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#-----------------------------------------------------------------
# plyparser.py
#
# PLYParser class and other utilities for simplifying programming
# parsers with PLY
#
# Eli Bendersky [https://eli.thegreenplace.net/]
# License: BSD
#-----------------------------------------------------------------
import warnings
class Coord(object):
""" Coordinates of a syntactic element. Consists of:
- File name
- Line number
- (optional) column number, for the Lexer
"""
__slots__ = ('file', 'line', 'column', '__weakref__')
def __init__(self, file, line, column=None):
self.file = file
self.line = line
self.column = column
def __str__(self):
str = "%s:%s" % (self.file, self.line)
if self.column: str += ":%s" % self.column
return str
class ParseError(Exception): pass
class PLYParser(object):
def _create_opt_rule(self, rulename):
""" Given a rule name, creates an optional ply.yacc rule
for it. The name of the optional rule is
<rulename>_opt
"""
optname = rulename + '_opt'
def optrule(self, p):
p[0] = p[1]
optrule.__doc__ = '%s : empty\n| %s' % (optname, rulename)
optrule.__name__ = 'p_%s' % optname
setattr(self.__class__, optrule.__name__, optrule)
def _coord(self, lineno, column=None):
return Coord(
file=self.clex.filename,
line=lineno,
column=column)
def _token_coord(self, p, token_idx):
""" Returns the coordinates for the YaccProduction object 'p' indexed
with 'token_idx'. The coordinate includes the 'lineno' and
'column'. Both follow the lex semantic, starting from 1.
"""
last_cr = p.lexer.lexer.lexdata.rfind('\n', 0, p.lexpos(token_idx))
if last_cr < 0:
last_cr = -1
column = (p.lexpos(token_idx) - (last_cr))
return self._coord(p.lineno(token_idx), column)
def _parse_error(self, msg, coord):
raise ParseError("%s: %s" % (coord, msg))
def parameterized(*params):
""" Decorator to create parameterized rules.
Parameterized rule methods must be named starting with 'p_' and contain
'xxx', and their docstrings may contain 'xxx' and 'yyy'. These will be
replaced by the given parameter tuples. For example, ``p_xxx_rule()`` with
docstring 'xxx_rule : yyy' when decorated with
``@parameterized(('id', 'ID'))`` produces ``p_id_rule()`` with the docstring
'id_rule : ID'. Using multiple tuples produces multiple rules.
"""
def decorate(rule_func):
rule_func._params = params
return rule_func
return decorate
def template(cls):
""" Class decorator to generate rules from parameterized rule templates.
See `parameterized` for more information on parameterized rules.
"""
issued_nodoc_warning = False
for attr_name in dir(cls):
if attr_name.startswith('p_'):
method = getattr(cls, attr_name)
if hasattr(method, '_params'):
# Remove the template method
delattr(cls, attr_name)
# Create parameterized rules from this method; only run this if
# the method has a docstring. This is to address an issue when
# pycparser's users are installed in -OO mode which strips
# docstrings away.
# See: https://github.com/eliben/pycparser/pull/198/ and
# https://github.com/eliben/pycparser/issues/197
# for discussion.
if method.__doc__ is not None:
_create_param_rules(cls, method)
elif not issued_nodoc_warning:
warnings.warn(
'parsing methods must have __doc__ for pycparser to work properly',
RuntimeWarning,
stacklevel=2)
issued_nodoc_warning = True
return cls
def _create_param_rules(cls, func):
""" Create ply.yacc rules based on a parameterized rule function
Generates new methods (one per each pair of parameters) based on the
template rule function `func`, and attaches them to `cls`. The rule
function's parameters must be accessible via its `_params` attribute.
"""
for xxx, yyy in func._params:
# Use the template method's body for each new method
def param_rule(self, p):
func(self, p)
# Substitute in the params for the grammar rule and function name
param_rule.__doc__ = func.__doc__.replace('xxx', xxx).replace('yyy', yyy)
param_rule.__name__ = func.__name__.replace('xxx', xxx)
# Attach the new method to the class
setattr(cls, param_rule.__name__, param_rule)
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