mirror of
https://github.com/python/cpython.git
synced 2024-12-16 05:14:41 +08:00
f2c1aa1661
Issue #26146: Add a new kind of AST node: ast.Constant. It can be used by external AST optimizers, but the compiler does not emit directly such node. An optimizer can replace the following AST nodes with ast.Constant: * ast.NameConstant: None, False, True * ast.Num: int, float, complex * ast.Str: str * ast.Bytes: bytes * ast.Tuple if items are constants too: tuple * frozenset Update code to accept ast.Constant instead of ast.Num and/or ast.Str: * compiler * docstrings * ast.literal_eval() * Tools/parser/unparse.py
377 lines
13 KiB
Python
377 lines
13 KiB
Python
#-------------------------------------------------------------------------------
|
|
# Parser for ASDL [1] definition files. Reads in an ASDL description and parses
|
|
# it into an AST that describes it.
|
|
#
|
|
# The EBNF we're parsing here: Figure 1 of the paper [1]. Extended to support
|
|
# modules and attributes after a product. Words starting with Capital letters
|
|
# are terminals. Literal tokens are in "double quotes". Others are
|
|
# non-terminals. Id is either TokenId or ConstructorId.
|
|
#
|
|
# module ::= "module" Id "{" [definitions] "}"
|
|
# definitions ::= { TypeId "=" type }
|
|
# type ::= product | sum
|
|
# product ::= fields ["attributes" fields]
|
|
# fields ::= "(" { field, "," } field ")"
|
|
# field ::= TypeId ["?" | "*"] [Id]
|
|
# sum ::= constructor { "|" constructor } ["attributes" fields]
|
|
# constructor ::= ConstructorId [fields]
|
|
#
|
|
# [1] "The Zephyr Abstract Syntax Description Language" by Wang, et. al. See
|
|
# http://asdl.sourceforge.net/
|
|
#-------------------------------------------------------------------------------
|
|
from collections import namedtuple
|
|
import re
|
|
|
|
__all__ = [
|
|
'builtin_types', 'parse', 'AST', 'Module', 'Type', 'Constructor',
|
|
'Field', 'Sum', 'Product', 'VisitorBase', 'Check', 'check']
|
|
|
|
# The following classes define nodes into which the ASDL description is parsed.
|
|
# Note: this is a "meta-AST". ASDL files (such as Python.asdl) describe the AST
|
|
# structure used by a programming language. But ASDL files themselves need to be
|
|
# parsed. This module parses ASDL files and uses a simple AST to represent them.
|
|
# See the EBNF at the top of the file to understand the logical connection
|
|
# between the various node types.
|
|
|
|
builtin_types = {'identifier', 'string', 'bytes', 'int', 'object', 'singleton',
|
|
'constant'}
|
|
|
|
class AST:
|
|
def __repr__(self):
|
|
raise NotImplementedError
|
|
|
|
class Module(AST):
|
|
def __init__(self, name, dfns):
|
|
self.name = name
|
|
self.dfns = dfns
|
|
self.types = {type.name: type.value for type in dfns}
|
|
|
|
def __repr__(self):
|
|
return 'Module({0.name}, {0.dfns})'.format(self)
|
|
|
|
class Type(AST):
|
|
def __init__(self, name, value):
|
|
self.name = name
|
|
self.value = value
|
|
|
|
def __repr__(self):
|
|
return 'Type({0.name}, {0.value})'.format(self)
|
|
|
|
class Constructor(AST):
|
|
def __init__(self, name, fields=None):
|
|
self.name = name
|
|
self.fields = fields or []
|
|
|
|
def __repr__(self):
|
|
