mirror of https://github.com/python/cpython
728 lines
25 KiB
Python
728 lines
25 KiB
Python
"""
|
|
Import utilities
|
|
|
|
Exported classes:
|
|
ImportManager Manage the import process
|
|
|
|
Importer Base class for replacing standard import functions
|
|
BuiltinImporter Emulate the import mechanism for builtin and frozen modules
|
|
|
|
DynLoadSuffixImporter
|
|
"""
|
|
|
|
# note: avoid importing non-builtin modules
|
|
import imp ### not available in JPython?
|
|
import sys
|
|
import __builtin__
|
|
|
|
# for the DirectoryImporter
|
|
import struct
|
|
import marshal
|
|
|
|
__all__ = ["ImportManager","Importer","BuiltinImporter"]
|
|
|
|
_StringType = type('')
|
|
_ModuleType = type(sys) ### doesn't work in JPython...
|
|
|
|
class ImportManager:
|
|
"Manage the import process."
|
|
|
|
def install(self, namespace=vars(__builtin__)):
|
|
"Install this ImportManager into the specified namespace."
|
|
|
|
if isinstance(namespace, _ModuleType):
|
|
namespace = vars(namespace)
|
|
|
|
# Note: we have no notion of "chaining"
|
|
|
|
# Record the previous import hook, then install our own.
|
|
self.previous_importer = namespace['__import__']
|
|
self.namespace = namespace
|
|
namespace['__import__'] = self._import_hook
|
|
|
|
### fix this
|
|
#namespace['reload'] = self._reload_hook
|
|
|
|
def uninstall(self):
|
|
"Restore the previous import mechanism."
|
|
self.namespace['__import__'] = self.previous_importer
|
|
|
|
def add_suffix(self, suffix, importFunc):
|
|
assert callable(importFunc)
|
|
self.fs_imp.add_suffix(suffix, importFunc)
|
|
|
|
######################################################################
|
|
#
|
|
# PRIVATE METHODS
|
|
#
|
|
|
|
clsFilesystemImporter = None
|
|
|
|
def __init__(self, fs_imp=None):
|
|
# we're definitely going to be importing something in the future,
|
|
# so let's just load the OS-related facilities.
|
|
if not _os_stat:
|
|
_os_bootstrap()
|
|
|
|
# This is the Importer that we use for grabbing stuff from the
|
|
# filesystem. It defines one more method (import_from_dir) for our use.
|
|
if fs_imp is None:
|
|
cls = self.clsFilesystemImporter or _FilesystemImporter
|
|
fs_imp = cls()
|
|
self.fs_imp = fs_imp
|
|
|
|
# Initialize the set of suffixes that we recognize and import.
|
|
# The default will import dynamic-load modules first, followed by
|
|
# .py files (or a .py file's cached bytecode)
|
|
for desc in imp.get_suffixes():
|
|
if desc[2] == imp.C_EXTENSION:
|
|
self.add_suffix(desc[0],
|
|
DynLoadSuffixImporter(desc).import_file)
|
|
self.add_suffix('.py', py_suffix_importer)
|
|
|
|
def _import_hook(self, fqname, globals=None, locals=None, fromlist=None):
|
|
"""Python calls this hook to locate and import a module."""
|
|
|
|
parts = fqname.split('.')
|
|
|
|
# determine the context of this import
|
|
parent = self._determine_import_context(globals)
|
|
|
|
# if there is a parent, then its importer should manage this import
|
|
if parent:
|
|
module = parent.__importer__._do_import(parent, parts, fromlist)
|
|
if module:
|
|
return module
|
|
|
|
# has the top module already been imported?
|
|
try:
|
|
top_module = sys.modules[parts[0]]
|
|
except KeyError:
|
|
|
|
# look for the topmost module
|
|
top_module = self._import_top_module(parts[0])
|
|
if not top_module:
|
|
# the topmost module wasn't found at all.
|
|
raise ImportError, 'No module named ' + fqname
|
|
|
|
# fast-path simple imports
|
|
if len(parts) == 1:
|
|
if not fromlist:
|
|
return top_module
|
|
|
|
if not top_module.__dict__.get('__ispkg__'):
