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Mini Shell
Mini Shell
"""Handwritten parser of dependency specifiers.
The docstring for each __parse_* function contains EBNF-inspired grammar representing
the implementation.
"""
from __future__ import annotations
import ast
from typing import NamedTuple, Sequence, Tuple, Union
from ._tokenizer import DEFAULT_RULES, Tokenizer
class Node:
def __init__(self, value: str) -> None:
self.value = value
def __str__(self) -> str:
return self.value
def __repr__(self) -> str:
return f"<{self.__class__.__name__}('{self}')>"
def serialize(self) -> str:
raise NotImplementedError
class Variable(Node):
def serialize(self) -> str:
return str(self)
class Value(Node):
def serialize(self) -> str:
return f'"{self}"'
class Op(Node):
def serialize(self) -> str:
return str(self)
MarkerVar = Union[Variable, Value]
MarkerItem = Tuple[MarkerVar, Op, MarkerVar]
MarkerAtom = Union[MarkerItem, Sequence["MarkerAtom"]]
MarkerList = Sequence[Union["MarkerList", MarkerAtom, str]]
class ParsedRequirement(NamedTuple):
name: str
url: str
extras: list[str]
specifier: str
marker: MarkerList | None
# --------------------------------------------------------------------------------------
# Recursive descent parser for dependency specifier
# --------------------------------------------------------------------------------------
def parse_requirement(source: str) -> ParsedRequirement:
return _parse_requirement(Tokenizer(source, rules=DEFAULT_RULES))
def _parse_requirement(tokenizer: Tokenizer) -> ParsedRequirement:
"""
requirement = WS? IDENTIFIER WS? extras WS? requirement_details
"""
tokenizer.consume("WS")
name_token = tokenizer.expect(
"IDENTIFIER", expected="package name at the start of dependency specifier"
)
name = name_token.text
tokenizer.consume("WS")
extras = _parse_extras(tokenizer)
tokenizer.consume("WS")
url, specifier, marker = _parse_requirement_details(tokenizer)
tokenizer.expect("END", expected="end of dependency specifier")
return ParsedRequirement(name, url, extras, specifier, marker)
def _parse_requirement_details(
tokenizer: Tokenizer,
) -> tuple[str, str, MarkerList | None]:
"""
requirement_details = AT URL (WS requirement_marker?)?
| specifier WS? (requirement_marker)?
"""
specifier = ""
url = ""
marker = None
if tokenizer.check("AT"):
tokenizer.read()
tokenizer.consume("WS")
url_start = tokenizer.position
url = tokenizer.expect("URL", expected="URL after @").text
if tokenizer.check("END", peek=True):
return (url, specifier, marker)
tokenizer.expect("WS", expected="whitespace after URL")
# The input might end after whitespace.
if tokenizer.check("END", peek=True):
return (url, specifier, marker)
marker = _parse_requirement_marker(
tokenizer, span_start=url_start, after="URL and whitespace"
)
else:
specifier_start = tokenizer.position
specifier = _parse_specifier(tokenizer)
tokenizer.consume("WS")
if tokenizer.check("END", peek=True):
return (url, specifier, marker)
marker = _parse_requirement_marker(
tokenizer,
span_start=specifier_start,
after=(
"version specifier"
if specifier
else "name and no valid version specifier"
),
)
return (url, specifier, marker)
def _parse_requirement_marker(
tokenizer: Tokenizer, *, span_start: int, after: str
) -> MarkerList:
"""
requirement_marker = SEMICOLON marker WS?
"""
if not tokenizer.check("SEMICOLON"):
tokenizer.raise_syntax_error(
f"Expected end or semicolon (after {after})",
span_start=span_start,
)
tokenizer.read()
marker = _parse_marker(tokenizer)
tokenizer.consume("WS")
return marker
def _parse_extras(tokenizer: Tokenizer) -> list[str]:
"""
extras = (LEFT_BRACKET wsp* extras_list? wsp* RIGHT_BRACKET)?
"""
if not tokenizer.check("LEFT_BRACKET", peek=True):
return []
with tokenizer.enclosing_tokens(
"LEFT_BRACKET",
"RIGHT_BRACKET",
around="extras",
):
tokenizer.consume("WS")
extras = _parse_extras_list(tokenizer)
tokenizer.consume("WS")
return extras
def _parse_extras_list(tokenizer: Tokenizer) -> list[str]:
"""
extras_list = identifier (wsp* ',' wsp* identifier)*
"""
extras: list[str] = []
if not tokenizer.check("IDENTIFIER"):
return extras
extras.append(tokenizer.read().text)
while True:
tokenizer.consume("WS")
if tokenizer.check("IDENTIFIER", peek=True):
tokenizer.raise_syntax_error("Expected comma between extra names")
elif not tokenizer.check("COMMA"):
break
tokenizer.read()
tokenizer.consume("WS")
extra_token = tokenizer.expect("IDENTIFIER", expected="extra name after comma")
extras.append(extra_token.text)
return extras
def _parse_specifier(tokenizer: Tokenizer) -> str:
"""
specifier = LEFT_PARENTHESIS WS? version_many WS? RIGHT_PARENTHESIS
| WS? version_many WS?
