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# Source code for astropy.config.paths

    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    """This module contains functions to determine where configuration and
    data/cache files used by Astropy should be placed.
    """

    import os
    import re
    import shutil
    import sys
    from collections.abc import Callable, Generator
    from contextlib import contextmanager, nullcontext
    from copy import deepcopy
    from dataclasses import KW_ONLY, dataclass, field, replace
    from enum import Enum, auto
    from functools import wraps
    from inspect import cleandoc
    from pathlib import Path
    from threading import RLock
    from types import TracebackType
    from typing import (
        NewType,
        ParamSpec,
        Protocol,
        TypedDict,
        assert_never,
        final,
    )
    from warnings import warn

    from astropy.config._tempfile_shim import TemporaryDirectory
    from astropy.utils.exceptions import AstropyUserWarning

    __all__ = [
        "get_cache_dir",
        "get_cache_dir_path",
        "get_config_dir",
        "get_config_dir_path",
        "set_temp_cache",
        "set_temp_config",
        "temporary_cache_dir_path",
        "temporary_config_dir_path",
    ]

    P = ParamSpec("P")

    class PathGetter(Protocol):
        def __call__(self, p: str, /, *, ensure_exists: bool = False) -> Path: ...

    class _DirType(Enum):
        CACHE = auto()
        CONFIG = auto()

        @property
        def path_getter(self) -> PathGetter:
            match self:
                case _DirType.CACHE:
                    return get_cache_dir_path
                case _DirType.CONFIG:
                    return get_config_dir_path
                case _ as unreachable:
                    assert_never(unreachable)

        @property
        def legacy_context_manager(self) -> "type[_SetTempPath]":
            match self:
                case _DirType.CACHE:
                    return set_temp_cache
                case _DirType.CONFIG:
                    return set_temp_config
                case _ as unreachable:
                    assert_never(unreachable)

        def as_str(self) -> str:
            return self.name.lower()

    @final
    @dataclass(slots=True, frozen=True, kw_only=True)
    class _Namespace:
        root: str
        fragments: tuple[str, ...] = ()

        def __post_init__(self) -> None:
            if not all(re.fullmatch(r"[\w-]+", e) for e in self.elements):
                raise ValueError("Found invalid namespace elements.")

        @classmethod
        def from_str(cls, s: str, /) -> "_Namespace":
            elements = s.split(".")
            return _Namespace(root=elements[0], fragments=tuple(elements[1:]))

        @property
        def elements(self) -> list[str]:
            return [self.root, *self.fragments]

        def join(self) -> str:
            # should round-trip with from_str
            return ".".join(self.elements)

    @final
    @dataclass(slots=True, frozen=True, kw_only=True)
    class _DirectoryElements:
        base_node: Path | None = None
        sub_nodes: list[str] = field(default_factory=list)

        def join(self) -> Path:
            if self.base_node is None:
                raise AssertionError
            return self.base_node.joinpath(*self.sub_nodes)

    Error = NewType("Error", str)

    def _resolve(var: str) -> Path | Error:
        # if a Path is returned, it is guaranteed to:
        # - exist
        # - be absolute (in conformance with the XDG standard)
        if (s := os.getenv(var)) is None:
            raise AssertionError

        msg = f"{var} is set to {s}, {{reason}}. This environment variable will be ignored."

        if not (p := Path(s)).exists():
            return Error(msg.format(reason="but no such file or directory was found"))

        if p.is_file():
            return Error(msg.format(reason="which is a file (expected a directory)"))

        if not p.is_dir():
            return Error(
                msg.format(reason="which is neither a regular file nor a directory")
            )

        if not p.is_absolute():
            return Error(msg.format(reason="which is relative (expected an absolute path)"))

        return p

    class _SpecSource(Enum):
        XDG = auto()
        ASTROPY = auto()

    @final
    @dataclass(slots=True, frozen=True, kw_only=True)
    class _Envvar:
        spec: _SpecSource
        dirtype: _DirType