return 'Constructor({0.name}, {0.fields})'.format(self)
|
|
|
|
class Field(AST):
|
|
def __init__(self, type, name=None, seq=False, opt=False):
|
|
self.type = type
|
|
self.name = name
|
|
self.seq = seq
|
|
self.opt = opt
|
|
|
|
def __repr__(self):
|
|
if self.seq:
|
|
extra = ", seq=True"
|
|
elif self.opt:
|
|
extra = ", opt=True"
|
|
else:
|
|
extra = ""
|
|
if self.name is None:
|
|
return 'Field({0.type}{1})'.format(self, extra)
|
|
else:
|
|
return 'Field({0.type}, {0.name}{1})'.format(self, extra)
|
|
|
|
class Sum(AST):
|
|
def __init__(self, types, attributes=None):
|
|
self.types = types
|
|
self.attributes = attributes or []
|
|
|
|
def __repr__(self):
|
|
if self.attributes:
|
|
return 'Sum({0.types}, {0.attributes})'.format(self)
|
|
else:
|
|
return 'Sum({0.types})'.format(self)
|
|
|
|
class Product(AST):
|
|
def __init__(self, fields, attributes=None):
|
|
self.fields = fields
|
|
self.attributes = attributes or []
|
|
|
|
def __repr__(self):
|
|
if self.attributes:
|
|
return 'Product({0.fields}, {0.attributes})'.format(self)
|
|
else:
|
|
return 'Product({0.fields})'.format(self)
|
|
|
|
# A generic visitor for the meta-AST that describes ASDL. This can be used by
|
|
# emitters. Note that this visitor does not provide a generic visit method, so a
|
|
# subclass needs to define visit methods from visitModule to as deep as the
|
|
# interesting node.
|
|
# We also define a Check visitor that makes sure the parsed ASDL is well-formed.
|
|
|
|
class VisitorBase(object):
|
|
"""Generic tree visitor for ASTs."""
|
|
def __init__(self):
|
|
self.cache = {}
|
|
|
|
def visit(self, obj, *args):
|
|
klass = obj.__class__
|
|
meth = self.cache.get(klass)
|
|
if meth is None:
|
|
methname = "visit" + klass.__name__
|
|
meth = getattr(self, methname, None)
|
|
self.cache[klass] = meth
|
|
if meth:
|
|
try:
|
|
meth(obj, *args)
|
|
except Exception as e:
|
|
print("Error visiting %r: %s" % (obj, e))
|
|
raise
|
|
|
|
class Check(VisitorBase):
|
|
"""A visitor that checks a parsed ASDL tree for correctness.
|
|
|
|
Errors are printed and accumulated.
|
|
"""
|
|
def __init__(self):
|
|
super(Check, self).__init__()
|
|
self.cons = {}
|
|
self.errors = 0
|
|
self.types = {}
|
|
|
|
def visitModule(self, mod):
|
|
for dfn in mod.dfns:
|
|
self.visit(dfn)
|
|
|
|
def visitType(self, type):
|
|
self.visit(type.value, str(type.name))
|
|
|
|
def visitSum(self, sum, name):
|
|
for t in sum.types:
|
|
self.visit(t, name)
|
|
|
|
def visitConstructor(self, cons, name):
|
|
key = str(cons.name)
|
|
conflict = self.cons.get(key)
|
|
if conflict is None:
|
|
self.cons[key] = name
|
|
else:
|
|
print('Redefinition of constructor {}'.format(key))
|
|
print('Defined in {} and {}'.format(conflict, name))
|
|
self.errors += 1
|
|
for f in cons.fields:
|
|
self.visit(f, key)
|
|
|
|
def visitField(self, field, name):
|
|
key = str(field.type)
|
|
l = self.types.setdefault(key, [])
|
|
l.append(name)
|
|
|
|
def visitProduct(self, prod, name):
|
|
for f in prod.fields:
|
|
self.visit(f, name)
|
|
|
|
def check(mod):
|
|
"""Check the parsed ASDL tree for correctness.
|
|
|
|
Return True if success. For failure, the errors are printed out and False
|
|
is returned.
