| r"""Evaluate match expressions, as used by `-k` and `-m`. |
| |
| The grammar is: |
| |
| expression: expr? EOF |
| expr: and_expr ('or' and_expr)* |
| and_expr: not_expr ('and' not_expr)* |
| not_expr: 'not' not_expr | '(' expr ')' | ident kwargs? |
| |
| ident: (\w|:|\+|-|\.|\[|\]|\\|/)+ |
| kwargs: ('(' name '=' value ( ', ' name '=' value )* ')') |
| name: a valid ident, but not a reserved keyword |
| value: (unescaped) string literal | (-)?[0-9]+ | 'False' | 'True' | 'None' |
| |
| The semantics are: |
| |
| - Empty expression evaluates to False. |
| - ident evaluates to True or False according to a provided matcher function. |
| - or/and/not evaluate according to the usual boolean semantics. |
| - ident with parentheses and keyword arguments evaluates to True or False according to a provided matcher function. |
| """ |
|
|
| from __future__ import annotations |
|
|
| import ast |
| from collections.abc import Iterator |
| from collections.abc import Mapping |
| from collections.abc import Sequence |
| import dataclasses |
| import enum |
| import keyword |
| import re |
| import types |
| from typing import Literal |
| from typing import NoReturn |
| from typing import overload |
| from typing import Protocol |
|
|
|
|
| __all__ = [ |
| "Expression", |
| "ParseError", |
| ] |
|
|
|
|
| class TokenType(enum.Enum): |
| LPAREN = "left parenthesis" |
| RPAREN = "right parenthesis" |
| OR = "or" |
| AND = "and" |
| NOT = "not" |
| IDENT = "identifier" |
| EOF = "end of input" |
| EQUAL = "=" |
| STRING = "string literal" |
| COMMA = "," |
|
|
|
|
| @dataclasses.dataclass(frozen=True) |
| class Token: |
| __slots__ = ("pos", "type", "value") |
| type: TokenType |
| value: str |
| pos: int |
|
|
|
|
| class ParseError(Exception): |
| """The expression contains invalid syntax. |
| |
| :param column: The column in the line where the error occurred (1-based). |
| :param message: A description of the error. |
| """ |
|
|
| def __init__(self, column: int, message: str) -> None: |
| self.column = column |
| self.message = message |
|
|
| def __str__(self) -> str: |
| return f"at column {self.column}: {self.message}" |
|
|
|
|
| class Scanner: |
| __slots__ = ("current", "tokens") |
|
|
| def __init__(self, input: str) -> None: |
| self.tokens = self.lex(input) |
| self.current = next(self.tokens) |
|
|
| def lex(self, input: str) -> Iterator[Token]: |
| pos = 0 |
| while pos < len(input): |
| if input[pos] in (" ", "\t"): |
| pos += 1 |
| elif input[pos] == "(": |
| yield Token(TokenType.LPAREN, "(", pos) |
| pos += 1 |
| elif input[pos] == ")": |
| yield Token(TokenType.RPAREN, ")", pos) |
| pos += 1 |
| elif input[pos] == "=": |
| yield Token(TokenType.EQUAL, "=", pos) |
| pos += 1 |
| elif input[pos] == ",": |
| yield Token(TokenType.COMMA, ",", pos) |
| pos += 1 |
| elif (quote_char := input[pos]) in ("'", '"'): |
| end_quote_pos = input.find(quote_char, pos + 1) |
| if end_quote_pos == -1: |
| raise ParseError( |
| pos + 1, |
| f'closing quote "{quote_char}" is missing', |
| ) |
| value = input[pos : end_quote_pos + 1] |
| if (backslash_pos := input.find("\\")) != -1: |
| raise ParseError( |
| backslash_pos + 1, |
| r'escaping with "\" not supported in marker expression', |
| ) |
| yield Token(TokenType.STRING, value, pos) |
| pos += len(value) |
| else: |
| match = re.match(r"(:?\w|:|\+|-|\.|\[|\]|\\|/)+", input[pos:]) |
| if match: |
| value = match.group(0) |
| if value == "or": |
| yield Token(TokenType.OR, value, pos) |
| elif value == "and": |
| yield Token(TokenType.AND, value, pos) |
| elif value == "not": |
| yield Token(TokenType.NOT, value, pos) |
| else: |
| yield Token(TokenType.IDENT, value, pos) |
| pos += len(value) |
| else: |
| raise ParseError( |
| pos + 1, |
| f'unexpected character "{input[pos]}"', |
| ) |
| yield Token(TokenType.EOF, "", pos) |
|
|
| @overload |
| def accept(self, type: TokenType, *, reject: Literal[True]) -> Token: ... |
|
|
| @overload |
| def accept( |
| self, type: TokenType, *, reject: Literal[False] = False |
| ) -> Token | None: ... |
|
|
| def accept(self, type: TokenType, *, reject: bool = False) -> Token | None: |
| if self.current.type is type: |
| token = self.current |
| if token.type is not TokenType.EOF: |
| self.current = next(self.tokens) |
| return token |
| if reject: |
| self.reject((type,)) |
| return None |
|
|
| def reject(self, expected: Sequence[TokenType]) -> NoReturn: |
| raise ParseError( |
| self.current.pos + 1, |
| "expected {}; got {}".format( |
| " OR ".join(type.value for type in expected), |
| self.current.type.value, |
| ), |
| ) |
