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# __init__.py - Startup and module loading logic for Mercurial.
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#
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# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import imp
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import os
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import sys
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import zipimport
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from . import (
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policy
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)
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__all__ = []
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modulepolicy = policy.policy
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# Modules that have both Python and C implementations. See also the
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# set of .py files under mercurial/pure/.
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_dualmodules = set([
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'mercurial.base85',
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'mercurial.bdiff',
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'mercurial.diffhelpers',
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'mercurial.mpatch',
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'mercurial.osutil',
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'mercurial.parsers',
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])
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class hgimporter(object):
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"""Object that conforms to import hook interface defined in PEP-302."""
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def find_module(self, name, path=None):
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# We only care about modules that have both C and pure implementations.
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if name in _dualmodules:
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return self
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return None
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def load_module(self, name):
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mod = sys.modules.get(name, None)
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if mod:
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return mod
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mercurial = sys.modules['mercurial']
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# The zip importer behaves sufficiently differently from the default
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# importer to warrant its own code path.
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loader = getattr(mercurial, '__loader__', None)
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if isinstance(loader, zipimport.zipimporter):
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def ziploader(*paths):
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"""Obtain a zipimporter for a directory under the main zip."""
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path = os.path.join(loader.archive, *paths)
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zl = sys.path_importer_cache.get(path)
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if not zl:
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zl = zipimport.zipimporter(path)
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return zl
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try:
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if modulepolicy in policy.policynoc:
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raise ImportError()
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zl = ziploader('mercurial')
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mod = zl.load_module(name)
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# Unlike imp, ziploader doesn't expose module metadata that
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# indicates the type of module. So just assume what we found
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# is OK (even though it could be a pure Python module).
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except ImportError:
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if modulepolicy == 'c':
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raise
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zl = ziploader('mercurial', 'pure')
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mod = zl.load_module(name)
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sys.modules[name] = mod
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return mod
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# Unlike the default importer which searches special locations and
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# sys.path, we only look in the directory where "mercurial" was
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# imported from.
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# imp.find_module doesn't support submodules (modules with ".").
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# Instead you have to pass the parent package's __path__ attribute
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# as the path argument.
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stem = name.split('.')[-1]
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try:
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if modulepolicy in policy.policynoc:
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raise ImportError()
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modinfo = imp.find_module(stem, mercurial.__path__)
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# The Mercurial installer used to copy files from
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# mercurial/pure/*.py to mercurial/*.py. Therefore, it's possible
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# for some installations to have .py files under mercurial/*.
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# Loading Python modules when we expected C versions could result
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# in a) poor performance b) loading a version from a previous
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# Mercurial version, potentially leading to incompatibility. Either
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# scenario is bad. So we verify that modules loaded from
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# mercurial/* are C extensions. If the current policy allows the
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# loading of .py modules, the module will be re-imported from
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# mercurial/pure/* below.
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if modinfo[2][2] != imp.C_EXTENSION:
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raise ImportError('.py version of %s found where C '
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'version should exist' % name)
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except ImportError:
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if modulepolicy == 'c':
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raise
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# Could not load the C extension and pure Python is allowed. So
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# try to load them.
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from . import pure
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modinfo = imp.find_module(stem, pure.__path__)
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if not modinfo:
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raise ImportError('could not find mercurial module %s' %
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name)
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mod = imp.load_module(name, *modinfo)
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sys.modules[name] = mod
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return mod
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# Python 3 uses a custom module loader that transforms source code between
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# source file reading and compilation. This is done by registering a custom
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# finder that changes the spec for Mercurial modules to use a custom loader.
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if sys.version_info[0] >= 3:
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from . import pure
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import importlib
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import io
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import token
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import tokenize
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class hgpathentryfinder(importlib.abc.MetaPathFinder):
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"""A sys.meta_path finder that uses a custom module loader."""
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def find_spec(self, fullname, path, target=None):
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# Only handle Mercurial-related modules.
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if not fullname.startswith(('mercurial.', 'hgext.', 'hgext3rd.')):
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return None
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# This assumes Python 3 doesn't support loading C modules.
