386 lines
13 KiB
Python
386 lines
13 KiB
Python
# -----------------------------------------------------------------
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# _ast_gen.py
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#
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# Generates the AST Node classes from a specification given in
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# a configuration file. Run 'make regen-ast' from the repository root
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# to regenerate c_ast.py from _c_ast.cfg and format the code.
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# This module can also be run as a script (from the repo root or the
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# pycparser/ directory); then run 'make format' from the repo root.
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#
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# The design of this module was inspired by astgen.py from the
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# Python 2.5 code-base.
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#
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# Eli Bendersky [https://eli.thegreenplace.net/]
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# License: BSD
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# -----------------------------------------------------------------
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import os
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from string import Template
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from typing import IO
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class ASTCodeGenerator:
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def __init__(self, cfg_filename="_c_ast.cfg"):
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"""Initialize the code generator from a configuration
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file.
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"""
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self.cfg_filename = cfg_filename
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self.node_cfg = [
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NodeCfg(name, contents)
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for (name, contents) in self.parse_cfgfile(cfg_filename)
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]
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def generate(self, file: IO[str]) -> None:
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"""Generates the code into file, an open file buffer."""
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src = Template(_PROLOGUE_COMMENT).substitute(cfg_filename=self.cfg_filename)
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src += _PROLOGUE_CODE
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for node_cfg in self.node_cfg:
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src += node_cfg.generate_source() + "\n\n"
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file.write(src)
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def parse_cfgfile(self, filename):
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"""Parse the configuration file and yield pairs of
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(name, contents) for each node.
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"""
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with open(filename, "r") as f:
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for line in f:
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line = line.strip()
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if not line or line.startswith("#"):
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continue
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colon_i = line.find(":")
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lbracket_i = line.find("[")
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# A field's default may contain []; find the outer closing bracket.
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rbracket_i = line.rfind("]")
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if colon_i < 1 or lbracket_i <= colon_i or rbracket_i <= lbracket_i:
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raise RuntimeError(f"Invalid line in {filename}:\n{line}\n")
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name = line[:colon_i]
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val = line[lbracket_i + 1 : rbracket_i]
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vallist = [v.strip() for v in val.split(",")] if val else []
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yield name, vallist
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class NodeCfg:
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"""Node configuration.
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name: node name
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contents: a list of contents - attributes and child nodes
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See comment at the top of the configuration file for details.
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"""
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def __init__(self, name, contents):
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self.name = name
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self.all_entries = []
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self.attr = []
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self.child = []
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self.seq_child = []
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self.defaults = {}
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for entry in contents:
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entry, has_default, default = entry.partition("=")
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entry = entry.strip()
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clean_entry = entry.rstrip("*")
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self.all_entries.append(clean_entry)
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if has_default:
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default = default.strip()
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if default not in ("None", "[]"):
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raise RuntimeError(
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f"Unsupported default {default!r} for {name}.{clean_entry}; "
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"expected None or []"
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)
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self.defaults[clean_entry] = default
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if entry.endswith("**"):
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self.seq_child.append(clean_entry)
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elif entry.endswith("*"):
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self.child.append(clean_entry)
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else:
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self.attr.append(entry)
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def generate_source(self):
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src = self._gen_init()
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src += "\n" + self._gen_children()
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src += "\n" + self._gen_iter()
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src += "\n" + self._gen_attr_names()
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return src
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def _gen_init(self):
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src = f"class {self.name}(Node):\n"
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args = ["self"]
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args.extend(name for name in self.all_entries if name not in self.defaults)
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args.append("coord=None")
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# Defaulted fields are keyword-only so adding one doesn't shift coord
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# in existing positional calls. Both supported defaults use None here;
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# list defaults are initialized separately for each instance below.
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if self.defaults:
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args.append("*")
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args.extend(f"{name}=None" for name in self.defaults)
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arglist = f"({', '.join(args)})"
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# Keep coord and __weakref__ last: Node.__repr__ relies on their
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# positions when iterating over the node's fields.
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slots = ", ".join(
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repr(name) for name in self.all_entries + ["coord", "__weakref__"]
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)
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src += f" __slots__ = ({slots})\n"
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src += f" def __init__{arglist}:\n"
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for name in self.all_entries + ["coord"]:
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if self.defaults.get(name) == "[]":
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src += f" self.{name} = [] if {name} is None else {name}\n"
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else:
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src += f" self.{name} = {name}\n"
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return src
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def _gen_children(self):
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src = " def children(self):\n"
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if self.all_entries:
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src += " nodelist = []\n"
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for child in self.child:
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src += f" if self.{child} is not None:\n"
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src += f' nodelist.append(("{child}", self.{child}))\n'
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for seq_child in self.seq_child:
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src += f" for i, child in enumerate(self.{seq_child} or []):\n"
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src += f' nodelist.append((f"{seq_child}[{{i}}]", child))\n'
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src += " return tuple(nodelist)\n"
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else:
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src += " return ()\n"
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return src
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def _gen_iter(self):
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src = " def __iter__(self):\n"
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if self.all_entries:
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for child in self.child:
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src += f" if self.{child} is not None:\n"
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src += f" yield self.{child}\n"
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for seq_child in self.seq_child:
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src += f" yield from self.{seq_child} or []\n"
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if not (self.child or self.seq_child):
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# Empty generator
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src += " return\n" + " yield\n"
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else:
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# Empty generator
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src += " return\n" + " yield\n"
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return src
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def _gen_attr_names(self):
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src = " attr_names = (" + "".join(f"{nm!r}, " for nm in self.attr) + ")"
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return src
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_PROLOGUE_COMMENT = r"""#-----------------------------------------------------------------
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# ** ATTENTION **
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# This code was automatically generated from _c_ast.cfg
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#
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# Do not modify it directly. Modify the configuration file and
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# run 'make regen-ast' from the repository root to regenerate and format it.
