import token from typing import Any, Dict, Optional, IO, Text, Tuple from pegen.grammar import ( Cut, GrammarVisitor, NameLeaf, StringLeaf, Rhs, NamedItem, Lookahead, PositiveLookahead, NegativeLookahead, Opt, Repeat0, Repeat1, Gather, Group, Rule, Alt, ) from pegen import grammar from pegen.parser_generator import ParserGenerator MODULE_PREFIX = """\ #!/usr/bin/env python3.8 # @generated by pegen from {filename} import ast import sys import tokenize from typing import Any, Optional from pegen.parser import memoize, memoize_left_rec, logger, Parser """ MODULE_SUFFIX = """ if __name__ == '__main__': from pegen.parser import simple_parser_main simple_parser_main(GeneratedParser) """ class PythonCallMakerVisitor(GrammarVisitor): def __init__(self, parser_generator: ParserGenerator): self.gen = parser_generator self.cache: Dict[Any, Any] = {} def visit_NameLeaf(self, node: NameLeaf) -> Tuple[Optional[str], str]: name = node.value if name in ("NAME", "NUMBER", "STRING", "OP"): name = name.lower() return name, f"self.{name}()" if name in ("NEWLINE", "DEDENT", "INDENT", "ENDMARKER", "ASYNC", "AWAIT"): return name.lower(), f"self.expect({name!r})" return name, f"self.{name}()" def visit_StringLeaf(self, node: StringLeaf) -> Tuple[str, str]: return "literal", f"self.expect({node.value})" def visit_Rhs(self, node: Rhs) -> Tuple[Optional[str], str]: if node in self.cache: return self.cache[node] if len(node.alts) == 1 and len(node.alts[0].items) == 1: self.cache[node] = self.visit(node.alts[0].items[0]) else: name = self.gen.name_node(node) self.cache[node] = name, f"self.{name}()" return self.cache[node] def visit_NamedItem(self, node: NamedItem) -> Tuple[Optional[str], str]: name, call = self.visit(node.item) if node.name: name = node.name return name, call def lookahead_call_helper(self, node: Lookahead) -> Tuple[str, str]: name, call = self.visit(node.node) head, tail = call.split("(", 1) assert tail[-1] == ")" tail = tail[:-1] return head, tail def visit_PositiveLookahead(self, node: PositiveLookahead) -> Tuple[None, str]: head, tail = self.lookahead_call_helper(node) return None, f"self.positive_lookahead({head}, {tail})" def visit_NegativeLookahead(self, node: NegativeLookahead) -> Tuple[None, str]: head, tail = self.lookahead_call_helper(node) return None, f"self.negative_lookahead({head}, {tail})" def visit_Opt(self, node: Opt) -> Tuple[str, str]: name, call = self.visit(node.node) # Note trailing comma (the call may already have one comma # at the end, for example when rules have both repeat0 and optional # markers, e.g: [rule*]) if call.endswith(","): return "opt", call else: return "opt", f"{call}," def visit_Repeat0(self, node: Repeat0) -> Tuple[str, str]: if node in self.cache: return self.cache[node] name = self.gen.name_loop(node.node, False) self.cache[node] = name, f"self.{name}()," # Also a trailing comma! return self.cache[node] def visit_Repeat1(self, node: Repeat1) -> Tuple[str, str]: if node in self.cache: return self.cache[node] name = self.gen.name_loop(node.node, True) self.cache[node] = name, f"self.{name}()" # But no trailing comma here! return self.cache[node] def visit_Gather(self, node: Gather) -> Tuple[str, str]: if node in self.cache: return self.cache[node] name = self.gen.name_gather(node) self.cache[node] = name, f"self.{name}()" # No trailing comma here either! return self.cache[node] def visit_Group(self, node: Group) -> Tuple[Optional[str], str]: return self.visit(node.rhs) def visit_Cut(self, node: Cut) -> Tuple[str, str]: return "cut", "True" class PythonParserGenerator(ParserGenerator, GrammarVisitor): def __init__( self, grammar: grammar.Grammar, file: Optional[IO[Text]], tokens: Dict[int, str] = token.tok_name, ): super().__init__(grammar, tokens, file) self.callmakervisitor = PythonCallMakerVisitor(self) def generate(self, filename: str) -> None: header = self.grammar.metas.get("header", MODULE_PREFIX) if header is not None: self.print(header.rstrip("\n").format(filename=filename)) subheader = self.grammar.metas.get("subheader", "") if subheader: self.print(subheader.format(filename=filename)) self.print("class GeneratedParser(Parser):") while self.todo: for rulename, rule in list(self.todo.items()): del self.todo[rulename] self.print() with self.indent(): self.visit(rule) trailer = self.grammar.metas.get("trailer", MODULE_SUFFIX) if trailer is not None: self.print(trailer.rstrip("\n")) def visit_Rule(self, node: Rule) -> None: is_loop = node.is_loop() is_gather = node.is_gather() rhs = node.flatten() if node.left_recursive: if node.leader: self.print("@memoize_left_rec") else: # Non-leader rules in a cycle are not memoized, # but they must still be logged. self.print("@logger") else: self.print("@memoize") node_type = node.type or "Any" self.print(f"def {node.name}(self) -> Optional[{node_type}]:") with self.indent(): self.print(f"# {node.name}: {rhs}") if node.nullable: self.print(f"# nullable={node.nullable}") self.print("mark = self.mark()") if is_loop: self.print("children = []") self.visit(rhs, is_loop=is_loop, is_gather=is_gather) if is_loop: self.print("return children") else: self.print("return None") def visit_NamedItem(self, node: NamedItem) -> None: name, call = self.callmakervisitor.visit(node.item) if node.name: name = node.name if not name: self.print(call) else: if name != "cut": name = self.dedupe(name) self.print(f"({name} := {call})") def visit_Rhs(self, node: Rhs, is_loop: bool = False, is_gather: bool = False) -> None: if is_loop: assert len(node.alts) == 1 for alt in node.alts: self.visit(alt, is_loop=is_loop, is_gather=is_gather) def visit_Alt(self, node: Alt, is_loop: bool, is_gather: bool) -> None: with self.local_variable_context(): self.print("cut = False") # TODO: Only if needed. if is_loop: self.print("while (") else: self.print("if (") with self.indent(): first = True for item in node.items: if first: first = False else: self.print("and") self.visit(item) if is_gather: self.print("is not None") self.print("):") with self.indent(): action = node.action if not action: if is_gather: assert len(self.local_variable_names) == 2 action = ( f"[{self.local_variable_names[0]}] + {self.local_variable_names[1]}" ) else: action = f"[{', '.join(self.local_variable_names)}]" if is_loop: self.print(f"children.append({action})") self.print(f"mark = self.mark()") else: self.print(f"return {action}") self.print("self.reset(mark)") # Skip remaining alternatives if a cut was reached. self.print("if cut: return None") # TODO: Only if needed.