|
|
# __ispkg__ isn't defined (the module was not imported by us),
|
|
# or it is zero.
|
|
#
|
|
# In the former case, there is no way that we could import
|
|
# sub-modules that occur in the fromlist (but we can't raise an
|
|
# error because it may just be names) because we don't know how
|
|
# to deal with packages that were imported by other systems.
|
|
#
|
|
# In the latter case (__ispkg__ == 0), there can't be any sub-
|
|
# modules present, so we can just return.
|
|
#
|
|
# In both cases, since len(parts) == 1, the top_module is also
|
|
# the "bottom" which is the defined return when a fromlist
|
|
# exists.
|
|
return top_module
|
|
|
|
importer = top_module.__dict__.get('__importer__')
|
|
if importer:
|
|
return importer._finish_import(top_module, parts[1:], fromlist)
|
|
|
|
# Grrr, some people "import os.path" or do "from os.path import ..."
|
|
if len(parts) == 2 and hasattr(top_module, parts[1]):
|
|
if fromlist:
|
|
return getattr(top_module, parts[1])
|
|
else:
|
|
return top_module
|
|
|
|
# If the importer does not exist, then we have to bail. A missing
|
|
# importer means that something else imported the module, and we have
|
|
# no knowledge of how to get sub-modules out of the thing.
|
|
raise ImportError, 'No module named ' + fqname
|
|
|
|
def _determine_import_context(self, globals):
|
|
"""Returns the context in which a module should be imported.
|
|
|
|
The context could be a loaded (package) module and the imported module
|
|
will be looked for within that package. The context could also be None,
|
|
meaning there is no context -- the module should be looked for as a
|
|
"top-level" module.
|
|
"""
|
|
|
|
if not globals or not globals.get('__importer__'):
|
|
# globals does not refer to one of our modules or packages. That
|
|
# implies there is no relative import context (as far as we are
|
|
# concerned), and it should just pick it off the standard path.
|
|
return None
|
|
|
|
# The globals refer to a module or package of ours. It will define
|
|
# the context of the new import. Get the module/package fqname.
|
|
parent_fqname = globals['__name__']
|
|
|
|
# if a package is performing the import, then return itself (imports
|
|
# refer to pkg contents)
|
|
if globals['__ispkg__']:
|
|
parent = sys.modules[parent_fqname]
|
|
assert globals is parent.__dict__
|
|
return parent
|
|
|
|
i = parent_fqname.rfind('.')
|
|
|
|
# a module outside of a package has no particular import context
|
|
if i == -1:
|
|
return None
|
|
|
|
# if a module in a package is performing the import, then return the
|
|
# package (imports refer to siblings)
|
|
parent_fqname = parent_fqname[:i]
|
|
parent = sys.modules[parent_fqname]
|
|
assert parent.__name__ == parent_fqname
|
|
return parent
|
|
|
|
def _import_top_module(self, name):
|
|
# scan sys.path looking for a location in the filesystem that contains
|
|
# the module, or an Importer object that can import the module.
|
|
for item in sys.path:
|
|
if isinstance(item, _StringType):
|
|
module = self.fs_imp.import_from_dir(item, name)
|
|
else:
|
|
module = item.import_top(name)
|
|
if module:
|
|
return module
|
|
return None
|
|
|
|
def _reload_hook(self, module):
|
|
"Python calls this hook to reload a module."
|
|
|
|
# reloading of a module may or may not be possible (depending on the
|
|
# importer), but at least we can validate that it's ours to reload
|
|
importer = module.__dict__.get('__importer__')
|
|
if not importer:
|
|
### oops. now what...
|
|
pass
|
|
|
|
# okay. it is using the imputil system, and we must delegate it, but
|
|
# we don't know what to do (yet)
|
|
### we should blast the module dict and do another get_code(). need to
|
|
### flesh this out and add proper docco...
|
|
raise SystemError, "reload not yet implemented"
|
|
|
|
|
|
class Importer:
|
|
"Base class for replacing standard import functions."
|
|
|
|
def import_top(self, name):
|
|
"Import a top-level module."
