addon_utils.py

# SPDX-FileCopyrightText: 2011-2023 Blender Authors
#
# SPDX-License-Identifier: GPL-2.0-or-later

__all__ = (
    "paths",
    "modules",
    "check",
    "check_extension",
    "enable",
    "disable",
    "disable_all",
    "reset_all",
    "module_bl_info",
    "extensions_refresh",
    "stale_pending_remove_paths",
    "stale_pending_stage_paths",
)

import bpy as _bpy
_preferences = _bpy.context.preferences

error_encoding = False
# (name, file, path)
error_duplicates = []
addons_fake_modules = {}

# Global cached extensions, set before loading extensions on startup.
# `{addon_module_name: "Reason for incompatibility", ...}`
_extensions_incompatible = {}
# Global extension warnings, lazily calculated when displaying extensions.
# `{addon_module_name: "Warning", ...}`
_extensions_warnings = {}

# Filename used for stale files (which we can't delete).
_stale_filename = ".~stale~"


# Don't display these in the UI, unless extension development is enabled.
#
# NOTE: these add-ons will *not* be included in `bpy.context.preferences.addons`,
# therefore they cannot have saved preferences. Ideally this would be supported,
# which could be part of an improvement to store preferences for disabled add-ons.
# This is the reason we can't include "cycles".
# See #71486 and follow up discussion on #151863.
_addons_hidden_core = {
    "bl_pkg",
    "io_anim_bvh",
    "io_curve_svg",
    "io_mesh_uv_layout",
    "io_scene_fbx",
}


# Called only once at startup, avoids calling 'reset_all', correct but slower.
def _initialize_once():
    for path in paths():
        _bpy.utils._sys_path_ensure_append(path)

    _stale_pending_check_and_remove_once()

    _initialize_extensions_repos_once()

    for addon in _preferences.addons:
        if (module_name := addon.module) in _addons_hidden_core:
            continue
        enable(
            module_name,
            # Ensured by `_initialize_extensions_repos_once`.
            refresh_handled=True,
        )

    for module_name in _addons_hidden_core:
        enable(
            module_name,
            # Ensured by `_initialize_extensions_repos_once`.
            refresh_handled=True,
            default_set=False,
            persistent=True,
        )


def paths():
    import os

    paths = []
    for i, p in enumerate(_bpy.utils.script_paths()):
        # Bundled add-ons are always first.
        # Since this isn't officially part of the API, print an error so this never silently fails.
        addon_dir = os.path.join(p, "addons_core" if i == 0 else "addons")
        if os.path.isdir(addon_dir):
            paths.append(addon_dir)
        elif i == 0:
            print("Internal error:", addon_dir, "was not found!")
    return paths


# A version of `paths` that includes extension repositories returning a list `(path, package)` pairs.
#
# Notes on the ``package`` value.
#
# - For top-level modules (the "addons" directories, the value is an empty string)
#   because those add-ons can be imported directly.
# - For extension repositories the value is a module string (which can be imported for example)
#   where any modules within the `path` can be imported as a sub-module.
#   So for example, given a list value of: `("/tmp/repo", "bl_ext.temp_repo")`.
#
#   An add-on located at `/tmp/repo/my_handy_addon.py` will have a unique module path of:
#   `bl_ext.temp_repo.my_handy_addon`, which can be imported and will be the value of it's `Addon.module`.
def _paths_with_extension_repos():

    import os
    addon_paths = [(path, "") for path in paths()]
    for repo in _preferences.extensions.repos:
        if not repo.enabled:
            continue
        dirpath = repo.directory
        if not os.path.isdir(dirpath):
            continue
        addon_paths.append((dirpath, "{:s}.{:s}".format(_ext_base_pkg_idname, repo.module)))

    return addon_paths


def _fake_module(mod_name, mod_path, speedy=True):
    global error_encoding
    import os

    if _bpy.app.debug_python:
        print("fake_module", mod_path, mod_name)

    if mod_name.startswith(_ext_base_pkg_idname_with_dot):
        return _fake_module_from_extension(mod_name, mod_path)