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if fullname in _dualmodules:
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stem = fullname.split('.')[-1]
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fullname = 'mercurial.pure.%s' % stem
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target = pure
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assert len(path) == 1
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path = [os.path.join(path[0], 'pure')]
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# Try to find the module using other registered finders.
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spec = None
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for finder in sys.meta_path:
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if finder == self:
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continue
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spec = finder.find_spec(fullname, path, target=target)
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if spec:
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break
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# This is a Mercurial-related module but we couldn't find it
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# using the previously-registered finders. This likely means
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# the module doesn't exist.
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if not spec:
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return None
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if fullname.startswith('mercurial.pure.'):
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spec.name = spec.name.replace('.pure.', '.')
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# TODO need to support loaders from alternate specs, like zip
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# loaders.
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spec.loader = hgloader(spec.name, spec.origin)
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return spec
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def replacetokens(tokens):
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"""Transform a stream of tokens from raw to Python 3.
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It is called by the custom module loading machinery to rewrite
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source/tokens between source decoding and compilation.
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Returns a generator of possibly rewritten tokens.
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The input token list may be mutated as part of processing. However,
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its changes do not necessarily match the output token stream.
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REMEMBER TO CHANGE ``BYTECODEHEADER`` WHEN CHANGING THIS FUNCTION
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OR CACHED FILES WON'T GET INVALIDATED PROPERLY.
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"""
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for i, t in enumerate(tokens):
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# Convert most string literals to byte literals. String literals
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# in Python 2 are bytes. String literals in Python 3 are unicode.
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# Most strings in Mercurial are bytes and unicode strings are rare.
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# Rather than rewrite all string literals to use ``b''`` to indicate
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# byte strings, we apply this token transformer to insert the ``b``
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# prefix nearly everywhere.
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if t.type == token.STRING:
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s = t.string
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# Preserve docstrings as string literals. This is inconsistent
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# with regular unprefixed strings. However, the
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# "from __future__" parsing (which allows a module docstring to
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# exist before it) doesn't properly handle the docstring if it
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# is b''' prefixed, leading to a SyntaxError. We leave all
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# docstrings as unprefixed to avoid this. This means Mercurial
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# components touching docstrings need to handle unicode,
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# unfortunately.
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if s[0:3] in ("'''", '"""'):
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yield t
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continue
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# If the first character isn't a quote, it is likely a string
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# prefixing character (such as 'b', 'u', or 'r'. Ignore.
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if s[0] not in ("'", '"'):
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yield t
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continue
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# String literal. Prefix to make a b'' string.
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yield tokenize.TokenInfo(t.type, 'b%s' % s, t.start, t.end,
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t.line)
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continue
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try:
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nexttoken = tokens[i + 1]
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except IndexError:
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nexttoken = None
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try:
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prevtoken = tokens[i - 1]
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except IndexError:
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prevtoken = None
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# This looks like a function call.
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if (t.type == token.NAME and nexttoken and
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nexttoken.type == token.OP and nexttoken.string == '('):
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fn = t.string
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# *attr() builtins don't accept byte strings to 2nd argument.
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# Rewrite the token to include the unicode literal prefix so
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# the string transformer above doesn't add the byte prefix.
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if fn in ('getattr', 'setattr', 'hasattr', 'safehasattr'):
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try:
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# (NAME, 'getattr')
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# (OP, '(')
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# (NAME, 'foo')
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# (OP, ',')
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# (NAME|STRING, foo)
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st = tokens[i + 4]
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if (st.type == token.STRING and
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st.string[0] in ("'", '"')):
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rt = tokenize.TokenInfo(st.type, 'u%s' % st.string,
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st.start, st.end, st.line)
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tokens[i + 4] = rt
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except IndexError:
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pass
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# .encode() and .decode() on str/bytes/unicode don't accept
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# byte strings on Python 3. Rewrite the token to include the
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# unicode literal prefix so the string transformer above doesn't
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# add the byte prefix.