|
|
return self._import_one(None, name, name)
|
|
|
|
######################################################################
|
|
#
|
|
# PRIVATE METHODS
|
|
#
|
|
def _finish_import(self, top, parts, fromlist):
|
|
# if "a.b.c" was provided, then load the ".b.c" portion down from
|
|
# below the top-level module.
|
|
bottom = self._load_tail(top, parts)
|
|
|
|
# if the form is "import a.b.c", then return "a"
|
|
if not fromlist:
|
|
# no fromlist: return the top of the import tree
|
|
return top
|
|
|
|
# the top module was imported by self.
|
|
#
|
|
# this means that the bottom module was also imported by self (just
|
|
# now, or in the past and we fetched it from sys.modules).
|
|
#
|
|
# since we imported/handled the bottom module, this means that we can
|
|
# also handle its fromlist (and reliably use __ispkg__).
|
|
|
|
# if the bottom node is a package, then (potentially) import some
|
|
# modules.
|
|
#
|
|
# note: if it is not a package, then "fromlist" refers to names in
|
|
# the bottom module rather than modules.
|
|
# note: for a mix of names and modules in the fromlist, we will
|
|
# import all modules and insert those into the namespace of
|
|
# the package module. Python will pick up all fromlist names
|
|
# from the bottom (package) module; some will be modules that
|
|
# we imported and stored in the namespace, others are expected
|
|
# to be present already.
|
|
if bottom.__ispkg__:
|
|
self._import_fromlist(bottom, fromlist)
|
|
|
|
# if the form is "from a.b import c, d" then return "b"
|
|
return bottom
|
|
|
|
def _import_one(self, parent, modname, fqname):
|
|
"Import a single module."
|
|
|
|
# has the module already been imported?
|
|
try:
|
|
return sys.modules[fqname]
|
|
except KeyError:
|
|
pass
|
|
|
|
# load the module's code, or fetch the module itself
|
|
result = self.get_code(parent, modname, fqname)
|
|
if result is None:
|
|
return None
|
|
|
|
module = self._process_result(result, fqname)
|
|
|
|
# insert the module into its parent
|
|
if parent:
|
|
setattr(parent, modname, module)
|
|
return module
|
|
|
|
def _process_result(self, (ispkg, code, values), fqname):
|
|
# did get_code() return an actual module? (rather than a code object)
|
|
is_module = isinstance(code, _ModuleType)
|
|
|
|
# use the returned module, or create a new one to exec code into
|
|
if is_module:
|
|
module = code
|
|
else:
|
|
module = imp.new_module(fqname)
|
|
|
|
### record packages a bit differently??
|
|
module.__importer__ = self
|
|
module.__ispkg__ = ispkg
|
|
|
|
# insert additional values into the module (before executing the code)
|
|
module.__dict__.update(values)
|
|
|
|
# the module is almost ready... make it visible
|
|
sys.modules[fqname] = module
|
|
|
|
# execute the code within the module's namespace
|
|
if not is_module:
|
|
try:
|
|
exec(code, module.__dict__)
|
|
except:
|
|
if fqname in sys.modules:
|
|
del sys.modules[fqname]
|
|
raise
|
|
|
|
# fetch from sys.modules instead of returning module directly.
|
|
# also make module's __name__ agree with fqname, in case
|
|
# the "exec code in module.__dict__" played games on us.
|
|
module = sys.modules[fqname]
|
|
module.__name__ = fqname
|
|
return module
|
|
|
|
def _load_tail(self, m, parts):
|
|
"""Import the rest of the modules, down from the top-level module.
|
|
|
|
Returns the last module in the dotted list of modules.
|
|
"""
|
|
for part in parts:
|
|
fqname = "%s.%s" % (m.__name__, part)
|
|
m = self._import_one(m, part, fqname)
|
|
if not m:
|
|
raise ImportError, "No module named " + fqname
|
|
return m
|
|
|
|
def _import_fromlist(self, package, fromlist):
|
|
'Import any sub-modules in the "from" list.'