    import ast
    ModuleType = type(ast)
    try:
        file_mod = open(mod_path, "r", encoding='UTF-8')
    except OSError as ex:
        print("Error opening file:", mod_path, ex)
        return None

    with file_mod:
        if speedy:
            lines = []
            line_iter = iter(file_mod)
            line = ""
            while not line.startswith("bl_info"):
                try:
                    line = line_iter.readline()
                except UnicodeDecodeError as ex:
                    if not error_encoding:
                        error_encoding = True
                        print("Error reading file as UTF-8:", mod_path, ex)
                    return None

                if len(line) == 0:
                    break
            while line.rstrip():
                lines.append(line)
                try:
                    line = line_iter.readline()
                except UnicodeDecodeError as ex:
                    if not error_encoding:
                        error_encoding = True
                        print("Error reading file as UTF-8:", mod_path, ex)
                    return None

            data = "".join(lines)

        else:
            data = file_mod.read()
    del file_mod

    try:
        ast_data = ast.parse(data, filename=mod_path)
    except Exception:
        print("Syntax error 'ast.parse' cannot read:", repr(mod_path))
        import traceback
        traceback.print_exc()
        ast_data = None

    body_info = None

    if ast_data:
        for body in ast_data.body:
            if body.__class__ == ast.Assign:
                if len(body.targets) == 1:
                    if getattr(body.targets[0], "id", "") == "bl_info":
                        body_info = body
                        break

    if body_info:
        try:
            mod = ModuleType(mod_name)
            mod.bl_info = ast.literal_eval(body.value)
            mod.__file__ = mod_path
            mod.__time__ = os.path.getmtime(mod_path)
        except Exception:
            print("AST error parsing bl_info for:", repr(mod_path))
            import traceback
            traceback.print_exc()
            return None

        return mod
    else:
        print("Warning: add-on missing 'bl_info', this can cause poor performance!:", repr(mod_path))
        return None


def modules_refresh(*, module_cache=addons_fake_modules):
    global error_encoding
    import os

    error_encoding = False
    error_duplicates.clear()

    modules_stale = set(module_cache.keys())

    for path, pkg_id in _paths_with_extension_repos():
        for mod_name, mod_path in _bpy.path.module_names(path, package=pkg_id):
            modules_stale.discard(mod_name)
            mod = module_cache.get(mod_name)
            if mod is not None:
                if mod.__file__ != mod_path:
                    print(
                        "multiple addons with the same name:\n"
                        "  {!r}\n"
                        "  {!r}".format(mod.__file__, mod_path)
                    )
                    error_duplicates.append((mod.bl_info["name"], mod.__file__, mod_path))

                elif (
                        (mod.__time__ != os.path.getmtime(metadata_path := mod_path)) if not pkg_id else
                        # Check the manifest time as this is the source of the cache.
                        (mod.__time_manifest__ != os.path.getmtime(metadata_path := mod.__file_manifest__))
                ):
                    print("reloading addon meta-data:", mod_name, repr(metadata_path), "(time-stamp change detected)")
                    del module_cache[mod_name]
                    mod = None

            if mod is None:
                mod = _fake_module(
                    mod_name,
                    mod_path,
                )
                if mod:
                    module_cache[mod_name] = mod

    # just in case we get stale modules, not likely
    for mod_stale in modules_stale:
        del module_cache[mod_stale]
    del modules_stale


def modules(*, module_cache=addons_fake_modules, refresh=True):
    if refresh or ((module_cache is addons_fake_modules) and modules._is_first):
        modules_refresh(module_cache=module_cache)
        modules._is_first = False

        # Dictionaries are ordered in more recent versions of Python,
        # re-create the dictionary from sorted items.
        # This avoids having to sort on every call to this function.
        module_cache_items = list(module_cache.items())
        # Sort by name with the module name as a tie breaker.
        module_cache_items.sort(key=lambda item: ((item[1].bl_info.get("name") or item[0]).casefold(), item[0]))
        module_cache.clear()
        module_cache.update((key, value) for key, value in module_cache_items)

    return module_cache.values()


modules._is_first = True


def check(module_name):
    """
    Returns the loaded state of the addon.

