Source code for xonsh.lazyasd

"""Lazy and self destructive containers for speeding up module import."""
# Copyright 2015-2016, the xonsh developers. All rights reserved.
import os
import sys
import time
import types
import builtins
import threading
import importlib
import importlib.util
import collections.abc as cabc

__version__ = '0.1.3'


[docs]class LazyObject(object): def __init__(self, load, ctx, name): """Lazily loads an object via the load function the first time an attribute is accessed. Once loaded it will replace itself in the provided context (typically the globals of the call site) with the given name. For example, you can prevent the compilation of a regular expression until it is actually used:: DOT = LazyObject((lambda: re.compile('.')), globals(), 'DOT') Parameters ---------- load : function with no arguments A loader function that performs the actual object construction. ctx : Mapping Context to replace the LazyObject instance in with the object returned by load(). name : str Name in the context to give the loaded object. This *should* be the name on the LHS of the assignment. """ self._lasdo = { 'loaded': False, 'load': load, 'ctx': ctx, 'name': name, } def _lazy_obj(self): d = self._lasdo if d['loaded']: obj = d['obj'] else: obj = d['load']() d['ctx'][d['name']] = d['obj'] = obj d['loaded'] = True return obj def __getattribute__(self, name): if name == '_lasdo' or name == '_lazy_obj': return super().__getattribute__(name) obj = self._lazy_obj() return getattr(obj, name) def __bool__(self): obj = self._lazy_obj() return bool(obj) def __iter__(self): obj = self._lazy_obj() yield from obj def __getitem__(self, item): obj = self._lazy_obj() return obj[item] def __setitem__(self, key, value): obj = self._lazy_obj() obj[key] = value def __delitem__(self, item): obj = self._lazy_obj() del obj[item] def __call__(self, *args, **kwargs): obj = self._lazy_obj() return obj(*args, **kwargs) def __lt__(self, other): obj = self._lazy_obj() return obj < other def __le__(self, other): obj = self._lazy_obj() return obj <= other def __eq__(self, other): obj = self._lazy_obj() return obj == other def __ne__(self, other): obj = self._lazy_obj() return obj != other def __gt__(self, other): obj = self._lazy_obj() return obj > other def __ge__(self, other): obj = self._lazy_obj() return obj >= other def __hash__(self): obj = self._lazy_obj() return hash(obj) def __or__(self, other): obj = self._lazy_obj() return obj | other def __str__(self): return str(self._lazy_obj()) def __repr__(self): return repr(self._lazy_obj())
[docs]def lazyobject(f): """Decorator for constructing lazy objects from a function.""" return LazyObject(f, f.__globals__, f.__name__)
[docs]class LazyDict(cabc.MutableMapping): def __init__(self, loaders, ctx, name): """Dictionary like object that lazily loads its values from an initial dict of key-loader function pairs. Each key is loaded when its value is first accessed. Once fully loaded, this object will replace itself in the provided context (typically the globals of the call site) with the given name. For example, you can prevent the compilation of a bunch of regular expressions until they are actually used:: RES = LazyDict({ 'dot': lambda: re.compile('.'), 'all': lambda: re.compile('.*'), 'two': lambda: re.compile('..'), }, globals(), 'RES') Parameters ---------- loaders : Mapping of keys to functions with no arguments A mapping of loader function that performs the actual value construction upon access. ctx : Mapping Context to replace the LazyDict instance in with the the fully loaded mapping. name : str Name in the context to give the loaded mapping. This *should* be the name on the LHS of the assignment. """ self._loaders = loaders self._ctx = ctx self._name = name self._d = type(loaders)() # make sure to return the same type def _destruct(self): if len(self._loaders) == 0: self._ctx[self._name] = self._d def __getitem__(self, key): d = self._d if key in d: val = d[key] else: # pop will raise a key error for us loader = self._loaders.pop(key) d[key] = val = loader() self._destruct() return val def __setitem__(self, key, value): self._d[key] = value if key in self._loaders: del self._loaders[key] self._destruct() def __delitem__(self, key): if key in self._d: del self._d[key] else: del self._loaders[key] self._destruct() def __iter__(self): yield from (set(self._d.keys()) | set(self._loaders.keys())) def __len__(self): return len(self._d) + len(self._loaders)