        @property
        def name(self) -> str:
            match self.spec, self.dirtype:
                case _SpecSource.ASTROPY, _DirType.CACHE:
                    return "ASTROPY_CACHE_DIR"
                case _SpecSource.ASTROPY, _DirType.CONFIG:
                    return "ASTROPY_CONFIG_DIR"
                case _SpecSource.XDG, _DirType.CACHE:
                    return "XDG_CACHE_HOME"
                case _SpecSource.XDG, _DirType.CONFIG:
                    return "XDG_CONFIG_HOME"
                case _ as unreachable:
                    assert_never(unreachable)

        @property
        def value(self) -> str | None:
            return os.getenv(self.name)

        def is_defined(self) -> bool:
            return self.value not in {None, ""}

        def resolve(self) -> Path | Error:
            assert self.is_defined()
            return _resolve(self.name)

    @final
    @dataclass(slots=True, frozen=True, kw_only=True)
    class _DirectoryEnvvarSet:
        astropy: _Envvar
        xdg: _Envvar

        def __post_init__(self):
            match self.astropy.spec, self.xdg.spec:
                case _SpecSource.ASTROPY, _SpecSource.XDG:
                    pass
                case _:
                    raise AssertionError

    @final
    @dataclass(slots=True, frozen=True)
    class _DirectoryFinder:
        dirtype: _DirType
        _: KW_ONLY
        # in Python 3.15+, this should be a frozendict
        # (i.e., don't rely on this attribute's being mutable)
        overrides: dict[_Namespace, Path] = field(default_factory=dict)

        @property
        def envvars(self) -> _DirectoryEnvvarSet:
            return _DirectoryEnvvarSet(
                astropy=_Envvar(spec=_SpecSource.ASTROPY, dirtype=self.dirtype),
                xdg=_Envvar(spec=_SpecSource.XDG, dirtype=self.dirtype),
            )

        def legacy_default_base_node(self, namespace: str) -> Path:
            return Path.home() / f".{namespace}" / self.dirtype.as_str()

        def default_base_node(self) -> Path:
            # default to a XDG-compliant scheme
            return Path.home() / f".{self.dirtype.as_str()}"

        def find_directory_elements(self, namespace: str) -> _DirectoryElements:
            ns = _Namespace.from_str(namespace)
            de = _DirectoryElements(sub_nodes=ns.elements)

            if ns in self.overrides:
                return replace(de, base_node=self.overrides[ns])

            if self.envvars.astropy.is_defined() and ns.root == "astropy":
                match self.envvars.astropy.resolve():
                    case Path() as base_node:
                        return replace(de, base_node=base_node, sub_nodes=ns.fragments)
                    case str() as err:
                        warn(err, AstropyUserWarning, stacklevel=2)
                    case _ as unreachable:
                        assert_never(unreachable)

            if self.envvars.xdg.is_defined():
                match self.envvars.xdg.resolve():
                    case Path() as base_node:
                        return replace(de, base_node=base_node)
                    case str() as err:
                        warn(err, AstropyUserWarning, stacklevel=2)
                    case _ as unreachable:
                        assert_never(unreachable)

            # Default resolution. For backward compatibility, honor a legacy
            # ~/.<root>/<dirtype> directory if it exists and the new default
            # location does not. This deliberately lives in the default branch so
            # it cannot shadow an explicit override or environment variable.
            default_de = replace(de, base_node=self.default_base_node())
            legacy_node = self.legacy_default_base_node(namespace)
            if legacy_node.is_dir() and not default_de.join().exists():
                return _DirectoryElements(base_node=legacy_node)
            return default_de

        def find_namespaced_node(self, namespace: str) -> Path:
            # we intentionally let through some possibly invalid state,
            # like a file occupying the node where we expect a directory.
            # The core reason is that there'll always be a difference between the
            # time we look up the location and the time we actually use it, so it's
            # impossible to make the look up perfectly safe. In turn, the
            # responsibility to raise an exception falls on the function that'll
            # actually try to use it.
            return self.find_directory_elements(namespace).join()

    class _TempDirKwargs(TypedDict):
        dir: os.PathLike[str] | str | None
        suffix: str | None
        prefix: str | None
        delete: bool