|
|
"""
|
|
v = Check()
|
|
v.visit(mod)
|
|
|
|
for t in v.types:
|
|
if t not in mod.types and not t in builtin_types:
|
|
v.errors += 1
|
|
uses = ", ".join(v.types[t])
|
|
print('Undefined type {}, used in {}'.format(t, uses))
|
|
return not v.errors
|
|
|
|
# The ASDL parser itself comes next. The only interesting external interface
|
|
# here is the top-level parse function.
|
|
|
|
def parse(filename):
|
|
"""Parse ASDL from the given file and return a Module node describing it."""
|
|
with open(filename) as f:
|
|
parser = ASDLParser()
|
|
return parser.parse(f.read())
|
|
|
|
# Types for describing tokens in an ASDL specification.
|
|
class TokenKind:
|
|
"""TokenKind is provides a scope for enumerated token kinds."""
|
|
(ConstructorId, TypeId, Equals, Comma, Question, Pipe, Asterisk,
|
|
LParen, RParen, LBrace, RBrace) = range(11)
|
|
|
|
operator_table = {
|
|
'=': Equals, ',': Comma, '?': Question, '|': Pipe, '(': LParen,
|
|
')': RParen, '*': Asterisk, '{': LBrace, '}': RBrace}
|
|
|
|
Token = namedtuple('Token', 'kind value lineno')
|
|
|
|
class ASDLSyntaxError(Exception):
|
|
def __init__(self, msg, lineno=None):
|
|
self.msg = msg
|
|
self.lineno = lineno or '<unknown>'
|
|
|
|
def __str__(self):
|
|
return 'Syntax error on line {0.lineno}: {0.msg}'.format(self)
|
|
|
|
def tokenize_asdl(buf):
|
|
"""Tokenize the given buffer. Yield Token objects."""
|
|
for lineno, line in enumerate(buf.splitlines(), 1):
|
|
for m in re.finditer(r'\s*(\w+|--.*|.)', line.strip()):
|
|
c = m.group(1)
|
|
if c[0].isalpha():
|
|
# Some kind of identifier
|
|
if c[0].isupper():
|
|
yield Token(TokenKind.ConstructorId, c, lineno)
|
|
else:
|
|
yield Token(TokenKind.TypeId, c, lineno)
|
|
elif c[:2] == '--':
|
|
# Comment
|
|
break
|
|
else:
|
|
# Operators
|
|
try:
|
|
op_kind = TokenKind.operator_table[c]
|
|
except KeyError:
|
|
raise ASDLSyntaxError('Invalid operator %s' % c, lineno)
|
|
yield Token(op_kind, c, lineno)
|
|
|
|
class ASDLParser:
|
|
"""Parser for ASDL files.
|
|
|
|
Create, then call the parse method on a buffer containing ASDL.
|
|
This is a simple recursive descent parser that uses tokenize_asdl for the
|
|
lexing.
|
|
"""
|
|
def __init__(self):
|
|
self._tokenizer = None
|
|
self.cur_token = None
|
|
|
|
def parse(self, buf):
|
|
"""Parse the ASDL in the buffer and return an AST with a Module root.