    :param module_name: The name of the addon and module.
    :type module_name: str
    :return: (loaded_default, loaded_state)
    :rtype: tuple[bool, bool]
    """
    import sys
    loaded_default = module_name in _preferences.addons

    mod = sys.modules.get(module_name)
    loaded_state = (
        (mod is not None) and
        getattr(mod, "__addon_enabled__", Ellipsis)
    )

    if loaded_state is Ellipsis:
        print(
            "Warning: addon-module", module_name, "found module "
            "but without '__addon_enabled__' field, "
            "possible name collision from file:",
            repr(getattr(mod, "__file__", "<unknown>")),
        )

        loaded_state = False

    if mod and getattr(mod, "__addon_persistent__", False):
        loaded_default = True

    return loaded_default, loaded_state


def check_extension(module_name):
    """
    Return true if the module is an extension.
    """
    return module_name.startswith(_ext_base_pkg_idname_with_dot)


# utility functions


def _addon_ensure(module_name):
    addons = _preferences.addons
    addon = addons.get(module_name)
    if not addon:
        addon = addons.new()
        addon.module = module_name


def _addon_remove(module_name):
    addons = _preferences.addons

    while module_name in addons:
        addon = addons.get(module_name)
        if addon:
            addons.remove(addon)


def enable(module_name, *, default_set=False, persistent=False, refresh_handled=False, handle_error=None):
    """
    Enables an addon by name.

    :param module_name: the name of the addon and module.
    :type module_name: str
    :param default_set: Set the user-preference.
    :type default_set: bool
    :param persistent: Ensure the addon is enabled for the entire session (after loading new files).
    :type persistent: bool
    :param refresh_handled: When true, :func:`extensions_refresh` must have been called with ``module_name``
       included in ``addon_modules_pending``.
       This should be used to avoid many calls to refresh extensions when enabling multiple add-ons at once.
    :type refresh_handled: bool
    :param handle_error: Called in the case of an error, taking an exception argument.
    :type handle_error: Callable[[Exception], None] | None
    :return: the loaded module or None on failure.
    :rtype: ModuleType
    """

    import os
    import sys
    import importlib
    from _bpy_restrict_state import RestrictBlend

    if handle_error is None:
        def handle_error(ex):
            if isinstance(ex, ImportError):
                # NOTE: checking "Add-on " prefix is rather weak,
                # it's just a way to avoid the noise of a full trace-back when
                # an add-on is simply missing on the file-system.
                if (type(msg := ex.msg) is str) and msg.startswith("Add-on "):
                    print(msg)
                    return
            import traceback
            traceback.print_exc()

    if (is_extension := module_name.startswith(_ext_base_pkg_idname_with_dot)):
        if not refresh_handled:
            extensions_refresh(
                addon_modules_pending=[module_name],
                handle_error=handle_error,
            )

        # Ensure the extensions are compatible.
        if _extensions_incompatible:
            if (error := _extensions_incompatible.get(
                    module_name[len(_ext_base_pkg_idname_with_dot):].partition(".")[0::2],
            )):
                try:
                    raise RuntimeError("Extension {:s} is incompatible ({:s})".format(module_name, error))
                except RuntimeError as ex:
                    handle_error(ex)
                    # No need to call `extensions_refresh` because incompatible extensions
                    # will not have their wheels installed.
                    return None

        # NOTE: from now on, before returning None, `extensions_refresh()` must be called
        # to ensure wheels setup in anticipation for this extension being used are removed upon failure.

