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Filename : identity.py
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# orm/identity.py
# Copyright (C) 2005-2024 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php

from __future__ import annotations

from typing import Any
from typing import cast
from typing import Dict
from typing import Iterable
from typing import Iterator
from typing import List
from typing import NoReturn
from typing import Optional
from typing import Set
from typing import Tuple
from typing import TYPE_CHECKING
from typing import TypeVar
import weakref

from . import util as orm_util
from .. import exc as sa_exc

if TYPE_CHECKING:
    from ._typing import _IdentityKeyType
    from .state import InstanceState


_T = TypeVar("_T", bound=Any)

_O = TypeVar("_O", bound=object)


class IdentityMap:
    _wr: weakref.ref[IdentityMap]

    _dict: Dict[_IdentityKeyType[Any], Any]
    _modified: Set[InstanceState[Any]]

    def __init__(self) -> None:
        self._dict = {}
        self._modified = set()
        self._wr = weakref.ref(self)

    def _kill(self) -> None:
        self._add_unpresent = _killed  # type: ignore

    def all_states(self) -> List[InstanceState[Any]]:
        raise NotImplementedError()

    def contains_state(self, state: InstanceState[Any]) -> bool:
        raise NotImplementedError()

    def __contains__(self, key: _IdentityKeyType[Any]) -> bool:
        raise NotImplementedError()

    def safe_discard(self, state: InstanceState[Any]) -> None:
        raise NotImplementedError()

    def __getitem__(self, key: _IdentityKeyType[_O]) -> _O:
        raise NotImplementedError()

    def get(
        self, key: _IdentityKeyType[_O], default: Optional[_O] = None
    ) -> Optional[_O]:
        raise NotImplementedError()

    def fast_get_state(
        self, key: _IdentityKeyType[_O]
    ) -> Optional[InstanceState[_O]]:
        raise NotImplementedError()

    def keys(self) -> Iterable[_IdentityKeyType[Any]]:
        return self._dict.keys()

    def values(self) -> Iterable[object]:
        raise NotImplementedError()

    def replace(self, state: InstanceState[_O]) -> Optional[InstanceState[_O]]:
        raise NotImplementedError()

    def add(self, state: InstanceState[Any]) -> bool:
        raise NotImplementedError()

    def _fast_discard(self, state: InstanceState[Any]) -> None:
        raise NotImplementedError()

    def _add_unpresent(
        self, state: InstanceState[Any], key: _IdentityKeyType[Any]
    ) -> None:
        """optional inlined form of add() which can assume item isn't present
        in the map"""
        self.add(state)

    def _manage_incoming_state(self, state: InstanceState[Any]) -> None:
        state._instance_dict = self._wr

        if state.modified:
            self._modified.add(state)

    def _manage_removed_state(self, state: InstanceState[Any]) -> None:
        del state._instance_dict
        if state.modified:
            self._modified.discard(state)

    def _dirty_states(self) -> Set[InstanceState[Any]]:
        return self._modified

    def check_modified(self) -> bool:
        """return True if any InstanceStates present have been marked
        as 'modified'.

        """
        return bool(self._modified)

    def has_key(self, key: _IdentityKeyType[Any]) -> bool:
        return key in self

    def __len__(self) -> int:
        return len(self._dict)


class WeakInstanceDict(IdentityMap):
    _dict: Dict[_IdentityKeyType[Any], InstanceState[Any]]

    def __getitem__(self, key: _IdentityKeyType[_O]) -> _O:
        state = cast("InstanceState[_O]", self._dict[key])
        o = state.obj()
        if o is None:
            raise KeyError(key)
        return o

    def __contains__(self, key: _IdentityKeyType[Any]) -> bool:
        try:
            if key in self._dict:
                state = self._dict[key]
                o = state.obj()
            else:
                return False
        except KeyError:
            return False
        else:
            return o is not None

