mirror of
https://github.com/davidhalter/parso.git
synced 2026-01-10 21:42:44 +08:00
300 lines
10 KiB
Python
300 lines
10 KiB
Python
# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
|
|
# Licensed to PSF under a Contributor Agreement.
|
|
|
|
# Modifications:
|
|
# Copyright David Halter and Contributors
|
|
# Modifications are dual-licensed: MIT and PSF.
|
|
|
|
"""
|
|
Specifying grammars in pgen is possible with this grammar::
|
|
|
|
grammar: (NEWLINE | rule)* ENDMARKER
|
|
rule: NAME ':' rhs NEWLINE
|
|
rhs: items ('|' items)*
|
|
items: item+
|
|
item: '[' rhs ']' | atom ['+' | '*']
|
|
atom: '(' rhs ')' | NAME | STRING
|
|
|
|
This grammar is self-referencing.
|
|
"""
|
|
|
|
from parso.pgen2.grammar import Grammar
|
|
from parso.python import token
|
|
from parso.pgen2.grammar_parser import GrammarParser, NFAState
|
|
|
|
|
|
class ParserGenerator(object):
|
|
def __init__(self, rule_to_dfas, token_namespace):
|
|
self._token_namespace = token_namespace
|
|
self.dfas = rule_to_dfas
|
|
|
|
def make_grammar(self, grammar):
|
|
self._first = {} # map from symbol name to set of tokens
|
|
self._addfirstsets()
|
|
|
|
names = list(self.dfas.keys())
|
|
names.sort()
|
|
for name in names:
|
|
i = 256 + len(grammar.symbol2number)
|
|
grammar.symbol2number[name] = i
|
|
grammar.number2symbol[i] = name
|
|
for name in names:
|
|
dfa = self.dfas[name]
|
|
states = []
|
|
for state in dfa:
|
|
arcs = []
|
|
for label, next in state.arcs.items():
|
|
arcs.append((self._make_label(grammar, label), dfa.index(next)))
|
|
if state.isfinal:
|
|
arcs.append((0, dfa.index(state)))
|
|
states.append(arcs)
|
|
grammar.states.append(states)
|
|
grammar.dfas[grammar.symbol2number[name]] = (states, self._make_first(grammar, name))
|
|
return grammar
|
|
|
|
def _make_first(self, grammar, name):
|
|
rawfirst = self._first[name]
|
|
first = {}
|
|
for label in rawfirst:
|
|
ilabel = self._make_label(grammar, label)
|
|
##assert ilabel not in first # XXX failed on <> ... !=
|
|
first[ilabel] = 1
|
|
return first
|
|
|
|
def _make_label(self, grammar, label):
|
|
# XXX Maybe this should be a method on a subclass of converter?
|
|
ilabel = len(grammar.labels)
|
|
if label[0].isalpha():
|
|
# Either a symbol name or a named token
|
|
if label in grammar.symbol2number:
|
|
# A symbol name (a non-terminal)
|
|
if label in grammar.symbol2label:
|
|
return grammar.symbol2label[label]
|
|
else:
|
|
grammar.labels.append((grammar.symbol2number[label], None))
|
|
grammar.symbol2label[label] = ilabel
|
|
grammar.label2symbol[ilabel] = label
|
|
return ilabel
|
|
else:
|
|
# A named token (NAME, NUMBER, STRING)
|
|
itoken = getattr(self._token_namespace, label, None)
|
|
assert isinstance(itoken, int), label
|
|
if itoken in grammar.tokens:
|
|
return grammar.tokens[itoken]
|
|
else:
|
|
grammar.labels.append((itoken, None))
|
|
grammar.tokens[itoken] = ilabel
|
|
return ilabel
|
|
else:
|
|
# Either a keyword or an operator
|
|
assert label[0] in ('"', "'"), label
|
|
value = eval(label)
|
|
if value[0].isalpha():
|
|
# A keyword
|
|
if value in grammar.keywords:
|
|
return grammar.keywords[value]
|
|
else:
