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Move the Grammar to the pgen module

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This commit is contained in:
Dave Halter
2018-06-26 10:08:44 +02:00
parent c1675da0cb
commit 30cf491b4f
2 changed files with 83 additions and 100 deletions
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99
parso/pgen2/grammar.py
View File

@@ -1,99 +0,0 @@
# 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.
"""This module defines the data structures used to represent a grammar.
These are a bit arcane because they are derived from the data
structures used by Python's 'pgen' parser generator.
There's also a table here mapping operators to their names in the
token module; the Python tokenize module reports all operators as the
fallback token code OP, but the parser needs the actual token code.
"""
class DFAPlan(object):
def __init__(self, next_dfa, dfa_pushes=[]):
self.next_dfa = next_dfa
self.dfa_pushes = dfa_pushes
def __repr__(self):
return '%s(%s, %s)' % (self.__class__.__name__, self.next_dfa, self.dfa_pushes)
class Grammar(object):
"""Pgen parsing tables conversion class.
Once initialized, this class supplies the grammar tables for the
parsing engine implemented by parse.py. The parsing engine
accesses the instance variables directly. The class here does not
provide initialization of the tables; several subclasses exist to
do this (see the conv and pgen modules).
"""
def __init__(self, start_nonterminal, rule_to_dfas, reserved_syntax_strings):
self.nonterminal_to_dfas = rule_to_dfas
self.reserved_syntax_strings = reserved_syntax_strings
self.start_nonterminal = start_nonterminal
self._make_grammar()
def _make_grammar(self):
# Map from grammar rule (nonterminal) name to a set of tokens.
self._first_plans = {}
nonterminals = list(self.nonterminal_to_dfas.keys())
nonterminals.sort()
for nonterminal in nonterminals:
if nonterminal not in self._first_plans:
self._calculate_first_terminals(nonterminal)
# Now that we have calculated the first terminals, we are sure that
# there is no left recursion or ambiguities.
for dfas in self.nonterminal_to_dfas.values():
for dfa_state in dfas:
for nonterminal, next_dfa in dfa_state.nonterminal_arcs.items():
for transition, pushes in self._first_plans[nonterminal].items():
dfa_state.ilabel_to_plan[transition] = DFAPlan(next_dfa, pushes)
def _calculate_first_terminals(self, nonterminal):
dfas = self.nonterminal_to_dfas[nonterminal]
new_first_plans = {}
self._first_plans[nonterminal] = None # dummy to detect left recursion
# We only need to check the first dfa. All the following ones are not
# interesting to find first terminals.
state = dfas[0]
for nonterminal2, next_ in state.nonterminal_arcs.items():
# It's a nonterminal and we have either a left recursion issue
# in the grammar or we have to recurse.
try:
first_plans2 = self._first_plans[nonterminal2]
except KeyError:
first_plans2 = self._calculate_first_terminals(nonterminal2)
else:
if first_plans2 is None:
raise ValueError("left recursion for rule %r" % nonterminal)
for t, pushes in first_plans2.items():
check = new_first_plans.get(t)
if check is not None:
raise ValueError(
"Rule %s is ambiguous; %s is the"
" start of the rule %s as well as %s."
% (nonterminal, t, nonterminal2, check[-1].from_rule)
)
new_first_plans[t] = [next_] + pushes
for transition, next_ in state.ilabel_to_plan.items():
# It's a string. We have finally found a possible first token.
new_first_plans[transition] = [next_.next_dfa]
self._first_plans[nonterminal] = new_first_plans
return new_first_plans

84
parso/pgen2/pgen.py
View File

@@ -6,6 +6,8 @@
# Modifications are dual-licensed: MIT and PSF.
"""
This module defines the data structures used to represent a grammar.
Specifying grammars in pgen is possible with this grammar::
grammar: (NEWLINE | rule)* ENDMARKER
@@ -20,10 +22,90 @@ This grammar is self-referencing.
from ast import literal_eval
from parso.pgen2.grammar import Grammar, DFAPlan
from parso.pgen2.grammar_parser import GrammarParser, NFAState
class DFAPlan(object):
def __init__(self, next_dfa, dfa_pushes=[]):
self.next_dfa = next_dfa
self.dfa_pushes = dfa_pushes
def __repr__(self):
return '%s(%s, %s)' % (self.__class__.__name__, self.next_dfa, self.dfa_pushes)
class Grammar(object):
"""Pgen parsing tables conversion class.
Once initialized, this class supplies the grammar tables for the
parsing engine implemented by parse.py. The parsing engine
accesses the instance variables directly. The class here does not
provide initialization of the tables; several subclasses exist to
do this (see the conv and pgen modules).
"""
def __init__(self, start_nonterminal, rule_to_dfas, reserved_syntax_strings):
self.nonterminal_to_dfas = rule_to_dfas # Dict[str, List[DFAState]]
self.reserved_syntax_strings = reserved_syntax_strings
self.start_nonterminal = start_nonterminal
self._make_grammar()
def _make_grammar(self):
# Map from grammar rule (nonterminal) name to a set of tokens.
self._first_plans = {}
nonterminals = list(self.nonterminal_to_dfas.keys())
nonterminals.sort()
for nonterminal in nonterminals:
if nonterminal not in self._first_plans:
self._calculate_first_terminals(nonterminal)
# Now that we have calculated the first terminals, we are sure that
# there is no left recursion or ambiguities.
for dfas in self.nonterminal_to_dfas.values():
for dfa_state in dfas:
for nonterminal, next_dfa in dfa_state.nonterminal_arcs.items():
for transition, pushes in self._first_plans[nonterminal].items():
dfa_state.ilabel_to_plan[transition] = DFAPlan(next_dfa, pushes)
def _calculate_first_terminals(self, nonterminal):
dfas = self.nonterminal_to_dfas[nonterminal]
new_first_plans = {}
self._first_plans[nonterminal] = None # dummy to detect left recursion
# We only need to check the first dfa. All the following ones are not
# interesting to find first terminals.
state = dfas[0]
for nonterminal2, next_ in state.nonterminal_arcs.items():
# It's a nonterminal and we have either a left recursion issue
# in the grammar or we have to recurse.
try:
first_plans2 = self._first_plans[nonterminal2]
except KeyError:
first_plans2 = self._calculate_first_terminals(nonterminal2)
else:
if first_plans2 is None:
raise ValueError("left recursion for rule %r" % nonterminal)
for t, pushes in first_plans2.items():
check = new_first_plans.get(t)
if check is not None:
raise ValueError(
"Rule %s is ambiguous; %s is the"
" start of the rule %s as well as %s."
% (nonterminal, t, nonterminal2, check[-1].from_rule)
)
new_first_plans[t] = [next_] + pushes
for transition, next_ in state.ilabel_to_plan.items():
# It's a string. We have finally found a possible first token.
new_first_plans[transition] = [next_.next_dfa]
self._first_plans[nonterminal] = new_first_plans
return new_first_plans
class DFAState(object):
def __init__(self, from_rule, nfa_set, final):
assert isinstance(nfa_set, set)