[docs]def lazydict(f): """Decorator for constructing lazy dicts from a function.""" return LazyDict(f, f.__globals__, f.__name__)
[docs]class LazyBool(object): def __init__(self, load, ctx, name): """Boolean like object that lazily computes it boolean value when it is first asked. Once loaded, this result will replace itself in the provided context (typically the globals of the call site) with the given name. For example, you can prevent the complex boolean until it is actually used:: ALIVE = LazyDict(lambda: not DEAD, globals(), 'ALIVE') Parameters ---------- load : function with no arguments A loader function that performs the actual boolean evaluation. ctx : Mapping Context to replace the LazyBool instance in with the the fully loaded mapping. name : str Name in the context to give the loaded mapping. This *should* be the name on the LHS of the assignment. """ self._load = load self._ctx = ctx self._name = name self._result = None def __bool__(self): if self._result is None: res = self._ctx[self._name] = self._result = self._load() else: res = self._result return res
[docs]def lazybool(f): """Decorator for constructing lazy booleans from a function.""" return LazyBool(f, f.__globals__, f.__name__)
# # Background module loaders #
[docs]class BackgroundModuleProxy(types.ModuleType): """Proxy object for modules loaded in the background that block attribute access until the module is loaded.. """ def __init__(self, modname): self.__dct__ = { 'loaded': False, 'modname': modname, } def __getattribute__(self, name): passthrough = frozenset({'__dct__', '__class__', '__spec__'}) if name in passthrough: return super().__getattribute__(name) dct = self.__dct__ modname = dct['modname'] if dct['loaded']: mod = sys.modules[modname] else: delay_types = (BackgroundModuleProxy, type(None)) while isinstance(sys.modules.get(modname, None), delay_types): time.sleep(0.001) mod = sys.modules[modname] dct['loaded'] = True # some modules may do construction after import, give them a second stall = 0 while not hasattr(mod, name) and stall < 1000: stall += 1 time.sleep(0.001) return getattr(mod, name)
[docs]class BackgroundModuleLoader(threading.Thread): """Thread to load modules in the background.""" def __init__(self, name, package, replacements, *args, **kwargs): super().__init__(*args, **kwargs) self.daemon = True self.name = name self.package = package self.replacements = replacements self.start()
[docs] def run(self): # wait for other modules to stop being imported # We assume that module loading is finished when sys.modules doesn't # get longer in 5 consecutive 1ms waiting steps counter = 0 last = -1 while counter < 5: new = len(sys.modules) if new == last: counter += 1 else: last = new counter = 0 time.sleep(0.001) # now import module properly modname = importlib.util.resolve_name(self.name, self.package) if isinstance(sys.modules[modname], BackgroundModuleProxy): del sys.modules[modname] mod = importlib.import_module(self.name, package=self.package) for targname, varname in self.replacements.items(): if targname in sys.modules: targmod = sys.modules[targname] setattr(targmod, varname, mod)
[docs]def load_module_in_background(name, package=None, debug='DEBUG', env=None, replacements=None): """Entry point for loading modules in background thread. Parameters ---------- name : str Module name to load in background thread. package : str or None, optional Package name, has the same meaning as in importlib.import_module(). debug : str, optional Debugging symbol name to look up in the environment. env : Mapping or None, optional Environment this will default to __xonsh_env__, if available, and os.environ otherwise. replacements : Mapping or None, optional Dictionary mapping fully qualified module names (eg foo.bar.baz) that import the lazily loaded module, with the variable name in that module. For example, suppose that foo.bar imports module a as b, this dict is then {'foo.bar': 'b'}. Returns ------- module : ModuleType This is either the original module that is found in sys.modules or a proxy module that will block until delay attribute access until the module is fully loaded. """ modname = importlib.util.resolve_name(name, package) if modname in sys.modules: return sys.modules[modname] if env is None: env = getattr(builtins, '__xonsh_env__', os.environ) if env.get(debug, None): mod = importlib.import_module(name, package=package) return mod proxy = sys.modules[modname] = BackgroundModuleProxy(modname) BackgroundModuleLoader(name, package, replacements or {}) return proxy