diff hgdemandimport/demandimportpy2.py @ 32420:0906b85bf222

demandimport: move to separate package

In Python 3, demand loading is per-package. Keeping demandimport in the
mercurial package would disable demand loading for any modules in
mercurial.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgdemandimport/demandimportpy2.py	Sun May 21 12:10:53 2017 -0700
@@ -0,0 +1,332 @@
+# demandimport.py - global demand-loading of modules for Mercurial
+#
+# Copyright 2006, 2007 Matt Mackall <[e-mail]>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+'''
+demandimport - automatic demandloading of modules
+
+To enable this module, do:
+
+  import demandimport; demandimport.enable()
+
+Imports of the following forms will be demand-loaded:
+
+  import a, b.c
+  import a.b as c
+  from a import b,c # a will be loaded immediately
+
+These imports will not be delayed:
+
+  from a import *
+  b = __import__(a)
+'''
+
+from __future__ import absolute_import
+
+import contextlib
+import os
+import sys
+
+# __builtin__ in Python 2, builtins in Python 3.
+try:
+    import __builtin__ as builtins
+except ImportError:
+    import builtins
+
+contextmanager = contextlib.contextmanager
+
+_origimport = __import__
+
+nothing = object()
+
+# Python 3 doesn't have relative imports nor level -1.
+level = -1
+if sys.version_info[0] >= 3:
+    level = 0
+_import = _origimport
+
+def _hgextimport(importfunc, name, globals, *args, **kwargs):
+    try:
+        return importfunc(name, globals, *args, **kwargs)
+    except ImportError:
+        if not globals:
+            raise
+        # extensions are loaded with "hgext_" prefix
+        hgextname = 'hgext_%s' % name
+        nameroot = hgextname.split('.', 1)[0]
+        contextroot = globals.get('__name__', '').split('.', 1)[0]
+        if nameroot != contextroot:
+            raise
+        # retry to import with "hgext_" prefix
+        return importfunc(hgextname, globals, *args, **kwargs)
+
+class _demandmod(object):
+    """module demand-loader and proxy
+
+    Specify 1 as 'level' argument at construction, to import module
+    relatively.
+    """
+    def __init__(self, name, globals, locals, level):
+        if '.' in name:
+            head, rest = name.split('.', 1)
+            after = [rest]
+        else:
+            head = name
+            after = []
+        object.__setattr__(self, r"_data",
+                           (head, globals, locals, after, level, set()))
+        object.__setattr__(self, r"_module", None)
+    def _extend(self, name):
+        """add to the list of submodules to load"""
+        self._data[3].append(name)
+
+    def _addref(self, name):
+        """Record that the named module ``name`` imports this module.
+
+        References to this proxy class having the name of this module will be
+        replaced at module load time. We assume the symbol inside the importing
+        module is identical to the "head" name of this module. We don't
+        actually know if "as X" syntax is being used to change the symbol name
+        because this information isn't exposed to __import__.
+        """
+        self._data[5].add(name)
+
+    def _load(self):
+        if not self._module:
+            head, globals, locals, after, level, modrefs = self._data
+            mod = _hgextimport(_import, head, globals, locals, None, level)
+            if mod is self:
+                # In this case, _hgextimport() above should imply
+                # _demandimport(). Otherwise, _hgextimport() never
+                # returns _demandmod. This isn't intentional behavior,
+                # in fact. (see also issue5304 for detail)
+                #
+                # If self._module is already bound at this point, self
+                # should be already _load()-ed while _hgextimport().
+                # Otherwise, there is no way to import actual module
+                # as expected, because (re-)invoking _hgextimport()
+                # should cause same result.
+                # This is reason why _load() returns without any more
+                # setup but assumes self to be already bound.
+                mod = self._module
+                assert mod and mod is not self, "%s, %s" % (self, mod)
+                return
+
+            # load submodules
+            def subload(mod, p):
+                h, t = p, None
+                if '.' in p:
+                    h, t = p.split('.', 1)
+                if getattr(mod, h, nothing) is nothing:
+                    setattr(mod, h, _demandmod(p, mod.__dict__, mod.__dict__,
+                                               level=1))
+                elif t:
+                    subload(getattr(mod, h), t)
+
+            for x in after:
+                subload(mod, x)
+
+            # Replace references to this proxy instance with the actual module.
+            if locals and locals.get(head) == self:
+                locals[head] = mod
+
+            for modname in modrefs:
+                modref = sys.modules.get(modname, None)
+                if modref and getattr(modref, head, None) == self:
+                    setattr(modref, head, mod)
+
+            object.__setattr__(self, r"_module", mod)
+
+    def __repr__(self):
+        if self._module:
+            return "<proxied module '%s'>" % self._data[0]
+        return "<unloaded module '%s'>" % self._data[0]
+    def __call__(self, *args, **kwargs):
+        raise TypeError("%s object is not callable" % repr(self))
+    def __getattribute__(self, attr):
+        if attr in ('_data', '_extend', '_load', '_module', '_addref'):
+            return object.__getattribute__(self, attr)
+        self._load()
+        return getattr(self._module, attr)
+    def __setattr__(self, attr, val):
+        self._load()
+        setattr(self._module, attr, val)
+
+_pypy = '__pypy__' in sys.builtin_module_names
+
+def _demandimport(name, globals=None, locals=None, fromlist=None, level=level):
+    if locals is None or name in ignore or fromlist == ('*',):
+        # these cases we can't really delay
+        return _hgextimport(_import, name, globals, locals, fromlist, level)
+    elif not fromlist:
+        # import a [as b]
+        if '.' in name: # a.b
+            base, rest = name.split('.', 1)
+            # email.__init__ loading email.mime
+            if globals and globals.get('__name__', None) == base:
+                return _import(name, globals, locals, fromlist, level)
+            # if a is already demand-loaded, add b to its submodule list
+            if base in locals:
+                if isinstance(locals[base], _demandmod):
+                    locals[base]._extend(rest)
+                return locals[base]
+        return _demandmod(name, globals, locals, level)
+    else:
+        # There is a fromlist.
