                     c.tokens[itoken] = ilabel
111                     return ilabel
112         else:
113             # Either a keyword or an operator
114             assert label[0] in ('"', "'"), label
115             value = eval(label)
116             if value[0].isalpha():
117                 if label[0] == '"':
118                     keywords = c.soft_keywords
119                 else:
120                     keywords = c.keywords
121
122                 # A keyword
123                 if value in keywords:
124                     return keywords[value]
125                 else:
126                     c.labels.append((token.NAME, value))
127                     keywords[value] = ilabel
128                     return ilabel
129             else:
130                 # An operator (any non-numeric token)
131                 itoken = grammar.opmap[value]  # Fails if unknown token
132                 if itoken in c.tokens:
133                     return c.tokens[itoken]
134                 else:
135                     c.labels.append((itoken, None))
136                     c.tokens[itoken] = ilabel
137                     return ilabel
138
139     def addfirstsets(self) -> None:
140         names = list(self.dfas.keys())
141         names.sort()
142         for name in names:
143             if name not in self.first:
144                 self.calcfirst(name)
145             # print name, self.first[name].keys()
146
147     def calcfirst(self, name: Text) -> None:
148         dfa = self.dfas[name]
149         self.first[name] = None  # dummy to detect left recursion
150         state = dfa[0]
151         totalset: Dict[str, int] = {}
152         overlapcheck = {}
153         for label, next in state.arcs.items():
154             if label in self.dfas:
155                 if label in self.first:
156                     fset = self.first[label]
157                     if fset is None:
158                         raise ValueError("recursion for rule %r" % name)
159                 else:
160                     self.calcfirst(label)
161                     fset = self.first[label]
162                     assert fset is not None
163                 totalset.update(fset)
164                 overlapcheck[label] = fset
165             else:
166                 totalset[label] = 1
167                 overlapcheck[label] = {label: 1}
168         inverse: Dict[str, str] = {}
169         for label, itsfirst in overlapcheck.items():
170             for symbol in itsfirst:
171                 if symbol in inverse:
172                     raise ValueError(
173                         "rule %s is ambiguous; %s is in the first sets of %s as well"
174                         " as %s" % (name, symbol, label, inverse[symbol])
175                     )
176                 inverse[symbol] = label
177         self.first[name] = totalset
178
179     def parse(self) -> Tuple[Dict[Text, List["DFAState"]], Text]:
180         dfas = {}
181         startsymbol: Optional[str] = None
182         # MSTART: (NEWLINE | RULE)* ENDMARKER
183         while self.type != token.ENDMARKER:
184             while self.type == token.NEWLINE:
185                 self.gettoken()
186             # RULE: NAME ':' RHS NEWLINE
187             name = self.expect(token.NAME)
188             self.expect(token.OP, ":")
189             a, z = self.parse_rhs()
190             self.expect(token.NEWLINE)
191             # self.dump_nfa(name, a, z)
192             dfa = self.make_dfa(a, z)
193             # self.dump_dfa(name, dfa)
194             oldlen = len(dfa)
195             self.simplify_dfa(dfa)
196             newlen = len(dfa)
197             dfas[name] = dfa
198             # print name, oldlen, newlen
199             if startsymbol is None:
200                 startsymbol = name
201         assert startsymbol is not None
202         return dfas, startsymbol
203
204     def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
205         # To turn an NFA into a DFA, we define the states of the DFA
206         # to correspond to *sets* of states of the NFA.  Then do some
207         # state reduction.  Let's represent sets as dicts with 1 for
208         # values.
209         assert isinstance(start, NFAState)
210         assert isinstance(finish, NFAState)
211
212         def closure(state: NFAState) -> Dict[NFAState, int]:
213             base: Dict[NFAState, int] = {}
214             addclosure(state, base)
215             return base
216
217         def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
218             assert isinstance(state, NFAState)
219             if state in base:
220                 return
221             base[state] = 1
222             for label, next in state.arcs:
223                 if label is None:
224                     addclosure(next, base)
225
226         states = [DFAState(closure(start), finish)]
227         for state in states:  # NB states grows while we're iterating
228             arcs: Dict[str, Dict[NFAState, int]] = {}
229             for nfastate in state.nfaset:
230                 for label, next in nfastate.arcs:
231                     if label is not None:
232                         addclosure(next, arcs.setdefault(label, {}))
233             for label, nfaset in sorted(arcs.items()):
234                 for st in states:
235                     if st.nfaset == nfaset:
236                         break
237                 else:
238                     st = DFAState(nfaset, finish)
239                     states.append(st)
240                 state.addarc(st, label)
241         return states  # List of DFAState instances; first one is start
242
243     def dump_nfa(self, name: Text, start: "NFAState", finish: "NFAState") -> None:
244         print("Dump of NFA for", name)
245         todo = [start]
246         for i, state in enumerate(todo):
247             print("  State", i, state is finish and "(final)" or "")
248             for label, next in state.arcs:
249                 if next in todo:
250                     j = todo.index(next)
251                 else:
252                     j = len(todo)
253                     todo.append(next)
254                 if label is None:
255                     print("    -> %d" % j)
256                 else:
257                     print("    %s -> %d" % (label, j))
258
259     def dump_dfa(self, name: Text, dfa: Sequence["DFAState"]) -> None:
260         print("Dump of DFA for", name)
261         for i, state in enumerate(dfa):
262             print("  State", i, state.isfinal and "(final)" or "")
263             for label, next in sorted(state.arcs.items()):
264                 print("    %s -> %d" % (label, dfa.index(next)))
265
266     def simplify_dfa(self, dfa: List["DFAState"]) -> None:
267         # This is not theoretically optimal, but works well enough.
