upstream/mercurial-mirror Files · mercurial/policy.py

perf: import newer modules separately for earlier Mercurial...

perf: import newer modules separately for earlier Mercurial demandimport of early Mercurial loads an imported module immediately, if a module is imported absolutely by "from a import b" style. Recent perf.py satisfies this condition, because it does: - have "from __future__ import absolute_import" line - use "from a import b" style for modules in "mercurial" package Before this patch, importing modules below prevents perf.py from being loaded by earlier Mercurial, because these aren't available in such Mercurial, even though there are some code paths for Mercurial earlier than 1.9. - branchmap 2.5 (or bcee63733aad) - repoview 2.5 (or 3a6ddacb7198) - obsolete 2.3 (or ad0d6c2b3279) - scmutil 1.9 (or 8b252e826c68) For example, setting "_prereadsize" attribute in perfindex() and perfnodelookup() is effective only with Mercurial earlier than 1.8 (or 61c9bc3da402). After this patch, "mercurial.error" is the only blocker in "from mercurial import" statement for loading perf.py with Mercurial earlier than 1.2. This patch ignores it, because just importing it separately isn't enough.

Maciej Fijalkowski - - Load All Authors

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      # policy.py - module policy logic for Mercurial.

      #

      # Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>

      #

      # This software may be used and distributed according to the terms of the

      # GNU General Public License version 2 or any later version.

      from __future__ import absolute_import

      import os

      import sys

      # Rules for how modules can be loaded. Values are:

      #

      #    c - require C extensions

      #    allow - allow pure Python implementation when C loading fails

      #    cffi - required cffi versions (implemented within pure module)

      #    cffi-allow - allow pure Python implementation if cffi version is missing

      #    py - only load pure Python modules

      #

      # By default, require the C extensions for performance reasons.

      policy = 'c'

      policynoc = ('cffi', 'cffi-allow', 'py')

      policynocffi = ('c', 'py')

      try:

          from . import __modulepolicy__

          policy = __modulepolicy__.modulepolicy

      except ImportError:

          pass

      # PyPy doesn't load C extensions.

      #

      # The canonical way to do this is to test platform.python_implementation().

      # But we don't import platform and don't bloat for it here.

      if '__pypy__' in sys.builtin_module_names:

          policy = 'cffi'

      # Our C extensions aren't yet compatible with Python 3. So use pure Python

      # on Python 3 for now.

      if sys.version_info[0] >= 3:

          policy = 'py'

      # Environment variable can always force settings.

      policy = os.environ.get('HGMODULEPOLICY', policy)

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				# policy.py - module policy logic for Mercurial.
				#
				# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>
				#
				# This software may be used and distributed according to the terms of the
				# GNU General Public License version 2 or any later version.

				from __future__ import absolute_import

				import os
				import sys

				# Rules for how modules can be loaded. Values are:
				#
				# c - require C extensions
				# allow - allow pure Python implementation when C loading fails
				# cffi - required cffi versions (implemented within pure module)
				# cffi-allow - allow pure Python implementation if cffi version is missing
				# py - only load pure Python modules
				#
				# By default, require the C extensions for performance reasons.
				policy = 'c'
				policynoc = ('cffi', 'cffi-allow', 'py')
				policynocffi = ('c', 'py')

				try:
				from . import __modulepolicy__
				policy = __modulepolicy__.modulepolicy
				except ImportError:
				pass

				# PyPy doesn't load C extensions.
				#
				# The canonical way to do this is to test platform.python_implementation().
				# But we don't import platform and don't bloat for it here.
				if '__pypy__' in sys.builtin_module_names:
				policy = 'cffi'

				# Our C extensions aren't yet compatible with Python 3. So use pure Python
				# on Python 3 for now.
				if sys.version_info[0] >= 3:
				policy = 'py'

				# Environment variable can always force settings.
				policy = os.environ.get('HGMODULEPOLICY', policy)