    # reload if the mtime changes
    mod = sys.modules.get(module_name)
    # chances of the file _not_ existing are low, but it could be removed

    # Set to `mod.__file__` or None.
    mod_file = None

    if (
            (mod is not None) and
            (mod_file := mod.__file__) is not None and
            os.path.exists(mod_file)
    ):

        if getattr(mod, "__addon_enabled__", False):
            # This is an unlikely situation,
            # re-register if the module is enabled.
            # Note: the UI doesn't allow this to happen,
            # in most cases the caller should 'check()' first.
            try:
                mod.unregister()
            except Exception as ex:
                print("Exception in module unregister():", (mod_file or module_name))
                handle_error(ex)
                if is_extension and not refresh_handled:
                    extensions_refresh(handle_error=handle_error)
                return None

        mod.__addon_enabled__ = False
        mtime_orig = getattr(mod, "__time__", 0)
        mtime_new = os.path.getmtime(mod_file)
        if mtime_orig != mtime_new:
            print("module changed on disk:", repr(mod_file), "reloading...")

            try:
                importlib.reload(mod)
            except Exception as ex:
                handle_error(ex)
                del sys.modules[module_name]

                if is_extension and not refresh_handled:
                    extensions_refresh(handle_error=handle_error)
                return None
            mod.__addon_enabled__ = False

    # add the addon first it may want to initialize its own preferences.
    # must remove on fail through.
    if default_set:
        _addon_ensure(module_name)

    # Split registering up into 3 steps so we can undo
    # if it fails par way through.

    # Disable the context: using the context at all
    # while loading an addon is really bad, don't do it!
    with RestrictBlend():

        # 1) try import
        try:
            # Use instead of `__import__` so that sub-modules can eventually be supported.
            # This is also documented to be the preferred way to import modules.
            mod = importlib.import_module(module_name)
            if (mod_file := mod.__file__) is None:
                # This can happen when:
                # - The add-on has been removed but there are residual `.pyc` files left behind.
                # - An extension is a directory that doesn't contain an `__init__.py` file.
                #
                # Include a message otherwise the "cause:" for failing to load the module is left blank.
                # Include the `__path__` when available so there is a reference to the location that failed to load.
                raise ImportError(
                    "module loaded with no associated file, __path__={!r}, aborting!".format(
                        getattr(mod, "__path__", None)
                    ),
                    name=module_name,
                )
            mod.__time__ = os.path.getmtime(mod_file)
            mod.__addon_enabled__ = False
        except Exception as ex:
            # If the add-on doesn't exist, don't print full trace-back because the back-trace is in this case
            # is verbose without any useful details. A missing path is better communicated in a short message.
            # Account for `ImportError` & `ModuleNotFoundError`.
            if isinstance(ex, ImportError):
                if ex.name == module_name:
                    ex.msg = "Add-on not loaded: \"{:s}\", cause: {:s}".format(module_name, str(ex))

                # Issue with an add-on from an extension repository, report a useful message.
                elif is_extension and module_name.startswith(ex.name + "."):
                    repo_id = module_name[len(_ext_base_pkg_idname_with_dot):].rpartition(".")[0]
                    repo = next(
                        (repo for repo in _preferences.extensions.repos if repo.module == repo_id),
                        None,
                    )
                    if repo is None:
                        ex.msg = (
                            "Add-on not loaded: \"{:s}\", cause: extension repository \"{:s}\" doesn't exist".format(
                                module_name, repo_id,
                            )
                        )
                    elif not repo.enabled:
                        ex.msg = (
                            "Add-on not loaded: \"{:s}\", cause: extension repository \"{:s}\" is disabled".format(
                                module_name, repo_id,
                            )
                        )
                    else:
                        # The repository exists and is enabled, it should have imported.
                        ex.msg = "Add-on not loaded: \"{:s}\", cause: {:s}".format(module_name, str(ex))

            handle_error(ex)

            if default_set:
                _addon_remove(module_name)
            if is_extension and not refresh_handled:
                extensions_refresh(handle_error=handle_error)
            return None

        if is_extension:
            # Handle the case the an extension has `bl_info` (which is not used for extensions).
            # Note that internally a `bl_info` is added based on the extensions manifest - for compatibility.
            # So it's important not to use this one.
            bl_info = getattr(mod, "bl_info", None)
            if bl_info is not None:
                # Use `_init` to detect when `bl_info` was generated from the manifest, see: `_bl_info_from_extension`.
                if type(bl_info) is dict and "_init" not in bl_info:
                    # This print is noisy, hide behind a debug flag.
                    # Once `bl_info` is fully deprecated this should be changed to always print a warning.
                    if _bpy.app.debug_python:
                        print(
                            "Add-on \"{:s}\" has a \"bl_info\" which will be ignored in favor of \"{:s}\"".format(
                                module_name, _ext_manifest_filename_toml,
                            )
                        )
                # Always remove as this is not expected to exist and will be lazily initialized.
                del mod.bl_info