    def contains_state(self, state: InstanceState[Any]) -> bool:
        if state.key in self._dict:
            if TYPE_CHECKING:
                assert state.key is not None
            try:
                return self._dict[state.key] is state
            except KeyError:
                return False
        else:
            return False

    def replace(
        self, state: InstanceState[Any]
    ) -> Optional[InstanceState[Any]]:
        assert state.key is not None
        if state.key in self._dict:
            try:
                existing = existing_non_none = self._dict[state.key]
            except KeyError:
                # catch gc removed the key after we just checked for it
                existing = None
            else:
                if existing_non_none is not state:
                    self._manage_removed_state(existing_non_none)
                else:
                    return None
        else:
            existing = None

        self._dict[state.key] = state
        self._manage_incoming_state(state)
        return existing

    def add(self, state: InstanceState[Any]) -> bool:
        key = state.key
        assert key is not None
        # inline of self.__contains__
        if key in self._dict:
            try:
                existing_state = self._dict[key]
            except KeyError:
                # catch gc removed the key after we just checked for it
                pass
            else:
                if existing_state is not state:
                    o = existing_state.obj()
                    if o is not None:
                        raise sa_exc.InvalidRequestError(
                            "Can't attach instance "
                            "%s; another instance with key %s is already "
                            "present in this session."
                            % (orm_util.state_str(state), state.key)
                        )
                else:
                    return False
        self._dict[key] = state
        self._manage_incoming_state(state)
        return True

    def _add_unpresent(
        self, state: InstanceState[Any], key: _IdentityKeyType[Any]
    ) -> None:
        # inlined form of add() called by loading.py
        self._dict[key] = state
        state._instance_dict = self._wr

    def fast_get_state(
        self, key: _IdentityKeyType[_O]
    ) -> Optional[InstanceState[_O]]:
        return self._dict.get(key)

    def get(
        self, key: _IdentityKeyType[_O], default: Optional[_O] = None
    ) -> Optional[_O]:
        if key not in self._dict:
            return default
        try:
            state = cast("InstanceState[_O]", self._dict[key])
        except KeyError:
            # catch gc removed the key after we just checked for it
            return default
        else:
            o = state.obj()
            if o is None:
                return default
            return o

    def items(self) -> List[Tuple[_IdentityKeyType[Any], InstanceState[Any]]]:
        values = self.all_states()
        result = []
        for state in values:
            value = state.obj()
            key = state.key
            assert key is not None
            if value is not None:
                result.append((key, value))
        return result

    def values(self) -> List[object]:
        values = self.all_states()
        result = []
        for state in values:
            value = state.obj()
            if value is not None:
                result.append(value)

        return result

    def __iter__(self) -> Iterator[_IdentityKeyType[Any]]:
        return iter(self.keys())

    def all_states(self) -> List[InstanceState[Any]]:
        return list(self._dict.values())

    def _fast_discard(self, state: InstanceState[Any]) -> None:
        # used by InstanceState for state being
        # GC'ed, inlines _managed_removed_state
        key = state.key
        assert key is not None
        try:
            st = self._dict[key]
        except KeyError:
            # catch gc removed the key after we just checked for it
            pass
        else:
            if st is state:
                self._dict.pop(key, None)

    def discard(self, state: InstanceState[Any]) -> None:
        self.safe_discard(state)

    def safe_discard(self, state: InstanceState[Any]) -> None:
        key = state.key
        if key in self._dict:
            assert key is not None
            try:
                st = self._dict[key]
            except KeyError:
                # catch gc removed the key after we just checked for it
                pass
            else:
                if st is state:
                    self._dict.pop(key, None)
                    self._manage_removed_state(state)


def _killed(state: InstanceState[Any], key: _IdentityKeyType[Any]) -> NoReturn:
    # external function to avoid creating cycles when assigned to
    # the IdentityMap
    raise sa_exc.InvalidRequestError(
        "Object %s cannot be converted to 'persistent' state, as this "
        "identity map is no longer valid.  Has the owning Session "
        "been closed?" % orm_util.state_str(state),
        code="lkrp",
    )