|
|
"""
|
|
self._tokenizer = tokenize_asdl(buf)
|
|
self._advance()
|
|
return self._parse_module()
|
|
|
|
def _parse_module(self):
|
|
if self._at_keyword('module'):
|
|
self._advance()
|
|
else:
|
|
raise ASDLSyntaxError(
|
|
'Expected "module" (found {})'.format(self.cur_token.value),
|
|
self.cur_token.lineno)
|
|
name = self._match(self._id_kinds)
|
|
self._match(TokenKind.LBrace)
|
|
defs = self._parse_definitions()
|
|
self._match(TokenKind.RBrace)
|
|
return Module(name, defs)
|
|
|
|
def _parse_definitions(self):
|
|
defs = []
|
|
while self.cur_token.kind == TokenKind.TypeId:
|
|
typename = self._advance()
|
|
self._match(TokenKind.Equals)
|
|
type = self._parse_type()
|
|
defs.append(Type(typename, type))
|
|
return defs
|
|
|
|
def _parse_type(self):
|
|
if self.cur_token.kind == TokenKind.LParen:
|
|
# If we see a (, it's a product
|
|
return self._parse_product()
|
|
else:
|
|
# Otherwise it's a sum. Look for ConstructorId
|
|
sumlist = [Constructor(self._match(TokenKind.ConstructorId),
|
|
self._parse_optional_fields())]
|
|
while self.cur_token.kind == TokenKind.Pipe:
|
|
# More constructors
|
|
self._advance()
|
|
sumlist.append(Constructor(
|
|
self._match(TokenKind.ConstructorId),
|
|
self._parse_optional_fields()))
|
|
return Sum(sumlist, self._parse_optional_attributes())
|
|
|
|
def _parse_product(self):
|
|
return Product(self._parse_fields(), self._parse_optional_attributes())
|
|
|
|
def _parse_fields(self):
|
|
fields = []
|
|
self._match(TokenKind.LParen)
|
|
while self.cur_token.kind == TokenKind.TypeId:
|
|
typename = self._advance()
|
|
is_seq, is_opt = self._parse_optional_field_quantifier()
|
|
id = (self._advance() if self.cur_token.kind in self._id_kinds
|
|
else None)
|
|
fields.append(Field(typename, id, seq=is_seq, opt=is_opt))
|
|
if self.cur_token.kind == TokenKind.RParen:
|
|
break
|
|
elif self.cur_token.kind == TokenKind.Comma:
|
|
self._advance()
|
|
self._match(TokenKind.RParen)
|
|
return fields
|
|
|
|
def _parse_optional_fields(self):
|
|
if self.cur_token.kind == TokenKind.LParen:
|
|
return self._parse_fields()
|
|
else:
|
|
return None
|
|
|
|
def _parse_optional_attributes(self):
|
|
if self._at_keyword('attributes'):
|
|
self._advance()
|
|
return self._parse_fields()
|
|
else:
|
|
return None
|
|
|
|
def _parse_optional_field_quantifier(self):
|
|
is_seq, is_opt = False, False
|
|
if self.cur_token.kind == TokenKind.Asterisk:
|
|
is_seq = True
|
|
self._advance()
|
|
elif self.cur_token.kind == TokenKind.Question:
|
|
is_opt = True
|
|
self._advance()
|
|
return is_seq, is_opt
|
|
|
|
def _advance(self):
|
|
""" Return the value of the current token and read the next one into
|
|
self.cur_token.
|
|
"""
|
|
cur_val = None if self.cur_token is None else self.cur_token.value
|
|
try:
|
|
self.cur_token = next(self._tokenizer)
|
|
except StopIteration:
|
|
self.cur_token = None
|
|
return cur_val
|
|
|
|
_id_kinds = (TokenKind.ConstructorId, TokenKind.TypeId)
|
|
|
|
def _match(self, kind):
|
|
"""The 'match' primitive of RD parsers.
|
|
|
|
* Verifies that the current token is of the given kind (kind can
|
|
be a tuple, in which the kind must match one of its members).
|
|
* Returns the value of the current token
|
|
* Reads in the next token
|
|
"""
|
|
if (isinstance(kind, tuple) and self.cur_token.kind in kind or
|
|
self.cur_token.kind == kind
|
|
):
|
|
value = self.cur_token.value
|
|
self._advance()
|
|
return value
|
|
else:
|
|
raise ASDLSyntaxError(
|
|
'Unmatched {} (found {})'.format(kind, self.cur_token.kind),
|
|
self.cur_token.lineno)
|
|
|
|
def _at_keyword(self, keyword):
|
|
return (self.cur_token.kind == TokenKind.TypeId and
|
|
self.cur_token.value == keyword)
|