    @contextmanager
    def _temporary_dir_ctx(
        *,
        dirtype: _DirType,
        ctx_gen,
        namespace: str,
        dir_: os.PathLike[str] | str | None = None,
        suffix: str | None = None,
        prefix: str | None = None,
        delete: bool = True,
    ) -> Generator[Path, None, None]:
        # the common implementation for temporary_cache_dir_path and temporary_config_dir_path

        kwargs: _TempDirKwargs = {
            "dir": dir_,
            "suffix": suffix,
            "prefix": prefix,
            "delete": delete,
        }
        with _finders.lock, TemporaryDirectory(**kwargs) as tmp_dir, ctx_gen():
            tmp_path = Path(tmp_dir)
            initial_df: _DirectoryFinder = _finders.get(dirtype)
            df: _DirectoryFinder = replace(
                initial_df,
                overrides=initial_df.overrides | {_Namespace.from_str(namespace): tmp_path},
            )
            _finders.set(dirtype, df)

            try:
                yield_val = df.find_namespaced_node(namespace)
                if yield_val != tmp_path:
                    assert yield_val.is_relative_to(tmp_path)
                    yield_val.mkdir(parents=True)
                yield yield_val
            finally:
                _finders.set(dirtype, initial_df)

    @contextmanager
    def _clear_cfgobjs():
        from .configuration import _cfgobjs

        with _finders.lock:
            initial_cfgobjs = deepcopy(_cfgobjs)
            _cfgobjs.clear()

            try:
                yield
            finally:
                _cfgobjs.clear()
                _cfgobjs.update(initial_cfgobjs)

    @dataclass(slots=True, kw_only=True)
    class _Finders:
        # tie in all global, mutable state from
        # this module into a single object
        cache: _DirectoryFinder
        config: _DirectoryFinder

        # Any number of threads may call any combination of set_temp_cache and set_temp_config,
        # in any order. Hence they need to share a single lock (otherwise deadlocks would be possible).
        # In particular, the possibility of nesting more than one instance of each context imposes
        # the use of a re-entrant lock (RLock).
        lock: RLock

        def get(self, dirtype: _DirType) -> _DirectoryFinder:
            match dirtype:
                case _DirType.CACHE:
                    return self.cache
                case _DirType.CONFIG:
                    return self.config
                case _ as unreachable:
                    assert_never(unreachable)

        def set(self, dirtype: _DirType, df: _DirectoryFinder) -> None:
            match dirtype:
                case _DirType.CACHE:
                    self.cache = df
                case _DirType.CONFIG:
                    self.config = df
                case _ as unreachable:
                    assert_never(unreachable)

    _finders = _Finders(
        cache=_DirectoryFinder(_DirType.CACHE),
        config=_DirectoryFinder(_DirType.CONFIG),
        lock=RLock(),
    )

    @contextmanager
    def temporary_cache_dir_path(
        dir_: os.PathLike[str] | str | None = None,
        /,
        *,
        namespace: str,
        suffix: str | None = None,
        prefix: str | None = None,
        delete: bool = True,
    ) -> Generator[Path, None, None]:
        """
        A context manager to create a temporary directory and define it as the cache
        directory associated with some namespace.

        The directory returned will shadow both ASTROPY_CACHE_DIR and XDG_CACHE_HOME
        environment variable if defined.

        This may also be used as a decorator on a function to set the cache path
        just within that function.

        Thread safety is guaranteed, but concurrency isn't:
        only a single thread at a time may execute code within this context.

        All arguments from :py:class:`tempfile.TemporaryDirectory` are optionally supported,
        with a couple differences:

        - ``dir`` is positional-only and must come first
        - all other arguments are keyword-only
        - ``delete`` is supported even on Python 3.11

        .. versionadded:: 8.0

        Parameters
        ----------
        namespace : str, keyword-only
            A mandatory unique identifier for the namespace associated to a temporary directory,
            which will used to name the directory itself.
            This string must be non-empty, and can only contain alphanumeric characters,
            ``_``, ``-`` or ``.``.
            ``.`` is special cased to represent a path separator (see ``os.sep``) in the
            output directory.