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if (fn in ('encode', 'decode') and
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prevtoken.type == token.OP and prevtoken.string == '.'):
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# (OP, '.')
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# (NAME, 'encode')
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# (OP, '(')
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# (STRING, 'utf-8')
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# (OP, ')')
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try:
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st = tokens[i + 2]
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if (st.type == token.STRING and
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st.string[0] in ("'", '"')):
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rt = tokenize.TokenInfo(st.type, 'u%s' % st.string,
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st.start, st.end, st.line)
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tokens[i + 2] = rt
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except IndexError:
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pass
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# Emit unmodified token.
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yield t
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# Header to add to bytecode files. This MUST be changed when
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# ``replacetoken`` or any mechanism that changes semantics of module
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# loading is changed. Otherwise cached bytecode may get loaded without
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# the new transformation mechanisms applied.
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BYTECODEHEADER = b'HG\x00\x01'
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class hgloader(importlib.machinery.SourceFileLoader):
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"""Custom module loader that transforms source code.
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When the source code is converted to a code object, we transform
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certain patterns to be Python 3 compatible. This allows us to write code
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that is natively Python 2 and compatible with Python 3 without
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making the code excessively ugly.
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We do this by transforming the token stream between parse and compile.
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Implementing transformations invalidates caching assumptions made
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by the built-in importer. The built-in importer stores a header on
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saved bytecode files indicating the Python/bytecode version. If the
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version changes, the cached bytecode is ignored. The Mercurial
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transformations could change at any time. This means we need to check
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that cached bytecode was generated with the current transformation
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code or there could be a mismatch between cached bytecode and what
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would be generated from this class.
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We supplement the bytecode caching layer by wrapping ``get_data``
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and ``set_data``. These functions are called when the
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``SourceFileLoader`` retrieves and saves bytecode cache files,
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respectively. We simply add an additional header on the file. As
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long as the version in this file is changed when semantics change,
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cached bytecode should be invalidated when transformations change.
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The added header has the form ``HG<VERSION>``. That is a literal
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``HG`` with 2 binary bytes indicating the transformation version.
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"""
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def get_data(self, path):
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data = super(hgloader, self).get_data(path)
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if not path.endswith(tuple(importlib.machinery.BYTECODE_SUFFIXES)):
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return data
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# There should be a header indicating the Mercurial transformation
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# version. If it doesn't exist or doesn't match the current version,
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# we raise an OSError because that is what
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# ``SourceFileLoader.get_code()`` expects when loading bytecode
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# paths to indicate the cached file is "bad."
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if data[0:2] != b'HG':
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raise OSError('no hg header')
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if data[0:4] != BYTECODEHEADER:
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raise OSError('hg header version mismatch')
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return data[4:]
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def set_data(self, path, data, *args, **kwargs):
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if path.endswith(tuple(importlib.machinery.BYTECODE_SUFFIXES)):
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data = BYTECODEHEADER + data
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return super(hgloader, self).set_data(path, data, *args, **kwargs)
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def source_to_code(self, data, path):
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"""Perform token transformation before compilation."""
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buf = io.BytesIO(data)
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tokens = tokenize.tokenize(buf.readline)
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data = tokenize.untokenize(replacetokens(list(tokens)))
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# Python's built-in importer strips frames from exceptions raised
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# for this code. Unfortunately, that mechanism isn't extensible
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# and our frame will be blamed for the import failure. There
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# are extremely hacky ways to do frame stripping. We haven't
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# implemented them because they are very ugly.
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return super(hgloader, self).source_to_code(data, path)
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# We automagically register our custom importer as a side-effect of loading.
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# This is necessary to ensure that any entry points are able to import
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# mercurial.* modules without having to perform this registration themselves.
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if sys.version_info[0] >= 3:
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_importercls = hgpathentryfinder
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else:
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_importercls = hgimporter
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if not any(isinstance(x, _importercls) for x in sys.meta_path):
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# meta_path is used before any implicit finders and before sys.path.
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sys.meta_path.insert(0, _importercls())
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