|
|
|
|
# if '*' is present in the fromlist, then look for the '__all__'
|
|
# variable to find additional items (modules) to import.
|
|
if '*' in fromlist:
|
|
fromlist = list(fromlist) + \
|
|
list(package.__dict__.get('__all__', []))
|
|
|
|
for sub in fromlist:
|
|
# if the name is already present, then don't try to import it (it
|
|
# might not be a module!).
|
|
if sub != '*' and not hasattr(package, sub):
|
|
subname = "%s.%s" % (package.__name__, sub)
|
|
submod = self._import_one(package, sub, subname)
|
|
if not submod:
|
|
raise ImportError, "cannot import name " + subname
|
|
|
|
def _do_import(self, parent, parts, fromlist):
|
|
"""Attempt to import the module relative to parent.
|
|
|
|
This method is used when the import context specifies that <self>
|
|
imported the parent module.
|
|
"""
|
|
top_name = parts[0]
|
|
top_fqname = parent.__name__ + '.' + top_name
|
|
top_module = self._import_one(parent, top_name, top_fqname)
|
|
if not top_module:
|
|
# this importer and parent could not find the module (relatively)
|
|
return None
|
|
|
|
return self._finish_import(top_module, parts[1:], fromlist)
|
|
|
|
######################################################################
|
|
#
|
|
# METHODS TO OVERRIDE
|
|
#
|
|
def get_code(self, parent, modname, fqname):
|
|
"""Find and retrieve the code for the given module.
|
|
|
|
parent specifies a parent module to define a context for importing. It
|
|
may be None, indicating no particular context for the search.
|
|
|
|
modname specifies a single module (not dotted) within the parent.
|
|
|
|
fqname specifies the fully-qualified module name. This is a
|
|
(potentially) dotted name from the "root" of the module namespace
|
|
down to the modname.
|
|
If there is no parent, then modname==fqname.
|
|
|
|
This method should return None, or a 3-tuple.
|
|
|
|
* If the module was not found, then None should be returned.
|
|
|
|
* The first item of the 2- or 3-tuple should be the integer 0 or 1,
|
|
specifying whether the module that was found is a package or not.
|
|
|
|
* The second item is the code object for the module (it will be
|
|
executed within the new module's namespace). This item can also
|
|
be a fully-loaded module object (e.g. loaded from a shared lib).
|
|
|
|
* The third item is a dictionary of name/value pairs that will be
|
|
inserted into new module before the code object is executed. This
|
|
is provided in case the module's code expects certain values (such
|
|
as where the module was found). When the second item is a module
|
|
object, then these names/values will be inserted *after* the module
|
|
has been loaded/initialized.
|
|
"""
|
|
raise RuntimeError, "get_code not implemented"
|
|
|
|
|
|
######################################################################
|
|
#
|
|
# Some handy stuff for the Importers
|
|
#
|
|
|
|
# byte-compiled file suffix character
|
|
_suffix_char = __debug__ and 'c' or 'o'
|
|
|
|
# byte-compiled file suffix
|
|
_suffix = '.py' + _suffix_char
|
|
|
|
def _compile(pathname, timestamp):
|
|
"""Compile (and cache) a Python source file.
|
|
|
|
The file specified by <pathname> is compiled to a code object and
|
|
returned.
|
|
|
|
Presuming the appropriate privileges exist, the bytecodes will be
|
|
saved back to the filesystem for future imports. The source file's
|
|
modification timestamp must be provided as a Long value.
|
|
"""
|
|
codestring = open(pathname, 'rU').read()
|
|
if codestring and codestring[-1] != '\n':
|
|
codestring = codestring + '\n'
|
|
code = __builtin__.compile(codestring, pathname, 'exec')
|
|
|
|
# try to cache the compiled code
|
|
try:
|
|
f = open(pathname + _suffix_char, 'wb')
|
|
except IOError:
|
|
pass
|
|
else:
|
|
f.write('\0\0\0\0')
|
|
f.write(struct.pack('<I', timestamp))
|
|
marshal.dump(code, f)
|
|
f.flush()
|
|
f.seek(0, 0)
|
|
f.write(imp.get_magic())
|
|
f.close()
|
|
|
|
return code
|
|
|
|
_os_stat = _os_path_join = None
|
|
def _os_bootstrap():
|
|
"Set up 'os' module replacement functions for use during import bootstrap."