268         # Algorithm: repeatedly look for two states that have the same
269         # set of arcs (same labels pointing to the same nodes) and
270         # unify them, until things stop changing.
271
272         # dfa is a list of DFAState instances
273         changes = True
274         while changes:
275             changes = False
276             for i, state_i in enumerate(dfa):
277                 for j in range(i + 1, len(dfa)):
278                     state_j = dfa[j]
279                     if state_i == state_j:
280                         # print "  unify", i, j
281                         del dfa[j]
282                         for state in dfa:
283                             state.unifystate(state_j, state_i)
284                         changes = True
285                         break
286
287     def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
288         # RHS: ALT ('|' ALT)*
289         a, z = self.parse_alt()
290         if self.value != "|":
291             return a, z
292         else:
293             aa = NFAState()
294             zz = NFAState()
295             aa.addarc(a)
296             z.addarc(zz)
297             while self.value == "|":
298                 self.gettoken()
299                 a, z = self.parse_alt()
300                 aa.addarc(a)
301                 z.addarc(zz)
302             return aa, zz
303
304     def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
305         # ALT: ITEM+
306         a, b = self.parse_item()
307         while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
308             c, d = self.parse_item()
309             b.addarc(c)
310             b = d
311         return a, b
312
313     def parse_item(self) -> Tuple["NFAState", "NFAState"]:
314         # ITEM: '[' RHS ']' | ATOM ['+' | '*']
315         if self.value == "[":
316             self.gettoken()
317             a, z = self.parse_rhs()
318             self.expect(token.OP, "]")
319             a.addarc(z)
320             return a, z
321         else:
322             a, z = self.parse_atom()
323             value = self.value
324             if value not in ("+", "*"):
325                 return a, z
326             self.gettoken()
327             z.addarc(a)
328             if value == "+":
329                 return a, z
330             else:
331                 return a, a
332
333     def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
334         # ATOM: '(' RHS ')' | NAME | STRING
335         if self.value == "(":
336             self.gettoken()
337             a, z = self.parse_rhs()
338             self.expect(token.OP, ")")
339             return a, z
340         elif self.type in (token.NAME, token.STRING):
341             a = NFAState()
342             z = NFAState()
343             a.addarc(z, self.value)
344             self.gettoken()
345             return a, z
346         else:
347             self.raise_error(
348                 "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
349             )
350             assert False
351
352     def expect(self, type: int, value: Optional[Any] = None) -> Text:
353         if self.type != type or (value is not None and self.value != value):
354             self.raise_error(
355                 "expected %s/%s, got %s/%s", type, value, self.type, self.value
356             )
357         value = self.value
358         self.gettoken()
359         return value
360
361     def gettoken(self) -> None:
362         tup = next(self.generator)
363         while tup[0] in (tokenize.COMMENT, tokenize.NL):
364             tup = next(self.generator)
365         self.type, self.value, self.begin, self.end, self.line = tup
366         # print token.tok_name[self.type], repr(self.value)
367
368     def raise_error(self, msg: str, *args: Any) -> NoReturn:
369         if args:
370             try:
371                 msg = msg % args
372             except:
373                 msg = " ".join([msg] + list(map(str, args)))
374         raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
375
376
377 class NFAState(object):
378     arcs: List[Tuple[Optional[Text], "NFAState"]]
379
380     def __init__(self) -> None:
381         self.arcs = []  # list of (label, NFAState) pairs
382
383     def addarc(self, next: "NFAState", label: Optional[Text] = None) -> None:
384         assert label is None or isinstance(label, str)
385         assert isinstance(next, NFAState)
386         self.arcs.append((label, next))
387
388
389 class DFAState(object):
390     nfaset: Dict[NFAState, Any]
391     isfinal: bool
392     arcs: Dict[Text, "DFAState"]
393
394     def __init__(self, nfaset: Dict[NFAState, Any], final: NFAState) -> None:
395         assert isinstance(nfaset, dict)
396         assert isinstance(next(iter(nfaset)), NFAState)
397         assert isinstance(final, NFAState)
398         self.nfaset = nfaset
399         self.isfinal = final in nfaset
400         self.arcs = {}  # map from label to DFAState
401
402     def addarc(self, next: "DFAState", label: Text) -> None:
403         assert isinstance(label, str)
404         assert label not in self.arcs
405         assert isinstance(next, DFAState)
406         self.arcs[label] = next
407
408     def unifystate(self, old: "DFAState", new: "DFAState") -> None:
409         for label, next in self.arcs.items():
410             if next is old:
411                 self.arcs[label] = new
412
413     def __eq__(self, other: Any) -> bool:
414         # Equality test -- ignore the nfaset instance variable
415         assert isinstance(other, DFAState)
416         if self.isfinal != other.isfinal:
417             return False
418         # Can't just return self.arcs == other.arcs, because that
419         # would invoke this method recursively, with cycles...
420         if len(self.arcs) != len(other.arcs):
421             return False
422         for label, next in self.arcs.items():
423             if next is not other.arcs.get(label):
424                 return False
425         return True
426
427     __hash__: Any = None  # For Py3 compatibility.
428
429
430 def generate_grammar(filename: Path = "Grammar.txt") -> PgenGrammar:
431     p = ParserGenerator(filename)
432     return p.make_grammar()