355 lines
10 KiB
Python
355 lines
10 KiB
Python
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"""Handwritten parser of dependency specifiers.
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The docstring for each __parse_* function contains EBNF-inspired grammar representing
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the implementation.
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"""
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from __future__ import annotations
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import ast
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from typing import NamedTuple, Sequence, Tuple, Union
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from ._tokenizer import DEFAULT_RULES, Tokenizer
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class Node:
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def __init__(self, value: str) -> None:
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self.value = value
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def __str__(self) -> str:
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return self.value
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def __repr__(self) -> str:
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return f"<{self.__class__.__name__}('{self}')>"
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def serialize(self) -> str:
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raise NotImplementedError
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class Variable(Node):
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def serialize(self) -> str:
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return str(self)
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class Value(Node):
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def serialize(self) -> str:
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return f'"{self}"'
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class Op(Node):
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def serialize(self) -> str:
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return str(self)
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MarkerVar = Union[Variable, Value]
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MarkerItem = Tuple[MarkerVar, Op, MarkerVar]
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MarkerAtom = Union[MarkerItem, Sequence["MarkerAtom"]]
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MarkerList = Sequence[Union["MarkerList", MarkerAtom, str]]
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class ParsedRequirement(NamedTuple):
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name: str
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url: str
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extras: list[str]
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specifier: str
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marker: MarkerList | None
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# --------------------------------------------------------------------------------------
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# Recursive descent parser for dependency specifier
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# --------------------------------------------------------------------------------------
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def parse_requirement(source: str) -> ParsedRequirement:
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return _parse_requirement(Tokenizer(source, rules=DEFAULT_RULES))
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def _parse_requirement(tokenizer: Tokenizer) -> ParsedRequirement:
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"""
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requirement = WS? IDENTIFIER WS? extras WS? requirement_details
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"""
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tokenizer.consume("WS")
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name_token = tokenizer.expect(
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"IDENTIFIER", expected="package name at the start of dependency specifier"
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)
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name = name_token.text
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tokenizer.consume("WS")
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extras = _parse_extras(tokenizer)
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tokenizer.consume("WS")
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url, specifier, marker = _parse_requirement_details(tokenizer)
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tokenizer.expect("END", expected="end of dependency specifier")
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return ParsedRequirement(name, url, extras, specifier, marker)
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def _parse_requirement_details(
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tokenizer: Tokenizer,
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) -> tuple[str, str, MarkerList | None]:
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"""
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requirement_details = AT URL (WS requirement_marker?)?
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| specifier WS? (requirement_marker)?
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"""
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specifier = ""
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url = ""
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marker = None
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if tokenizer.check("AT"):
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tokenizer.read()
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tokenizer.consume("WS")
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url_start = tokenizer.position
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url = tokenizer.expect("URL", expected="URL after @").text
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if tokenizer.check("END", peek=True):
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return (url, specifier, marker)
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tokenizer.expect("WS", expected="whitespace after URL")
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# The input might end after whitespace.
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if tokenizer.check("END", peek=True):
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return (url, specifier, marker)
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marker = _parse_requirement_marker(
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tokenizer, span_start=url_start, after="URL and whitespace"
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)
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else:
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specifier_start = tokenizer.position
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specifier = _parse_specifier(tokenizer)
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tokenizer.consume("WS")
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if tokenizer.check("END", peek=True):
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return (url, specifier, marker)
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marker = _parse_requirement_marker(
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tokenizer,
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span_start=specifier_start,
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after=(
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"version specifier"
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if specifier
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else "name and no valid version specifier"
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),
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)
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return (url, specifier, marker)
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def _parse_requirement_marker(
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tokenizer: Tokenizer, *, span_start: int, after: str
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) -> MarkerList:
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"""
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requirement_marker = SEMICOLON marker WS?
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"""
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if not tokenizer.check("SEMICOLON"):
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tokenizer.raise_syntax_error(
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f"Expected end or semicolon (after {after})",
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span_start=span_start,
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)
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tokenizer.read()
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marker = _parse_marker(tokenizer)
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tokenizer.consume("WS")
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return marker
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def _parse_extras(tokenizer: Tokenizer) -> list[str]:
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"""
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extras = (LEFT_BRACKET wsp* extras_list? wsp* RIGHT_BRACKET)?
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"""
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if not tokenizer.check("LEFT_BRACKET", peek=True):
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return []
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with tokenizer.enclosing_tokens(
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"LEFT_BRACKET",
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"RIGHT_BRACKET",
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around="extras",
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):
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tokenizer.consume("WS")
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extras = _parse_extras_list(tokenizer)
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tokenizer.consume("WS")
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return extras
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def _parse_extras_list(tokenizer: Tokenizer) -> list[str]:
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"""
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extras_list = identifier (wsp* ',' wsp* identifier)*
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"""
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extras: list[str] = []
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if not tokenizer.check("IDENTIFIER"):
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return extras
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extras.append(tokenizer.read().text)
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while True:
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tokenizer.consume("WS")
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if tokenizer.check("IDENTIFIER", peek=True):
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tokenizer.raise_syntax_error("Expected comma between extra names")
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elif not tokenizer.check("COMMA"):
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break
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tokenizer.read()
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tokenizer.consume("WS")
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extra_token = tokenizer.expect("IDENTIFIER", expected="extra name after comma")
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extras.append(extra_token.text)
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return extras
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def _parse_specifier(tokenizer: Tokenizer) -> str:
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"""
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specifier = LEFT_PARENTHESIS WS? version_many WS? RIGHT_PARENTHESIS
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| WS? version_many WS?