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# ** ** *** ** **
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#
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# The order of generated __slots__ is significant to Node.__repr__.
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# ruff: noqa: RUF023
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#
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# pycparser: c_ast.py
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#
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# AST Node classes.
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#
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# Eli Bendersky [https://eli.thegreenplace.net/]
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# License: BSD
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#-----------------------------------------------------------------
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"""
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_PROLOGUE_CODE = r'''
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import sys
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from typing import IO, Any, ClassVar
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def _repr(obj):
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"""
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Get the representation of an object, with dedicated pprint-like format for lists.
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"""
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if isinstance(obj, list):
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return '[' + (',\n '.join(_repr(e).replace('\n', '\n ') for e in obj)) + '\n]'
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else:
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return repr(obj)
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class Node:
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__slots__ = ()
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""" Abstract base class for AST nodes.
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"""
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attr_names: ClassVar[tuple[str, ...]] = ()
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coord: Any | None
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def __repr__(self):
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""" Generates a python representation of the current node
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"""
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result = self.__class__.__name__ + '('
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indent = ''
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separator = ''
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for name in self.__slots__[:-2]:
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result += separator
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result += indent
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result += name + '=' + (_repr(getattr(self, name)).replace('\n', '\n ' + (' ' * (len(name) + len(self.__class__.__name__)))))
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separator = ','
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indent = '\n ' + (' ' * len(self.__class__.__name__))
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result += indent + ')'
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return result
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def children(self):
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"""Return a tuple of (name, child) pairs for immediate child nodes.
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Names identify the field and, for list fields, the index, such as
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"type" or "ext[0]". Optional children that are None are omitted.
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The returned tuple supports len() and indexing. Iterating over the
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node itself yields just the child nodes, without their names.
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"""
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def show(
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self,
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buf: IO[str] = sys.stdout,
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offset: int = 0,
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attrnames: bool = False,
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showemptyattrs: bool = True,
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nodenames: bool = False,
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showcoord: bool = False,
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_my_node_name: str | None = None,
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):
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""" Pretty print the Node and all its attributes and
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children (recursively) to a buffer.
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buf:
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Open IO buffer into which the Node is printed.
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offset:
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Initial offset (amount of leading spaces)
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attrnames:
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True if you want to see the attribute names in
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name=value pairs. False to only see the values.
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showemptyattrs:
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False if you want to suppress printing empty attributes.
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nodenames:
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True if you want to see the actual node names
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within their parents.
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showcoord:
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Do you want the coordinates of each Node to be
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displayed.
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"""
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lead = ' ' * offset
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if nodenames and _my_node_name is not None:
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buf.write(lead + self.__class__.__name__+ ' <' + _my_node_name + '>: ')
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else:
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buf.write(lead + self.__class__.__name__+ ': ')
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if self.attr_names:
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def is_empty(v):
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return v is None or (hasattr(v, '__len__') and len(v) == 0)
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nvlist = [(n, getattr(self,n)) for n in self.attr_names \
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if showemptyattrs or not is_empty(getattr(self,n))]
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if attrnames:
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attrstr = ', '.join(f'{name}={value}' for name, value in nvlist)
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else:
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attrstr = ', '.join(f'{value}' for _, value in nvlist)
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buf.write(attrstr)
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if showcoord:
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buf.write(f' (at {self.coord})')
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buf.write('\n')
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for (child_name, child) in self.children():
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child.show(
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buf,
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offset=offset + 2,
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attrnames=attrnames,
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showemptyattrs=showemptyattrs,
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nodenames=nodenames,
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showcoord=showcoord,
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_my_node_name=child_name)
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class NodeVisitor:
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""" A base NodeVisitor class for visiting c_ast nodes.
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Subclass it and define your own visit_XXX methods, where
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XXX is the class name you want to visit with these
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methods.
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For example:
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class ConstantVisitor(NodeVisitor):
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def __init__(self):
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self.values = []
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def visit_Constant(self, node):
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self.values.append(node.value)
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Creates a list of values of all the constant nodes
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encountered below the given node. To use it:
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cv = ConstantVisitor()
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cv.visit(node)
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Notes:
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* generic_visit() will be called for AST nodes for which
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no visit_XXX method was defined.
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* The children of nodes for which a visit_XXX was
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defined will not be visited - if you need this, call
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generic_visit() on the node.
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You can use:
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NodeVisitor.generic_visit(self, node)
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* Modeled after Python's own AST visiting facilities
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(the ast module of Python 3.0)
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"""
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_method_cache = None
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def visit(self, node: Node):
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""" Visit a node.
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"""
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if self._method_cache is None:
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self._method_cache = {}
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visitor = self._method_cache.get(node.__class__.__name__, None)
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if visitor is None:
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method = 'visit_' + node.__class__.__name__
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visitor = getattr(self, method, self.generic_visit)
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self._method_cache[node.__class__.__name__] = visitor
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return visitor(node)
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def generic_visit(self, node: Node):
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""" Called if no explicit visitor function exists for a
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node. Implements preorder visiting of the node.
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"""
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for _, c in node.children():
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self.visit(c)
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'''
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if __name__ == "__main__":
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base_dir = os.path.dirname(os.path.abspath(__file__))
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cfg_path = os.path.join(base_dir, "_c_ast.cfg")
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out_path = os.path.join(base_dir, "c_ast.py")
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ast_gen = ASTCodeGenerator(cfg_path)
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with open(out_path, "w") as out:
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ast_gen.generate(out)
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