        See Also
        --------
        temporary_config_dir_path: a similar function for configuration directories
        set_temp_cache: a legacy function with similar goals but a much less predictable behavior
        """
        with _temporary_dir_ctx(
            namespace=namespace,
            dir_=dir_,
            suffix=suffix,
            prefix=prefix,
            delete=delete,
            dirtype=_DirType.CACHE,
            ctx_gen=nullcontext,
        ) as tmp_path:
            yield tmp_path

    @contextmanager
    def temporary_config_dir_path(
        dir_: os.PathLike[str] | str | None = None,
        /,
        *,
        namespace: str,
        suffix: str | None = None,
        prefix: str | None = None,
        delete: bool = True,
    ) -> Generator[Path, None, None]:
        """
        A context manager to create a temporary directory and define it as the configuration
        directory associated with some namespace.

        The directory returned will shadow both ASTROPY_CONFIG_DIR and XDG_CONFIG_HOME
        environment variable if defined.

        This may also be used as a decorator on a function to set the config path
        just within that function.

        Thread safety is guaranteed, but concurrency isn't:
        only a single thread at a time may execute code within this context.

        All arguments from :py:class:`tempfile.TemporaryDirectory` are optionally supported,
        with a couple differences:

        - ``dir`` is positional-only and must come first
        - all other arguments are keyword-only
        - ``delete`` is supported even on Python 3.11

        .. versionadded:: 8.0

        Parameters
        ----------
        namespace: str, keyword-only
            A mandatory unique identifier for the namespace associated to a temporary directory,
            which will used to name the directory itself.
            This string must be non-empty, and can only contain alphanumeric characters,
            ``_``, ``-`` or ``.``.
            ``.`` is special cased to represent a path separator (see ``os.sep``) in the
            output directory.

        See Also
        --------
        temporary_cache_dir_path: a similar function for cache directories
        set_temp_config: a legacy function with similar goals but a much less predictable behavior
        """
        with _temporary_dir_ctx(
            namespace=namespace,
            dir_=dir_,
            suffix=suffix,
            prefix=prefix,
            delete=delete,
            dirtype=_DirType.CONFIG,
            ctx_gen=_clear_cfgobjs,
        ) as tmp_path:
            yield tmp_path

    def get_config_dir_path(
        rootname: str = "astropy",
        *,
        ensure_exists: bool = True,
    ) -> Path:
        node = _finders.config.find_namespaced_node(rootname)
        if ensure_exists:
            node.mkdir(parents=True, exist_ok=True)
        return node

    def get_config_dir(
        rootname: str = "astropy",
        *,
        ensure_exists: bool = True,
    ) -> str:
        return str(get_config_dir_path(rootname, ensure_exists=ensure_exists))

    def get_cache_dir_path(
        rootname: str = "astropy",
        *,
        ensure_exists: bool = True,
    ) -> Path:
        node = _finders.cache.find_namespaced_node(rootname)
        if ensure_exists:
            node.mkdir(parents=True, exist_ok=True)
        return node

    def get_cache_dir(
        rootname: str = "astropy",
        *,
        ensure_exists: bool = True,
    ) -> str:
        return str(get_cache_dir_path(rootname, ensure_exists=ensure_exists))

    if sys.flags.optimize < 2:
        # with PYTHONOPTIMIZE=2, docstrings are stripped from everywhere,
        # so don't add them dynamically in that case

        _base_get_config_doc = """\
            Determines the configuration directory associated with a namespace and creates the
            directory if it doesn't exist.

            This directory is typically ``$XDG_CONFIG_HOME/<namespace>``, but can be overwritten
            with the ``ASTROPY_CONFIG_DIR`` environment variable, or with
            ``temporary_config_dir_path``.
            {post_header}
            .. versionchanged:: 8.0
                In previous versions, the return value pointed to ``$HOME/.astropy/config`` by default.
                A new environment variable ``ASTROPY_CONFIG_DIR`` is now supported.
                Symlinks are no longer created in any situation.

            Parameters
            ----------
            rootname : str, optional
                Namespace associated with the directory. For example, for ``'pkgname'``,
                the directory would be ``$XDG_CONFIG_HOME/pkgname``. Default: ``'astropy'``

            ensure_exists : bool, keyword-only, optional
                Whether to create the directory (and its parents) if it's missing.
                Default: True

                .. versionadded:: 8.0
            """
        _base_get_cache_doc = """\
            Determines the cache directory associated with a namespace and, optionally,
            creates the directory if it doesn't exist.