        # 2) Try register collected modules.
        # Removed register_module, addons need to handle their own registration now.

        # Core add-ons are unconditionally enabled and don't support being filtered out.
        use_owner = is_extension or (module_name not in _addons_hidden_core)

        from _bpy import _bl_owner_id_get, _bl_owner_id_set
        owner_id_prev = _bl_owner_id_get()
        _bl_owner_id_set(module_name if use_owner else "")

        # 3) Try run the modules register function.
        try:
            mod.register()
        except Exception as ex:
            print("Exception in module register():", (mod_file or module_name))
            handle_error(ex)
            del sys.modules[module_name]
            if default_set:
                _addon_remove(module_name)
            if is_extension and not refresh_handled:
                extensions_refresh(handle_error=handle_error)
            return None
        finally:
            _bl_owner_id_set(owner_id_prev)

    # * OK loaded successfully! *
    mod.__addon_enabled__ = True
    mod.__addon_persistent__ = persistent

    if _bpy.app.debug_python:
        print("\taddon_utils.enable", mod.__name__)

    return mod


def disable(module_name, *, default_set=False, refresh_handled=False, handle_error=None):
    """
    Disables an addon by name.

    :param module_name: The name of the addon and module.
    :type module_name: str
    :param default_set: Set the user-preference.
    :type default_set: bool
    :param handle_error: Called in the case of an error, taking an exception argument.
    :type handle_error: Callable[[Exception], None] | None
    """
    import sys

    if handle_error is None:
        def handle_error(_ex):
            import traceback
            traceback.print_exc()

    mod = sys.modules.get(module_name)

    # Possible this add-on is from a previous session and didn't load a
    # module this time. So even if the module is not found, still disable
    # the add-on in the user preferences.
    if mod and getattr(mod, "__addon_enabled__", False) is not False:
        mod.__addon_enabled__ = False
        mod.__addon_persistent__ = False

        try:
            mod.unregister()
        except Exception as ex:
            mod_path = getattr(mod, "__file__", module_name)
            print("Exception in module unregister():", repr(mod_path))
            del mod_path
            handle_error(ex)
    else:
        print(
            "addon_utils.disable: {:s} not {:s}".format(
                module_name,
                "loaded" if mod is None else "enabled",
            )
        )

    # could be in more than once, unlikely but better do this just in case.
    if default_set:
        _addon_remove(module_name)

    if not refresh_handled:
        extensions_refresh(handle_error=handle_error)

    if _bpy.app.debug_python:
        print("\taddon_utils.disable", module_name)


def reset_all(*, reload_scripts=False):
    """
    Sets the addon state based on the user preferences.
    """
    import sys

    # Ensures stale `addons_fake_modules` isn't used.
    modules._is_first = True
    addons_fake_modules.clear()

    # Update extensions compatibility (after reloading preferences).
    # Potentially refreshing wheels too.
    extensions_refresh()

    for path, pkg_id in _paths_with_extension_repos():
        if not pkg_id:
            _bpy.utils._sys_path_ensure_append(path)

        for mod_name, _mod_path in _bpy.path.module_names(path, package=pkg_id):
            is_enabled, is_loaded = check(mod_name)

            # first check if reload is needed before changing state.
            if reload_scripts:
                import importlib
                mod = sys.modules.get(mod_name)
                if mod:
                    importlib.reload(mod)

            if is_enabled == is_loaded:
                pass
            elif is_enabled:
                enable(mod_name, refresh_handled=True)
            elif is_loaded:
                print("\taddon_utils.reset_all unloading", mod_name)
                disable(mod_name)


def disable_all():
    import sys
    # Collect modules to disable first because dict can be modified as we disable.