+        # from a import b,c,d
+        # from . import b,c,d
+        # from .a import b,c,d
+
+        # level == -1: relative and absolute attempted (Python 2 only).
+        # level >= 0: absolute only (Python 2 w/ absolute_import and Python 3).
+        # The modern Mercurial convention is to use absolute_import everywhere,
+        # so modern Mercurial code will have level >= 0.
+
+        # The name of the module the import statement is located in.
+        globalname = globals.get('__name__')
+
+        def processfromitem(mod, attr):
+            """Process an imported symbol in the import statement.
+
+            If the symbol doesn't exist in the parent module, and if the
+            parent module is a package, it must be a module. We set missing
+            modules up as _demandmod instances.
+            """
+            symbol = getattr(mod, attr, nothing)
+            nonpkg = getattr(mod, '__path__', nothing) is nothing
+            if symbol is nothing:
+                if nonpkg:
+                    # do not try relative import, which would raise ValueError,
+                    # and leave unknown attribute as the default __import__()
+                    # would do. the missing attribute will be detected later
+                    # while processing the import statement.
+                    return
+                mn = '%s.%s' % (mod.__name__, attr)
+                if mn in ignore:
+                    importfunc = _origimport
+                else:
+                    importfunc = _demandmod
+                symbol = importfunc(attr, mod.__dict__, locals, level=1)
+                setattr(mod, attr, symbol)
+
+            # Record the importing module references this symbol so we can
+            # replace the symbol with the actual module instance at load
+            # time.
+            if globalname and isinstance(symbol, _demandmod):
+                symbol._addref(globalname)
+
+        def chainmodules(rootmod, modname):
+            # recurse down the module chain, and return the leaf module
+            mod = rootmod
+            for comp in modname.split('.')[1:]:
+                if getattr(mod, comp, nothing) is nothing:
+                    setattr(mod, comp, _demandmod(comp, mod.__dict__,
+                                                  mod.__dict__, level=1))
+                mod = getattr(mod, comp)
+            return mod
+
+        if level >= 0:
+            if name:
+                # "from a import b" or "from .a import b" style
+                rootmod = _hgextimport(_origimport, name, globals, locals,
+                                       level=level)
+                mod = chainmodules(rootmod, name)
+            elif _pypy:
+                # PyPy's __import__ throws an exception if invoked
+                # with an empty name and no fromlist.  Recreate the
+                # desired behaviour by hand.
+                mn = globalname
+                mod = sys.modules[mn]
+                if getattr(mod, '__path__', nothing) is nothing:
+                    mn = mn.rsplit('.', 1)[0]
+                    mod = sys.modules[mn]
+                if level > 1:
+                    mn = mn.rsplit('.', level - 1)[0]
+                    mod = sys.modules[mn]
+            else:
+                mod = _hgextimport(_origimport, name, globals, locals,
+                                   level=level)
+
+            for x in fromlist:
+                processfromitem(mod, x)
+
+            return mod
+
+        # But, we still need to support lazy loading of standard library and 3rd
+        # party modules. So handle level == -1.
+        mod = _hgextimport(_origimport, name, globals, locals)
+        mod = chainmodules(mod, name)
+
+        for x in fromlist:
+            processfromitem(mod, x)
+
+        return mod
+
+ignore = [
+    '__future__',
+    '_hashlib',
+    # ImportError during pkg_resources/__init__.py:fixup_namespace_package
+    '_imp',
+    '_xmlplus',
+    'fcntl',
+    'nt', # pathlib2 tests the existence of built-in 'nt' module
+    'win32com.gen_py',
+    'win32com.shell', # 'appdirs' tries to import win32com.shell
+    '_winreg', # 2.7 mimetypes needs immediate ImportError
+    'pythoncom',
+    # imported by tarfile, not available under Windows
+    'pwd',
+    'grp',
+    # imported by profile, itself imported by hotshot.stats,
+    # not available under Windows
+    'resource',
+    # this trips up many extension authors
+    'gtk',
+    # setuptools' pkg_resources.py expects "from __main__ import x" to
+    # raise ImportError if x not defined
+    '__main__',
+    '_ssl', # conditional imports in the stdlib, issue1964
+    '_sre', # issue4920
+    'rfc822',
+    'mimetools',
+    'sqlalchemy.events', # has import-time side effects (issue5085)
+    # setuptools 8 expects this module to explode early when not on windows
+    'distutils.msvc9compiler',
+    '__builtin__',
+    'builtins',
+    'urwid.command_map', # for pudb
+    ]
+
+if _pypy:
+    ignore.extend([
+        # _ctypes.pointer is shadowed by "from ... import pointer" (PyPy 5)
+        '_ctypes.pointer',
+    ])
+
+def isenabled():
+    return builtins.__import__ == _demandimport
+
+def enable():
+    "enable global demand-loading of modules"
+    if os.environ.get('HGDEMANDIMPORT') != 'disable':
+        builtins.__import__ = _demandimport
+
+def disable():
+    "disable global demand-loading of modules"
+    builtins.__import__ = _origimport
+
+@contextmanager
+def deactivated():
+    "context manager for disabling demandimport in 'with' blocks"
+    demandenabled = isenabled()
+    if demandenabled:
+        disable()
+
+    try:
+        yield
+    finally:
+        if demandenabled:
+            enable()