# SPDX-License-Identifier: BSD-3-Clause # Copyright(c) 2024 Arm Limited """Parsing utility module. This module provides :class:`~TextParser` which can be used to model any dataclass to a block of text. """ import re from abc import ABC from dataclasses import MISSING, dataclass, fields from functools import partial from typing import Any, Callable, TypedDict, cast from typing_extensions import Self from framework.exception import InternalError class ParserFn(TypedDict): """Parser function in a dict compatible with the :func:`dataclasses.field` metadata param.""" #: TextParser_fn: Callable[[str], Any] @dataclass class TextParser(ABC): r"""Helper abstract dataclass that parses a text according to the fields' rules. In order to enable text parsing in a dataclass, subclass it with :class:`TextParser`. The provided `parse` method is a factory which parses the supplied text and creates an instance with populated dataclass fields. This takes text as an argument and for each field in the dataclass, the field's parser function is run against the whole text. The returned value is then assigned to the field of the new instance. If the field does not have a parser function its default value or factory is used instead. If no default is available either, an exception is raised. This class provides a selection of parser functions and a function to wrap parser functions with generic functions. Parser functions are designed to be passed to the fields' metadata param. The most commonly used parser function is expected to be the `find` method, which runs a regular expression against the text to find matches. Example: The following example makes use of and demonstrates every parser function available: .. code:: python from dataclasses import dataclass, field from enum import Enum from framework.parser import TextParser class Colour(Enum): BLACK = 1 WHITE = 2 @classmethod def from_str(cls, text: str): match text: case "black": return cls.BLACK case "white": return cls.WHITE case _: return None # unsupported colour @classmethod def make_parser(cls): # make a parser function that finds a match and # then makes it a Colour object through Colour.from_str return TextParser.wrap(TextParser.find(r"is a (\w+)"), cls.from_str) @dataclass class Animal(TextParser): kind: str = field(metadata=TextParser.find(r"is a \w+ (\w+)")) name: str = field(metadata=TextParser.find(r"^(\w+)")) colour: Colour = field(metadata=Colour.make_parser()) age: int = field(metadata=TextParser.find_int(r"aged (\d+)")) steph = Animal.parse("Stephanie is a white cat aged 10") print(steph) # Animal(kind='cat', name='Stephanie', colour=, age=10) """ """============ BEGIN PARSER FUNCTIONS ============""" @staticmethod def wrap(parser_fn: ParserFn, wrapper_fn: Callable) -> ParserFn: """Makes a wrapped parser function. `parser_fn` is called and if a non-None value is returned, `wrapper_function` is called with it. Otherwise the function returns early with None. In pseudo-code:: intermediate_value := parser_fn(input) if intermediary_value is None then output := None else output := wrapper_fn(intermediate_value) Args: parser_fn: The dictionary storing the parser function to be wrapped. wrapper_fn: The function that wraps `parser_fn`. Returns: ParserFn: A dictionary for the `dataclasses.field` metadata argument containing the newly wrapped parser function. """ inner_fn = parser_fn["TextParser_fn"] def _composite_parser_fn(text: str) -> Any: intermediate_value = inner_fn(text) if intermediate_value is None: return None return wrapper_fn(intermediate_value) return ParserFn(TextParser_fn=_composite_parser_fn) @staticmethod def find( pattern: str | re.Pattern[str], flags: re.RegexFlag = re.RegexFlag(0), named: bool = False, ) -> ParserFn: """Makes a parser function that finds a regular expression match in the text. If the pattern has any capturing groups, it returns None if no match was found, otherwise a tuple containing the values per each group is returned. If the pattern has only one capturing group and a match was found, its value is returned. If the pattern has no capturing groups then either True or False is returned if the pattern had a match or not. Args: pattern: The regular expression pattern. flags: The regular expression flags. Ignored if the given pattern is already compiled. named: If set to True only the named capturing groups will be returned, as a dictionary. Returns: ParserFn: A dictionary for the `dataclasses.field` metadata argument containing the find parser function. """ if isinstance(pattern, str): pattern = re.compile(pattern, flags) def _find(text: str) -> Any: m = pattern.search(text) if m is None: return None if pattern.groups > 0 else False if pattern.groups == 0: return True if named: return m.groupdict() matches = m.groups() if len(matches) == 1: return matches[0] return matches return ParserFn(TextParser_fn=_find) @staticmethod def find_int( pattern: str | re.Pattern[str], flags: re.RegexFlag = re.RegexFlag(0), int_base: int = 0, ) -> ParserFn: """Makes a parser function that converts the match of :meth:`~find` to int. This function is compatible only with a pattern containing one capturing group. Args: pattern: The regular expression pattern. flags: The regular expression flags. Ignored if the given pattern is already compiled. int_base: The base of the number to convert from. Raises: InternalError: If the pattern does not have exactly one capturing group. Returns: ParserFn: A dictionary for the `dataclasses.field` metadata argument containing the :meth:`~find` parser function wrapped by the int built-in. """ if isinstance(pattern, str): pattern = re.compile(pattern, flags) if pattern.groups != 1: raise InternalError("only one capturing group is allowed with this parser function") return TextParser.wrap(TextParser.find(pattern), partial(int, base=int_base)) """============ END PARSER FUNCTIONS ============""" @classmethod def parse(cls, text: str) -> Self: """Creates a new instance of the class from the given text. A new class instance is created with all the fields that have a parser function in their metadata. Fields without one are ignored and are expected to have a default value, otherwise the class initialization will fail. A field is populated with the value returned by its corresponding parser function. Args: text: the text to parse Raises: InternalError: if the parser did not find a match and the field does not have a default value or default factory. Returns: A new instance of the class. """ fields_values = {} for field in fields(cls): parse = cast(ParserFn, field.metadata).get("TextParser_fn") if parse is None: continue value = parse(text) if value is not None: fields_values[field.name] = value elif field.default is MISSING and field.default_factory is MISSING: raise InternalError( f"parser for field {field.name} returned None, but the field has no default" ) return cls(**fields_values)