|
|
|
|
names = sys.builtin_module_names
|
|
|
|
join = None
|
|
if 'posix' in names:
|
|
sep = '/'
|
|
from posix import stat
|
|
elif 'nt' in names:
|
|
sep = '\\'
|
|
from nt import stat
|
|
elif 'dos' in names:
|
|
sep = '\\'
|
|
from dos import stat
|
|
elif 'os2' in names:
|
|
sep = '\\'
|
|
from os2 import stat
|
|
elif 'mac' in names:
|
|
from mac import stat
|
|
def join(a, b):
|
|
if a == '':
|
|
return b
|
|
if ':' not in a:
|
|
a = ':' + a
|
|
if a[-1:] != ':':
|
|
a = a + ':'
|
|
return a + b
|
|
else:
|
|
raise ImportError, 'no os specific module found'
|
|
|
|
if join is None:
|
|
def join(a, b, sep=sep):
|
|
if a == '':
|
|
return b
|
|
lastchar = a[-1:]
|
|
if lastchar == '/' or lastchar == sep:
|
|
return a + b
|
|
return a + sep + b
|
|
|
|
global _os_stat
|
|
_os_stat = stat
|
|
|
|
global _os_path_join
|
|
_os_path_join = join
|
|
|
|
def _os_path_isdir(pathname):
|
|
"Local replacement for os.path.isdir()."
|
|
try:
|
|
s = _os_stat(pathname)
|
|
except OSError:
|
|
return None
|
|
return (s.st_mode & 0170000) == 0040000
|
|
|
|
def _timestamp(pathname):
|
|
"Return the file modification time as a Long."
|
|
try:
|
|
s = _os_stat(pathname)
|
|
except OSError:
|
|
return None
|
|
return int(s.st_mtime)
|
|
|
|
|
|
######################################################################
|
|
#
|
|
# Emulate the import mechanism for builtin and frozen modules
|
|
#
|
|
class BuiltinImporter(Importer):
|
|
def get_code(self, parent, modname, fqname):
|
|
if parent:
|
|
# these modules definitely do not occur within a package context
|
|
return None
|
|
|
|
# look for the module
|
|
if imp.is_builtin(modname):
|
|
type = imp.C_BUILTIN
|
|
elif imp.is_frozen(modname):
|
|
type = imp.PY_FROZEN
|
|
else:
|
|
# not found
|
|
return None
|
|
|
|
# got it. now load and return it.
|
|
module = imp.load_module(modname, None, modname, ('', '', type))
|
|
return 0, module, { }
|
|
|
|
|
|
######################################################################
|
|
#
|
|
# Internal importer used for importing from the filesystem
|
|
#
|
|
class _FilesystemImporter(Importer):
|
|
def __init__(self):
|
|
self.suffixes = [ ]
|
|
|
|
def add_suffix(self, suffix, importFunc):
|
|
assert callable(importFunc)
|
|
self.suffixes.append((suffix, importFunc))
|
|
|
|
def import_from_dir(self, dir, fqname):
|
|
result = self._import_pathname(_os_path_join(dir, fqname), fqname)
|
|
if result:
|
|
return self._process_result(result, fqname)
|
|
return None
|
|
|
|
def get_code(self, parent, modname, fqname):