            This directory is typically ``$XDG_CACHE_HOME/<namespace>``, but can be overwritten
            with the ``ASTROPY_CACHE_DIR`` environment variable, or with
            :func:`temporary_cache_dir_path`.
            {post_header}
            .. versionchanged:: 8.0
                In previous versions, the return value pointed to ``$HOME/.astropy/cache`` by default.
                A new environment variable ``ASTROPY_CACHE_DIR`` is now supported.
                Symlinks are no longer created in any situation.

            Parameters
            ----------
            rootname : str, optional
                Namespace associated with the directory. For example, for ``'pkgname'``,
                the directory would be ``$XDG_CACHE_HOME/pkgname``. Default: ``'astropy'``

            ensure_exists : bool, keyword-only, optional
                Whether to create the directory (and its parents) if it's missing.
                Default: True

                .. versionadded:: 8.0
            """
        _ret_section = """
            Returns
            -------
            {rettype}
                The absolute path to the {dirtype} directory.
            """

        get_config_dir_path.__doc__ = cleandoc(
            _base_get_config_doc.format(post_header="\n        .. versionadded:: 7.0\n")
            + _ret_section.format(rettype="Path", dirtype="cache")
        )

        get_config_dir.__doc__ = cleandoc(
            _base_get_config_doc.format(post_header="")
            + _ret_section.format(rettype="str", dirtype="cache")
            + """
            See Also
            --------
            get_config_dir_path : same as this function, except that the return value is a pathlib.Path
            """
        )

        get_cache_dir_path.__doc__ = cleandoc(
            _base_get_cache_doc.format(post_header="\n        .. versionadded:: 7.0\n")
            + _ret_section.format(rettype="Path", dirtype="cache")
        )

        get_cache_dir.__doc__ = cleandoc(
            _base_get_cache_doc.format(post_header="")
            + _ret_section.format(rettype="str", dirtype="cache")
            + """
            See Also
            --------
            get_cache_dir_path : same as this function, except that the return value is a pathlib.Path
            """
        )

    class _SetTempPath:
        # This base class serves as a deduplication layer for its only two intended
        # children (set_temp_cache and set_temp_config)
        _dirtype: _DirType

        def __init__(
            self, path: os.PathLike[str] | str | None = None, delete: bool = False
        ) -> None:
            if path is None:
                self._path = None
            else:
                if (path := Path(path)).is_file():
                    raise FileExistsError(
                        f"{path} is a file and cannot be used as a directory"
                    )
                self._path = path.resolve()

            self._delete = delete

        @classmethod
        def _get_directory_finder(cls) -> _DirectoryFinder:
            match cls._dirtype:
                case _DirType.CACHE:
                    return _finders.cache
                case _DirType.CONFIG:
                    return _finders.config
                case _ as unreachable:
                    assert_never(unreachable)

        @classmethod
        def _get_current_override(cls) -> Path | None:
            return cls._get_directory_finder().overrides.get(_Namespace(root="astropy"))

        def __enter__(self) -> str:
            _finders.lock.acquire()
            self._prev_path = self._get_current_override()
            try:
                initial_df = self._get_directory_finder()
                self._prev_df = initial_df
                ns = _Namespace(root="astropy")
                if self._path is None:
                    overrides = initial_df.overrides.copy()
                    if ns in overrides:
                        del overrides[ns]
                else:
                    overrides = initial_df.overrides | {ns: self._path}

                df: _DirectoryFinder = replace(initial_df, overrides=overrides)
            except Exception:
                _finders.lock.release()
                raise
            try:
                _finders.set(self._dirtype, df)
                return str(df.find_namespaced_node("astropy"))
            except Exception:
                _finders.set(self._dirtype, initial_df)
                _finders.lock.release()
                raise

        def __exit__(
            self,
            type: type[BaseException] | None,
            value: BaseException | None,
            tb: TracebackType | None,
        ) -> None:
            try:
                if self._delete and self._path is not None:
                    shutil.rmtree(self._path)
            finally:
                _finders.set(self._dirtype, self._prev_df)
                _finders.lock.release()

        def __call__(self, func: Callable[P, object]) -> Callable[P, None]:
            """Implements use as a decorator."""