    # NOTE: don't use `getattr(item[1], "__addon_enabled__", False)` because this runs on all modules,
    # including 3rd party modules unrelated to Blender.
    #
    # Some modules may have their own `__getattr__` and either:
    # - Not raise an `AttributeError` (is they should),
    #   causing `hasattr` & `getattr` to raise an exception instead of treating the attribute as missing.
    # - Generate modules dynamically, modifying `sys.modules` which is being iterated over,
    #   causing a RuntimeError: "dictionary changed size during iteration".
    #
    # Either way, running 3rd party logic here can cause undefined behavior.
    # Use direct `__dict__` access to bypass `__getattr__`, see: #111649.
    modules = sys.modules.copy()
    addon_modules = [
        item for item in modules.items()
        if type(mod_dict := getattr(item[1], "__dict__", None)) is dict
        if mod_dict.get("__addon_enabled__")
    ]
    # Check the enabled state again since it's possible the disable call
    # of one add-on disables others.
    for mod_name, mod in addon_modules:
        if getattr(mod, "__addon_enabled__", False):
            disable(mod_name, refresh_handled=True)


def _blender_manual_url_prefix():
    return "https://docs.blender.org/manual/{:s}/{:d}.{:d}".format(
        _bpy.utils.manual_language_code(),
        *_bpy.app.version[:2],
    )


def _bl_info_basis():
    return {
        "name": "",
        "author": "",
        "version": (),
        "blender": (),
        "location": "",
        "description": "",
        "doc_url": "",
        "support": 'COMMUNITY',
        "category": "",
        "warning": "",
        "show_expanded": False,
    }


def module_bl_info(mod, *, info_basis=None):
    if info_basis is None:
        info_basis = _bl_info_basis()

    addon_info = getattr(mod, "bl_info", {})

    # avoid re-initializing
    if "_init" in addon_info:
        return addon_info

    if not addon_info:
        if mod.__name__.startswith(_ext_base_pkg_idname_with_dot):
            addon_info, filepath_toml = _bl_info_from_extension(mod.__name__, mod.__file__)
            if addon_info is None:
                # Unexpected, this is a malformed extension if meta-data can't be loaded.
                print("module_bl_info: failed to extract meta-data from", filepath_toml)
                # Continue to initialize dummy data.
                addon_info = {}

        mod.bl_info = addon_info

    for key, value in info_basis.items():
        addon_info.setdefault(key, value)

    if not addon_info["name"]:
        addon_info["name"] = mod.__name__

    doc_url = addon_info["doc_url"]
    if doc_url:
        doc_url_prefix = "{BLENDER_MANUAL_URL}"
        if doc_url_prefix in doc_url:
            addon_info["doc_url"] = doc_url.replace(
                doc_url_prefix,
                _blender_manual_url_prefix(),
            )

    # Remove the maintainers email while it's not private, showing prominently
    # could cause maintainers to get direct emails instead of issue tracking systems.
    import re
    if "author" in addon_info:
        addon_info["author"] = re.sub(r"\s*<.*?>", "", addon_info["author"])

    addon_info["_init"] = None
    return addon_info


# -----------------------------------------------------------------------------
# Stale File Handling
#
# Notes:
# - On startup, a file exists that indicates cleanup is needed.
#   In the common case the file doesn't exist.
#   Otherwise module paths are scanned for files to remove.
# - Since errors resolving paths to remove could result in user data loss,
#   ensure the paths are always within the (extension/add-on/app-template) directory.
# - File locking isn't used, if multiple Blender instances start at the
#   same time and try to remove the same files, this won't cause errors.
#   Even so, remove the checking file immediately avoid unnecessary
#   file-system access overhead for other Blender instances.
#
# For more implementation details see `_bpy_internal.extensions.stale_file_manager`.
# This mainly impacts WIN32 which can't remove open file handles, see: #77837 & #125049.
#
# Use for all systems as the problem can impact any system if file removal fails
# for any reason (typically permissions or file-system error).