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"""
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with tokenizer.enclosing_tokens(
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"LEFT_PARENTHESIS",
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"RIGHT_PARENTHESIS",
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around="version specifier",
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):
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tokenizer.consume("WS")
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parsed_specifiers = _parse_version_many(tokenizer)
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tokenizer.consume("WS")
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return parsed_specifiers
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def _parse_version_many(tokenizer: Tokenizer) -> str:
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"""
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version_many = (SPECIFIER (WS? COMMA WS? SPECIFIER)*)?
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"""
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parsed_specifiers = ""
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while tokenizer.check("SPECIFIER"):
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span_start = tokenizer.position
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parsed_specifiers += tokenizer.read().text
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if tokenizer.check("VERSION_PREFIX_TRAIL", peek=True):
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tokenizer.raise_syntax_error(
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".* suffix can only be used with `==` or `!=` operators",
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span_start=span_start,
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span_end=tokenizer.position + 1,
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)
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if tokenizer.check("VERSION_LOCAL_LABEL_TRAIL", peek=True):
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tokenizer.raise_syntax_error(
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"Local version label can only be used with `==` or `!=` operators",
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span_start=span_start,
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span_end=tokenizer.position,
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)
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tokenizer.consume("WS")
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if not tokenizer.check("COMMA"):
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break
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parsed_specifiers += tokenizer.read().text
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tokenizer.consume("WS")
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return parsed_specifiers
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# --------------------------------------------------------------------------------------
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# Recursive descent parser for marker expression
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# --------------------------------------------------------------------------------------
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def parse_marker(source: str) -> MarkerList:
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return _parse_full_marker(Tokenizer(source, rules=DEFAULT_RULES))
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def _parse_full_marker(tokenizer: Tokenizer) -> MarkerList:
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retval = _parse_marker(tokenizer)
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tokenizer.expect("END", expected="end of marker expression")
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return retval
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def _parse_marker(tokenizer: Tokenizer) -> MarkerList:
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"""
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marker = marker_atom (BOOLOP marker_atom)+
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"""
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expression = [_parse_marker_atom(tokenizer)]
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while tokenizer.check("BOOLOP"):
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token = tokenizer.read()
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expr_right = _parse_marker_atom(tokenizer)
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expression.extend((token.text, expr_right))
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return expression
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def _parse_marker_atom(tokenizer: Tokenizer) -> MarkerAtom:
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"""
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marker_atom = WS? LEFT_PARENTHESIS WS? marker WS? RIGHT_PARENTHESIS WS?
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| WS? marker_item WS?
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"""
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tokenizer.consume("WS")
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if tokenizer.check("LEFT_PARENTHESIS", peek=True):
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with tokenizer.enclosing_tokens(
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"LEFT_PARENTHESIS",
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"RIGHT_PARENTHESIS",
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around="marker expression",
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):
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tokenizer.consume("WS")
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marker: MarkerAtom = _parse_marker(tokenizer)
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tokenizer.consume("WS")
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else:
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marker = _parse_marker_item(tokenizer)
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tokenizer.consume("WS")
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return marker
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def _parse_marker_item(tokenizer: Tokenizer) -> MarkerItem:
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"""
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marker_item = WS? marker_var WS? marker_op WS? marker_var WS?
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"""
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tokenizer.consume("WS")
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marker_var_left = _parse_marker_var(tokenizer)
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tokenizer.consume("WS")
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marker_op = _parse_marker_op(tokenizer)
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tokenizer.consume("WS")
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marker_var_right = _parse_marker_var(tokenizer)
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tokenizer.consume("WS")
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return (marker_var_left, marker_op, marker_var_right)
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def _parse_marker_var(tokenizer: Tokenizer) -> MarkerVar:
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"""
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marker_var = VARIABLE | QUOTED_STRING
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"""
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if tokenizer.check("VARIABLE"):
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return process_env_var(tokenizer.read().text.replace(".", "_"))
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elif tokenizer.check("QUOTED_STRING"):
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return process_python_str(tokenizer.read().text)
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else:
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tokenizer.raise_syntax_error(
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message="Expected a marker variable or quoted string"
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)
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def process_env_var(env_var: str) -> Variable:
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if env_var in ("platform_python_implementation", "python_implementation"):
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return Variable("platform_python_implementation")
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else:
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return Variable(env_var)
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def process_python_str(python_str: str) -> Value:
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value = ast.literal_eval(python_str)
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return Value(str(value))
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def _parse_marker_op(tokenizer: Tokenizer) -> Op:
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"""
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marker_op = IN | NOT IN | OP
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"""
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if tokenizer.check("IN"):
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tokenizer.read()
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return Op("in")
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elif tokenizer.check("NOT"):
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tokenizer.read()
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tokenizer.expect("WS", expected="whitespace after 'not'")
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tokenizer.expect("IN", expected="'in' after 'not'")
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return Op("not in")
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elif tokenizer.check("OP"):
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return Op(tokenizer.read().text)
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else:
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return tokenizer.raise_syntax_error(
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"Expected marker operator, one of "
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"<=, <, !=, ==, >=, >, ~=, ===, in, not in"
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)
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