            @wraps(func)
            def wrapper(*args: P.args, **kwargs: P.kwargs) -> None:
                with self:
                    func(*args, **kwargs)

            return wrapper

    class set_temp_config(_SetTempPath):
        """
        Context manager to set a temporary path for the Astropy config, primarily
        for use with testing.

        If the path set by this context manager does not already exist it will be
        created, if possible.

        This may also be used as a decorator on a function to set the config path
        just within that function.

        Thread safety is guaranteed since astropy 7.2.1, but concurrency isn't:
        only a single thread at a time may execute code within this context.

        .. versionchanged:: 8.0
            This function is soft-deprecated. It won't emit deprecation warnings but its
            use is discouraged for new code, as the exact behavior is hard to predict.
            Prefer :func:`temporary_config_dir_path` where available.

        Parameters
        ----------
        path : str, optional
            The directory (which must exist) in which to find the Astropy config
            files, or create them if they do not already exist.  If None, this
            restores the config path to the user's default config path as returned
            by `get_config_dir` as though this context manager were not in effect
            (this is useful for testing).  In this case the ``delete`` argument is
            always ignored.

        delete : bool, optional
            If True, cleans up the temporary directory after exiting the temp
            context (default: False).

        See Also
        --------
        temporary_config_dir_path: a function with similar goals but a much more predictable behavior
        """

        _dirtype = _DirType.CONFIG

        def __enter__(self) -> str:
            # Special case for the config case, where we need to reset all the
            # cached config objects.  We do keep the cache, since some of it
            # may have been set programmatically rather than be stored in the
            # config file (e.g., iers.conf.auto_download=False for our tests).
            from .configuration import _cfgobjs

            _finders.lock.acquire()

            try:
                _cfgobjs_copy = _cfgobjs.copy()
            except Exception:
                _finders.lock.release()
                raise

            self._cfgobjs_copy = _cfgobjs_copy

            try:
                _cfgobjs.clear()
                return super().__enter__()
            except Exception:
                _cfgobjs.update(self._cfgobjs_copy)
                del self._cfgobjs_copy
                _finders.lock.release()
                raise

        def __exit__(
            self,
            type: type[BaseException] | None,
            value: BaseException | None,
            tb: TracebackType | None,
        ) -> None:
            try:
                from .configuration import _cfgobjs

                _cfgobjs.clear()
                _cfgobjs.update(self._cfgobjs_copy)
                del self._cfgobjs_copy
                super().__exit__(type, value, tb)
            finally:
                _finders.lock.release()

    class set_temp_cache(_SetTempPath):
        """
        Context manager to set a temporary path for the Astropy download cache,
        primarily for use with testing (though there may be other applications
        for setting a different cache directory, for example to switch to a cache
        dedicated to large files).

        If the path set by this context manager does not already exist it will be
        created, if possible.

        This may also be used as a decorator on a function to set the cache path
        just within that function.

        Thread safety is guaranteed since astropy 7.2.1, but concurrency isn't:
        only a single thread at a time may execute code within this context.

        .. versionchanged:: 8.0
            This function is soft-deprecated. It won't emit deprecation warnings but its
            use is discouraged for new code, as the exact behavior is hard to predict.
            Prefer :func:`temporary_cache_dir_path` where available.

        Parameters
        ----------
        path : str
            The directory (which must exist) in which to find the Astropy cache
            files, or create them if they do not already exist.  If None, this
            restores the cache path to the user's default cache path as returned
            by `get_cache_dir` as though this context manager were not in effect
            (this is useful for testing).  In this case the ``delete`` argument is
            always ignored.

        delete : bool, optional
            If True, cleans up the temporary directory after exiting the temp
            context (default: False).

        See Also
        --------
        temporary_cache_dir_path: a function with similar goals but a much more predictable behavior
        """

        _dirtype = _DirType.CACHE