|
|
|
|
| |
| |
| |
| IDENT_PREFIX = "$" |
|
|
|
|
| def expression(s: Scanner) -> ast.Expression: |
| if s.accept(TokenType.EOF): |
| ret: ast.expr = ast.Constant(False) |
| else: |
| ret = expr(s) |
| s.accept(TokenType.EOF, reject=True) |
| return ast.fix_missing_locations(ast.Expression(ret)) |
|
|
|
|
| def expr(s: Scanner) -> ast.expr: |
| ret = and_expr(s) |
| while s.accept(TokenType.OR): |
| rhs = and_expr(s) |
| ret = ast.BoolOp(ast.Or(), [ret, rhs]) |
| return ret |
|
|
|
|
| def and_expr(s: Scanner) -> ast.expr: |
| ret = not_expr(s) |
| while s.accept(TokenType.AND): |
| rhs = not_expr(s) |
| ret = ast.BoolOp(ast.And(), [ret, rhs]) |
| return ret |
|
|
|
|
| def not_expr(s: Scanner) -> ast.expr: |
| if s.accept(TokenType.NOT): |
| return ast.UnaryOp(ast.Not(), not_expr(s)) |
| if s.accept(TokenType.LPAREN): |
| ret = expr(s) |
| s.accept(TokenType.RPAREN, reject=True) |
| return ret |
| ident = s.accept(TokenType.IDENT) |
| if ident: |
| name = ast.Name(IDENT_PREFIX + ident.value, ast.Load()) |
| if s.accept(TokenType.LPAREN): |
| ret = ast.Call(func=name, args=[], keywords=all_kwargs(s)) |
| s.accept(TokenType.RPAREN, reject=True) |
| else: |
| ret = name |
| return ret |
|
|
| s.reject((TokenType.NOT, TokenType.LPAREN, TokenType.IDENT)) |
|
|
|
|
| BUILTIN_MATCHERS = {"True": True, "False": False, "None": None} |
|
|
|
|
| def single_kwarg(s: Scanner) -> ast.keyword: |
| keyword_name = s.accept(TokenType.IDENT, reject=True) |
| if not keyword_name.value.isidentifier(): |
| raise ParseError( |
| keyword_name.pos + 1, |
| f"not a valid python identifier {keyword_name.value}", |
| ) |
| if keyword.iskeyword(keyword_name.value): |
| raise ParseError( |
| keyword_name.pos + 1, |
| f"unexpected reserved python keyword `{keyword_name.value}`", |
| ) |
| s.accept(TokenType.EQUAL, reject=True) |
|
|
| if value_token := s.accept(TokenType.STRING): |
| value: str | int | bool | None = value_token.value[1:-1] |
| else: |
| value_token = s.accept(TokenType.IDENT, reject=True) |
| if (number := value_token.value).isdigit() or ( |
| number.startswith("-") and number[1:].isdigit() |
| ): |
| value = int(number) |
| elif value_token.value in BUILTIN_MATCHERS: |
| value = BUILTIN_MATCHERS[value_token.value] |
| else: |
| raise ParseError( |
| value_token.pos + 1, |
| f'unexpected character/s "{value_token.value}"', |
| ) |
|
|
| ret = ast.keyword(keyword_name.value, ast.Constant(value)) |
| return ret |
|
|
|
|
| def all_kwargs(s: Scanner) -> list[ast.keyword]: |
| ret = [single_kwarg(s)] |
| while s.accept(TokenType.COMMA): |
| ret.append(single_kwarg(s)) |
| return ret |
|
|
|
|
| class MatcherCall(Protocol): |
| def __call__(self, name: str, /, **kwargs: str | int | bool | None) -> bool: ... |
|
|
|
|
| @dataclasses.dataclass |
| class MatcherNameAdapter: |
| matcher: MatcherCall |
| name: str |
|
|
| def __bool__(self) -> bool: |
| return self.matcher(self.name) |
|
|
| def __call__(self, **kwargs: str | int | bool | None) -> bool: |
| return self.matcher(self.name, **kwargs) |
|
|
|
|
| class MatcherAdapter(Mapping[str, MatcherNameAdapter]): |
| """Adapts a matcher function to a locals mapping as required by eval().""" |
|
|
| def __init__(self, matcher: MatcherCall) -> None: |
| self.matcher = matcher |
|
|
| def __getitem__(self, key: str) -> MatcherNameAdapter: |
| return MatcherNameAdapter(matcher=self.matcher, name=key[len(IDENT_PREFIX) :]) |
|
|
| def __iter__(self) -> Iterator[str]: |
| raise NotImplementedError() |
|
|
| def __len__(self) -> int: |
| raise NotImplementedError() |
|
|
|
|
| class Expression: |
| """A compiled match expression as used by -k and -m. |
| |
| The expression can be evaluated against different matchers. |
| """ |
|
|
| __slots__ = ("code",) |
|
|
| def __init__(self, code: types.CodeType) -> None: |
| self.code = code |
|
|
| @classmethod |
| def compile(cls, input: str) -> Expression: |
| """Compile a match expression. |
| |
| :param input: The input expression - one line. |
| """ |
| astexpr = expression(Scanner(input)) |
| code: types.CodeType = compile( |
| astexpr, |
| filename="<pytest match expression>", |
| mode="eval", |
| ) |
| return Expression(code) |
|
|
| def evaluate(self, matcher: MatcherCall) -> bool: |
| """Evaluate the match expression. |
| |
| :param matcher: |
| Given an identifier, should return whether it matches or not. |
| Should be prepared to handle arbitrary strings as input. |
| |
| :returns: Whether the expression matches or not. |
| """ |
| ret: bool = bool(eval(self.code, {"__builtins__": {}}, MatcherAdapter(matcher))) |
| return ret |
|
|