|
|
# TODO this might be an issue?! Using token.NAME here?
|
|
grammar.labels.append((token.NAME, value))
|
|
grammar.keywords[value] = ilabel
|
|
return ilabel
|
|
else:
|
|
# An operator (any non-numeric token)
|
|
itoken = self._token_namespace.generate_token_id(value)
|
|
if itoken in grammar.tokens:
|
|
return grammar.tokens[itoken]
|
|
else:
|
|
grammar.labels.append((itoken, None))
|
|
grammar.tokens[itoken] = ilabel
|
|
return ilabel
|
|
|
|
def _addfirstsets(self):
|
|
names = list(self.dfas.keys())
|
|
names.sort()
|
|
for name in names:
|
|
if name not in self._first:
|
|
self._calcfirst(name)
|
|
#print name, self._first[name].keys()
|
|
|
|
def _calcfirst(self, name):
|
|
dfa = self.dfas[name]
|
|
self._first[name] = None # dummy to detect left recursion
|
|
state = dfa[0]
|
|
totalset = {}
|
|
overlapcheck = {}
|
|
for label, next in state.arcs.items():
|
|
if label in self.dfas:
|
|
if label in self._first:
|
|
fset = self._first[label]
|
|
if fset is None:
|
|
raise ValueError("recursion for rule %r" % name)
|
|
else:
|
|
self._calcfirst(label)
|
|
fset = self._first[label]
|
|
totalset.update(fset)
|
|
overlapcheck[label] = fset
|
|
else:
|
|
totalset[label] = 1
|
|
overlapcheck[label] = {label: 1}
|
|
inverse = {}
|
|
for label, itsfirst in overlapcheck.items():
|
|
for symbol in itsfirst:
|
|
if symbol in inverse:
|
|
raise ValueError("rule %s is ambiguous; %s is in the"
|
|
" first sets of %s as well as %s" %
|
|
(name, symbol, label, inverse[symbol]))
|
|
inverse[symbol] = label
|
|
self._first[name] = totalset
|
|
|
|
|
|
class DFAState(object):
|
|
def __init__(self, nfaset, final):
|
|
assert isinstance(nfaset, dict)
|
|
assert isinstance(next(iter(nfaset)), NFAState)
|
|
assert isinstance(final, NFAState)
|
|
self.nfaset = nfaset
|
|
self.isfinal = final in nfaset
|
|
self.arcs = {} # map from label to DFAState
|
|
|
|
def add_arc(self, next, label):
|
|
assert isinstance(label, str)
|
|
assert label not in self.arcs
|
|
assert isinstance(next, DFAState)
|
|
self.arcs[label] = next
|
|
|
|
def unifystate(self, old, new):
|
|
for label, next in self.arcs.items():
|
|
if next is old:
|
|
self.arcs[label] = new
|
|
|
|
def __eq__(self, other):
|
|
# Equality test -- ignore the nfaset instance variable
|
|
assert isinstance(other, DFAState)
|
|
if self.isfinal != other.isfinal:
|
|
return False
|
|
# Can't just return self.arcs == other.arcs, because that
|
|
# would invoke this method recursively, with cycles...
|
|
if len(self.arcs) != len(other.arcs):
|
|
return False
|
|
for label, next in self.arcs.items():
|
|
if next is not other.arcs.get(label):
|
|
return False
|
|
return True
|
|
|
|
__hash__ = None # For Py3 compatibility.
|
|
|
|
|
|
def _simplify_dfas(dfas):
