Mercurial > hg
view hgdemandimport/demandimportpy3.py @ 35998:dce43aaaf209
lfs: allow a pointer to be extracted from a context that removes the file
This is needed to let 'set:lfs()' and '{lfs_files}' work normally on removed
files.
Yuya suggested returning a null pointer for removed files, instead of the
pointer from the parent. The first attempt at this was to return None for a non
LFS file, and a (pointer, ctx) tuple to hold the pointer and context (or parent
pointer and context for a removed file). But this complicated the callers, even
the ones that didn't care about removed files.
Instead, let's use {} to represent a removed pointer. This has the added
convenience of being a useful representation in the template language, and only
affects the callers that care about removed files (and only slightly). Since
pointers are explicitly serialized with a call to a member function, there is no
danger of writing these to disk.
author | Matt Harbison <matt_harbison@yahoo.com> |
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date | Sat, 27 Jan 2018 18:56:24 -0500 |
parents | fcb1ecf2bef7 |
children | 670eb4fa1b86 |
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# demandimportpy3 - global demand-loading of modules for Mercurial # # Copyright 2017 Facebook Inc. # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """Lazy loading for Python 3.6 and above. This uses the new importlib finder/loader functionality available in Python 3.5 and up. The code reuses most of the mechanics implemented inside importlib.util, but with a few additions: * Allow excluding certain modules from lazy imports. * Expose an interface that's substantially the same as demandimport for Python 2. This also has some limitations compared to the Python 2 implementation: * Much of the logic is per-package, not per-module, so any packages loaded before demandimport is enabled will not be lazily imported in the future. In practice, we only expect builtins to be loaded before demandimport is enabled. """ # This line is unnecessary, but it satisfies test-check-py3-compat.t. from __future__ import absolute_import import contextlib import importlib.abc import importlib.machinery import importlib.util import sys _deactivated = False class _lazyloaderex(importlib.util.LazyLoader): """This is a LazyLoader except it also follows the _deactivated global and the ignore list. """ def exec_module(self, module): """Make the module load lazily.""" if _deactivated or module.__name__ in ignore: self.loader.exec_module(module) else: super().exec_module(module) # This is 3.6+ because with Python 3.5 it isn't possible to lazily load # extensions. See the discussion in https://bugs.python.org/issue26186 for more. _extensions_loader = _lazyloaderex.factory( importlib.machinery.ExtensionFileLoader) _bytecode_loader = _lazyloaderex.factory( importlib.machinery.SourcelessFileLoader) _source_loader = _lazyloaderex.factory(importlib.machinery.SourceFileLoader) def _makefinder(path): return importlib.machinery.FileFinder( path, # This is the order in which loaders are passed in in core Python. (_extensions_loader, importlib.machinery.EXTENSION_SUFFIXES), (_source_loader, importlib.machinery.SOURCE_SUFFIXES), (_bytecode_loader, importlib.machinery.BYTECODE_SUFFIXES), ) ignore = [] def init(ignorelist): global ignore ignore = ignorelist def isenabled(): return _makefinder in sys.path_hooks and not _deactivated def disable(): try: while True: sys.path_hooks.remove(_makefinder) except ValueError: pass def enable(): sys.path_hooks.insert(0, _makefinder) @contextlib.contextmanager def deactivated(): # This implementation is a bit different from Python 2's. Python 3 # maintains a per-package finder cache in sys.path_importer_cache (see # PEP 302). This means that we can't just call disable + enable. # If we do that, in situations like: # # demandimport.enable() # ... # from foo.bar import mod1 # with demandimport.deactivated(): # from foo.bar import mod2 # # mod2 will be imported lazily. (The converse also holds -- whatever finder # first gets cached will be used.) # # Instead, have a global flag the LazyLoader can use. global _deactivated demandenabled = isenabled() if demandenabled: _deactivated = True try: yield finally: if demandenabled: _deactivated = False