def _stale_pending_filepath():
    # When this file exists, stale file removal is pending.
    # Try to remove stale files next launch.
    import os
    return os.path.join(_bpy.utils.user_resource('CONFIG'), "stale-pending")


def _stale_pending_stage(debug):
    import os

    stale_pending_filepath = _stale_pending_filepath()
    dirpath = os.path.dirname(stale_pending_filepath)

    if os.path.exists(stale_pending_filepath):
        return

    try:
        os.makedirs(dirpath, exist_ok=True)
        with open(stale_pending_filepath, "wb") as _:
            pass
    except Exception as ex:
        print("Unable to set stale files pending:", str(ex))


def _stale_file_directory_iter():
    import os

    for repo in _preferences.extensions.repos:
        if not repo.enabled:
            continue
        if repo.source == 'SYSTEM':
            continue
        yield repo.directory

    # Skip `addons_core` because add-ons because these will never be uninstalled by the user.
    yield from paths()[1:]

    # The `local_dir`, for wheels.
    yield os.path.join(_bpy.utils.user_resource('EXTENSIONS'), ".local")

    # The `path_app_templates`, for user app-templates.
    yield _bpy.utils.user_resource(
        'SCRIPTS',
        path=os.path.join("startup", "bl_app_templates_user"),
        create=False,
    )


def _stale_pending_check_and_remove_once():
    # This runs on every startup, early exit if no stale data removal is staged.
    import os
    stale_pending_filepath = _stale_pending_filepath()
    if not os.path.exists(stale_pending_filepath):
        return

    # Some stale data needs to be removed, this is an exceptional case.
    # Allow for slower logic than is typically accepted on startup.
    from _bpy_internal.extensions.stale_file_manager import StaleFiles
    debug = _bpy.app.debug_python

    # Remove the pending file if all are removed.
    is_empty = True

    for dirpath in _stale_file_directory_iter():
        if not os.path.exists(os.path.join(dirpath, _stale_filename)):
            continue

        try:
            stale_handle = StaleFiles(
                base_directory=dirpath,
                stale_filename=_stale_filename,
                debug=debug,
            )
            stale_handle.state_load(check_exists=True)
            if not stale_handle.is_empty():
                stale_handle.state_remove_all()
                if not stale_handle.is_empty():
                    is_empty = False
            if stale_handle.is_modified():
                stale_handle.state_store(check_exists=False)
        except Exception as ex:
            print("Unexpected error clearing stale data, this is a bug!", str(ex))

    if is_empty:
        try:
            os.remove(stale_pending_filepath)
        except Exception as ex:
            if debug:
                print("Failed to remove stale-pending file:", str(ex))


def stale_pending_stage_paths(path_base, paths):
    # - `path_base` must a directory iterated over by `_stale_file_directory_iter`.
    #   Otherwise the stale files will never be removed.
    # - `paths` must be absolute paths which could not be removed.
    #   They must be located within `base_path` otherwise they cannot be removed.
    from _bpy_internal.extensions.stale_file_manager import StaleFiles

    debug = _bpy.app.debug_python

    stale_handle = StaleFiles(
        base_directory=path_base,
        stale_filename=_stale_filename,
        debug=debug,
    )
    # Already checked.
    if stale_handle.state_load_add_and_store(paths=paths):
        # Force clearing stale files on next restart.
        _stale_pending_stage(debug)


def stale_pending_remove_paths(path_base, paths):
    # The reverse of: `stale_pending_stage_paths`.
    from _bpy_internal.extensions.stale_file_manager import StaleFiles

    debug = _bpy.app.debug_python

    stale_handle = StaleFiles(
        base_directory=path_base,
        stale_filename=_stale_filename,
        debug=debug,
    )
    # Already checked.
    if stale_handle.state_load_remove_and_store(paths=paths):
        # Don't attempt to reverse the `_stale_pending_stage` call.
        # This is not trivial since other repositories may need to be cleared.
        # There will be a minor performance hit on restart but this is enough
        # of a corner case that it's not worth attempting to calculate if
        # removal of pending files is needed or not.
        pass