|
|
# This is not theoretically optimal, but works well enough.
|
|
# Algorithm: repeatedly look for two states that have the same
|
|
# set of arcs (same labels pointing to the same nodes) and
|
|
# unify them, until things stop changing.
|
|
|
|
# dfas is a list of DFAState instances
|
|
changes = True
|
|
while changes:
|
|
changes = False
|
|
for i, state_i in enumerate(dfas):
|
|
for j in range(i + 1, len(dfas)):
|
|
state_j = dfas[j]
|
|
if state_i == state_j:
|
|
#print " unify", i, j
|
|
del dfas[j]
|
|
for state in dfas:
|
|
state.unifystate(state_j, state_i)
|
|
changes = True
|
|
break
|
|
|
|
|
|
def _make_dfas(start, finish):
|
|
# To turn an NFA into a DFA, we define the states of the DFA
|
|
# to correspond to *sets* of states of the NFA. Then do some
|
|
# state reduction. Let's represent sets as dicts with 1 for
|
|
# values.
|
|
assert isinstance(start, NFAState)
|
|
assert isinstance(finish, NFAState)
|
|
|
|
def closure(state):
|
|
base = {}
|
|
addclosure(state, base)
|
|
return base
|
|
|
|
def addclosure(state, base):
|
|
assert isinstance(state, NFAState)
|
|
if state in base:
|
|
return
|
|
base[state] = 1
|
|
for label, next in state.arcs:
|
|
if label is None:
|
|
addclosure(next, base)
|
|
|
|
states = [DFAState(closure(start), finish)]
|
|
for state in states: # NB states grows while we're iterating
|
|
arcs = {}
|
|
for nfastate in state.nfaset:
|
|
for label, next in nfastate.arcs:
|
|
if label is not None:
|
|
addclosure(next, arcs.setdefault(label, {}))
|
|
for label, nfaset in arcs.items():
|
|
for st in states:
|
|
if st.nfaset == nfaset:
|
|
break
|
|
else:
|
|
st = DFAState(nfaset, finish)
|
|
states.append(st)
|
|
state.add_arc(st, label)
|
|
return states # List of DFAState instances; first one is start
|
|
|
|
|
|
def _dump_nfa(start, finish):
|
|
print("Dump of NFA for", start.from_rule)
|
|
todo = [start]
|
|
for i, state in enumerate(todo):
|
|
print(" State", i, state is finish and "(final)" or "")
|
|
for label, next in state.arcs:
|
|
if next in todo:
|
|
j = todo.index(next)
|
|
else:
|
|
j = len(todo)
|
|
todo.append(next)
|
|
if label is None:
|
|
print(" -> %d" % j)
|
|
else:
|
|
print(" %s -> %d" % (label, j))
|
|
|
|
|
|
def _dump_dfas(name, dfas):
|
|
print("Dump of DFA for", name)
|
|
for i, state in enumerate(dfas):
|
|
print(" State", i, state.isfinal and "(final)" or "")
|
|
for label, next in state.arcs.items():
|
|
print(" %s -> %d" % (label, dfas.index(next)))
|
|
|
|
|
|
def generate_grammar(bnf_grammar, token_namespace):
|
|
"""
|
|
``bnf_text`` is a grammar in extended BNF (using * for repetition, + for
|
|
at-least-once repetition, [] for optional parts, | for alternatives and ()
|
|
for grouping).
|
|
|
|
It's not EBNF according to ISO/IEC 14977. It's a dialect Python uses in its
|
|
own parser.
|
|
"""
|
|
rule_to_dfas = {}
|
|
start_symbol = None
|
|
for nfa_a, nfa_z in GrammarParser(bnf_grammar).parse():
|
|
#_dump_nfa(a, z)
|
|
dfas = _make_dfas(nfa_a, nfa_z)
|
|
#_dump_dfas(self._current_rule_name, dfas)
|
|
# oldlen = len(dfas)
|
|
_simplify_dfas(dfas)
|
|
# newlen = len(dfas)
|
|
rule_to_dfas[nfa_a.from_rule] = dfas
|
|
#print(self._current_rule_name, oldlen, newlen)
|
|
|
|
if start_symbol is None:
|
|
start_symbol = nfa_a.from_rule
|
|
|
|
p = ParserGenerator(rule_to_dfas, token_namespace)
|
|
return p.make_grammar(Grammar(bnf_grammar, start_symbol))
|