"""
with tokenizer.enclosing_tokens(
"LEFT_PARENTHESIS",
"RIGHT_PARENTHESIS",
around="version specifier",
):
tokenizer.consume("WS")
parsed_specifiers = _parse_version_many(tokenizer)
tokenizer.consume("WS")
return parsed_specifiers
def _parse_version_many(tokenizer: Tokenizer) -> str:
"""
version_many = (SPECIFIER (WS? COMMA WS? SPECIFIER)*)?
"""
parsed_specifiers = ""
while tokenizer.check("SPECIFIER"):
span_start = tokenizer.position
parsed_specifiers += tokenizer.read().text
if tokenizer.check("VERSION_PREFIX_TRAIL", peek=True):
tokenizer.raise_syntax_error(
".* suffix can only be used with `==` or `!=` operators",
span_start=span_start,
span_end=tokenizer.position + 1,
)
if tokenizer.check("VERSION_LOCAL_LABEL_TRAIL", peek=True):
tokenizer.raise_syntax_error(
"Local version label can only be used with `==` or `!=` operators",
span_start=span_start,
span_end=tokenizer.position,
)
tokenizer.consume("WS")
if not tokenizer.check("COMMA"):
break
parsed_specifiers += tokenizer.read().text
tokenizer.consume("WS")
return parsed_specifiers
# --------------------------------------------------------------------------------------
# Recursive descent parser for marker expression
# --------------------------------------------------------------------------------------
def parse_marker(source: str) -> MarkerList:
return _parse_full_marker(Tokenizer(source, rules=DEFAULT_RULES))
def _parse_full_marker(tokenizer: Tokenizer) -> MarkerList:
retval = _parse_marker(tokenizer)
tokenizer.expect("END", expected="end of marker expression")
return retval
def _parse_marker(tokenizer: Tokenizer) -> MarkerList:
"""
marker = marker_atom (BOOLOP marker_atom)+
"""
expression = [_parse_marker_atom(tokenizer)]
while tokenizer.check("BOOLOP"):
token = tokenizer.read()
expr_right = _parse_marker_atom(tokenizer)
expression.extend((token.text, expr_right))
return expression
def _parse_marker_atom(tokenizer: Tokenizer) -> MarkerAtom:
"""
marker_atom = WS? LEFT_PARENTHESIS WS? marker WS? RIGHT_PARENTHESIS WS?
| WS? marker_item WS?
"""
tokenizer.consume("WS")
if tokenizer.check("LEFT_PARENTHESIS", peek=True):
with tokenizer.enclosing_tokens(
"LEFT_PARENTHESIS",
"RIGHT_PARENTHESIS",
around="marker expression",
):
tokenizer.consume("WS")
marker: MarkerAtom = _parse_marker(tokenizer)
tokenizer.consume("WS")
else:
marker = _parse_marker_item(tokenizer)
tokenizer.consume("WS")
return marker
def _parse_marker_item(tokenizer: Tokenizer) -> MarkerItem:
"""
marker_item = WS? marker_var WS? marker_op WS? marker_var WS?
"""
tokenizer.consume("WS")
marker_var_left = _parse_marker_var(tokenizer)
tokenizer.consume("WS")
marker_op = _parse_marker_op(tokenizer)
tokenizer.consume("WS")
marker_var_right = _parse_marker_var(tokenizer)
tokenizer.consume("WS")
return (marker_var_left, marker_op, marker_var_right)
def _parse_marker_var(tokenizer: Tokenizer) -> MarkerVar:
"""
marker_var = VARIABLE | QUOTED_STRING
"""
if tokenizer.check("VARIABLE"):
return process_env_var(tokenizer.read().text.replace(".", "_"))
elif tokenizer.check("QUOTED_STRING"):
return process_python_str(tokenizer.read().text)
else:
tokenizer.raise_syntax_error(
message="Expected a marker variable or quoted string"
)
def process_env_var(env_var: str) -> Variable:
if env_var in ("platform_python_implementation", "python_implementation"):
return Variable("platform_python_implementation")
else:
return Variable(env_var)
def process_python_str(python_str: str) -> Value:
value = ast.literal_eval(python_str)
return Value(str(value))
def _parse_marker_op(tokenizer: Tokenizer) -> Op:
"""
marker_op = IN | NOT IN | OP
"""
if tokenizer.check("IN"):
tokenizer.read()
return Op("in")
elif tokenizer.check("NOT"):
tokenizer.read()
tokenizer.expect("WS", expected="whitespace after 'not'")
tokenizer.expect("IN", expected="'in' after 'not'")
return Op("not in")
elif tokenizer.check("OP"):
return Op(tokenizer.read().text)
else:
return tokenizer.raise_syntax_error(
"Expected marker operator, one of "
"<=, <, !=, ==, >=, >, ~=, ===, in, not in"
)
Zerion Mini Shell 1.0