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# Copyright 2009-2023 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
__all__ = ["lazyimport"]
import sys
import types
import threading
from portage.proxy.objectproxy import ObjectProxy
_module_proxies = {}
_module_proxies_lock = threading.RLock()
def _preload_portage_submodules():
"""
Load lazily referenced portage submodules into memory,
so imports won't fail during portage upgrade/downgrade.
Note that this recursively loads only the modules that
are lazily referenced by currently imported modules,
so some portage submodules may still remain unimported
after this function is called.
"""
imported = set()
while True:
remaining = False
for name in list(_module_proxies):
if name.startswith("portage.") or name.startswith("_emerge."):
if name in imported:
continue
imported.add(name)
remaining = True
__import__(name)
_unregister_module_proxy(name)
if not remaining:
break
def _register_module_proxy(name, proxy):
_module_proxies_lock.acquire()
try:
proxy_list = _module_proxies.get(name)
if proxy_list is None:
proxy_list = []
_module_proxies[name] = proxy_list
proxy_list.append(proxy)
finally:
_module_proxies_lock.release()
def _unregister_module_proxy(name):
"""
Destroy all proxies that reference the give module name. Also, check
for other proxies referenced by modules that have been imported and
destroy those proxies too. This way, destruction of a single proxy
can trigger destruction of all the rest. If a target module appears
to be partially imported (indicated when an AttributeError is caught),
this function will leave in place proxies that reference it.
"""
_module_proxies_lock.acquire()
try:
if name in _module_proxies:
modules = sys.modules
for name, proxy_list in list(_module_proxies.items()):
if name not in modules:
continue
# First delete this name from the dict so that
# if this same thread reenters below, it won't
# enter this path again.
del _module_proxies[name]
try:
while proxy_list:
proxy = proxy_list.pop()
object.__getattribute__(proxy, "_get_target")()
except AttributeError:
# Apparently the target module is only partially
# imported, so proxies that reference it cannot
# be destroyed yet.
proxy_list.append(proxy)
_module_proxies[name] = proxy_list
finally:
_module_proxies_lock.release()
class _LazyImport(ObjectProxy):
__slots__ = ("_scope", "_alias", "_name", "_target")
def __init__(self, scope, alias, name):
ObjectProxy.__init__(self)
object.__setattr__(self, "_scope", scope)
object.__setattr__(self, "_alias", alias)
object.__setattr__(self, "_name", name)
_register_module_proxy(name, self)
def _get_target(self):
try:
return object.__getattribute__(self, "_target")
except AttributeError:
pass
name = object.__getattribute__(self, "_name")
__import__(name)
target = sys.modules[name]
object.__setattr__(self, "_target", target)
object.__getattribute__(self, "_scope")[
object.__getattribute__(self, "_alias")
] = target
_unregister_module_proxy(name)
return target
class _LazyImportFrom(_LazyImport):
__slots__ = ("_attr_name",)
def __init__(self, scope, name, attr_name, alias):
object.__setattr__(self, "_attr_name", attr_name)
_LazyImport.__init__(self, scope, alias, name)
def _get_target(self):
try:
return object.__getattribute__(self, "_target")
except AttributeError:
pass
name = object.__getattribute__(self, "_name")
attr_name = object.__getattribute__(self, "_attr_name")
__import__(name)
try:
target = getattr(sys.modules[name], attr_name)
except AttributeError:
# Try to import it as a submodule
try:
__import__(f"{name}.{attr_name}")
except ImportError:
pass
# If it's a submodule, this will succeed. Otherwise, it may
# be that the module is only partially imported, so raise
# AttributeError for _unregister_module_proxy() to handle.
target = getattr(sys.modules[name], attr_name)
object.__setattr__(self, "_target", target)
object.__getattribute__(self, "_scope")[
object.__getattribute__(self, "_alias")
] = target
_unregister_module_proxy(name)
return target
def lazyimport(scope, *args):
"""
Create a proxy in the given scope in order to performa a lazy import.
Syntax Result
foo import foo
foo:bar,baz from foo import bar, baz
foo:bar@baz from foo import bar as baz
@param scope: the scope in which to place the import, typically globals()
@type myfilename: dict
@param args: module names to import
@type args: strings
"""
modules = sys.modules
for s in args:
parts = s.split(":", 1)
if len(parts) == 1:
name = s
if not name or not isinstance(name, str):
raise ValueError(name)
components = name.split(".")
parent_scope = scope
for i in range(len(components)):
alias = components[i]
if i < len(components) - 1:
parent_name = ".".join(components[: i + 1])
__import__(parent_name)
mod = modules.get(parent_name)
if not isinstance(mod, types.ModuleType):
# raise an exception
__import__(name)
parent_scope[alias] = mod
parent_scope = mod.__dict__
continue
already_imported = modules.get(name)
if already_imported is not None:
parent_scope[alias] = already_imported
else:
parent_scope[alias] = _LazyImport(parent_scope, alias, name)
else:
name, fromlist = parts
already_imported = modules.get(name)
fromlist = fromlist.split(",")
for s in fromlist:
if not s:
# This happens if there's an extra comma in fromlist.
raise ValueError("Empty module attribute name")
alias = s.split("@", 1)
if len(alias) == 1:
alias = alias[0]
attr_name = alias
else:
attr_name, alias = alias
if already_imported is not None:
try:
scope[alias] = getattr(already_imported, attr_name)
except AttributeError:
# Apparently the target module is only partially
# imported, so create a proxy.
already_imported = None
scope[alias] = _LazyImportFrom(scope, name, attr_name, alias)
else:
scope[alias] = _LazyImportFrom(scope, name, attr_name, alias)
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