# -----------------------------------------------------------------------------
# Extension Pre-Flight Compatibility Check
#
# Check extension compatibility on startup so any extensions which are incompatible with Blender are marked as
# incompatible and wont be loaded. This cache avoids having to scan all extensions on startup on *every* startup.
#
# Implementation:
#
# The emphasis for this cache is to have minimum overhead for the common case where:
# - The simple case where there are no extensions enabled (running tests, background tasks etc).
# - The more involved case where extensions are enabled and have not changed since last time Blender started.
#   In this case do as little as possible since it runs on every startup, the following steps are unavoidable.
# - When reading compatibility cache, then run the following tests, regenerating when changes are detected.
#   - Compare with previous blender version/platform.
#   - Stat the manifests of all enabled extensions, testing that their modification-time and size are unchanged.
# - When any changes are detected,
#   regenerate compatibility information which does more expensive operations
#   (loading manifests, check version ranges etc).
#
# Other notes:
#
# - This internal format may change at any point, regenerating the cache should be reasonably fast
#   but may introduce a small but noticeable pause on startup for user configurations that contain many extensions.
# - Failure to load will simply ignore the file and regenerate the file as needed.
#
# Format:
#
# - The cache is ZLIB compressed pickled Python dictionary.
# - The dictionary keys are as follows:
#   `"blender": (bpy.app.version, platform.system(), platform.machine(), python_version, magic_number)`
#   `"filesystem": [(repo_module, pkg_id, manifest_time, manifest_size), ...]`
#   `"incompatible": {(repo_module, pkg_id): "Reason for being incompatible", ...}`
#


def _pickle_zlib_file_read(filepath):
    import pickle
    import gzip

    with gzip.GzipFile(filepath, "rb") as fh:
        data = pickle.load(fh)
    return data


def _pickle_zlib_file_write(filepath, data) -> None:
    import pickle
    import gzip

    with gzip.GzipFile(filepath, "wb", compresslevel=9) as fh:
        pickle.dump(data, fh)


def _extension_repos_module_to_directory_map():
    return {repo.module: repo.directory for repo in _preferences.extensions.repos if repo.enabled}


def _extension_compat_cache_update_needed(
        cache_data,  # `dict[str, Any]`
        blender_id,  # `tuple[Any, ...]`
        extensions_enabled,  # `set[tuple[str, str]]`
        print_debug,  # `Callable[[Any], None] | None`
):  # `-> bool`

    # Detect when Blender itself changes.
    if cache_data.get("blender") != blender_id:
        if print_debug is not None:
            print_debug("blender changed")
        return True

    # Detect when any of the extensions paths change.
    cache_filesystem = cache_data.get("filesystem", [])

    # Avoid touching the file-system if at all possible.
    # When the length is the same and all cached ID's are in this set, we can be sure they are a 1:1 patch.
    if len(cache_filesystem) != len(extensions_enabled):
        if print_debug is not None:
            print_debug("length changes ({:d} -> {:d}).".format(len(cache_filesystem), len(extensions_enabled)))
        return True

    from os import stat
    from os.path import join
    repos_module_to_directory_map = _extension_repos_module_to_directory_map()

    for repo_module, pkg_id, cache_stat_time, cache_stat_size in cache_filesystem:
        if (repo_module, pkg_id) not in extensions_enabled:
            if print_debug is not None:
                print_debug("\"{:s}.{:s}\" no longer enabled.".format(repo_module, pkg_id))
            return True

        if repo_directory := repos_module_to_directory_map.get(repo_module, ""):
            pkg_manifest_filepath = join(repo_directory, pkg_id, _ext_manifest_filename_toml)
        else:
            pkg_manifest_filepath = ""

        # It's possible an extension has been set as an add-on but cannot find the repository it came from.
        # In this case behave as if the file can't be found (because it can't) instead of ignoring it.