|
|
# This importer is never used with an empty parent. Its existence is
|
|
# private to the ImportManager. The ImportManager uses the
|
|
# import_from_dir() method to import top-level modules/packages.
|
|
# This method is only used when we look for a module within a package.
|
|
assert parent
|
|
|
|
return self._import_pathname(_os_path_join(parent.__pkgdir__, modname),
|
|
fqname)
|
|
|
|
def _import_pathname(self, pathname, fqname):
|
|
if _os_path_isdir(pathname):
|
|
result = self._import_pathname(_os_path_join(pathname, '__init__'),
|
|
fqname)
|
|
if result:
|
|
values = result[2]
|
|
values['__pkgdir__'] = pathname
|
|
values['__path__'] = [ pathname ]
|
|
return 1, result[1], values
|
|
return None
|
|
|
|
for suffix, importFunc in self.suffixes:
|
|
filename = pathname + suffix
|
|
try:
|
|
finfo = _os_stat(filename)
|
|
except OSError:
|
|
pass
|
|
else:
|
|
return importFunc(filename, finfo, fqname)
|
|
return None
|
|
|
|
######################################################################
|
|
#
|
|
# SUFFIX-BASED IMPORTERS
|
|
#
|
|
|
|
def py_suffix_importer(filename, finfo, fqname):
|
|
file = filename[:-3] + _suffix
|
|
t_py = int(finfo[8])
|
|
t_pyc = _timestamp(file)
|
|
|
|
code = None
|
|
if t_pyc is not None and t_pyc >= t_py:
|
|
f = open(file, 'rb')
|
|
if f.read(4) == imp.get_magic():
|
|
t = struct.unpack('<I', f.read(4))[0]
|
|
if t == t_py:
|
|
code = marshal.load(f)
|
|
f.close()
|
|
if code is None:
|
|
file = filename
|
|
code = _compile(file, t_py)
|
|
|
|
return 0, code, { '__file__' : file }
|
|
|
|
class DynLoadSuffixImporter:
|
|
def __init__(self, desc):
|
|
self.desc = desc
|
|
|
|
def import_file(self, filename, finfo, fqname):
|
|
fp = open(filename, self.desc[1])
|
|
module = imp.load_module(fqname, fp, filename, self.desc)
|
|
module.__file__ = filename
|
|
return 0, module, { }
|
|
|
|
|
|
######################################################################
|
|
|
|
def _print_importers():
|
|
items = sys.modules.items()
|
|
items.sort()
|
|
for name, module in items:
|
|
if module:
|
|
print(name, module.__dict__.get('__importer__', '-- no importer'))
|
|
else:
|
|
print(name, '-- non-existent module')
|
|
|
|
def _test_revamp():
|
|
ImportManager().install()
|
|
sys.path.insert(0, BuiltinImporter())
|
|
|
|
######################################################################
|
|
|
|
#
|
|
# TODO
|
|
#
|
|
# from Finn Bock:
|
|
# type(sys) is not a module in JPython. what to use instead?
|
|
# imp.C_EXTENSION is not in JPython. same for get_suffixes and new_module
|
|
#
|
|
# given foo.py of:
|
|
# import sys
|
|
# sys.modules['foo'] = sys
|
|
#
|
|
# ---- standard import mechanism
|
|
# >>> import foo
|
|
# >>> foo
|
|
# <module 'sys' (built-in)>
|
|
#
|
|
# ---- revamped import mechanism
|
|
# >>> import imputil
|
|
# >>> imputil._test_revamp()
|
|
# >>> import foo
|
|
# >>> foo
|
|
# <module 'foo' from 'foo.py'>
|
|
#
|
|
#
|
|
# from MAL:
|
|
# should BuiltinImporter exist in sys.path or hard-wired in ImportManager?
|
|
# need __path__ processing
|
|
# performance
|
|
# move chaining to a subclass [gjs: it's been nuked]
|
|
# deinstall should be possible
|
|
# query mechanism needed: is a specific Importer installed?
|
|
# py/pyc/pyo piping hooks to filter/process these files
|
|
# wish list:
|
|
# distutils importer hooked to list of standard Internet repositories
|
|
# module->file location mapper to speed FS-based imports
|
|
# relative imports
|
|
# keep chaining so that it can play nice with other import hooks
|
|
#
|
|
# from Gordon:
|
|
# push MAL's mapper into sys.path[0] as a cache (hard-coded for apps)
|
|
#
|
|
# from Guido:
|
|
# need to change sys.* references for rexec environs
|
|
# need hook for MAL's walk-me-up import strategy, or Tim's absolute strategy
|
|
# watch out for sys.modules[...] is None
|
|
# flag to force absolute imports? (speeds _determine_import_context and
|
|
# checking for a relative module)
|
|
# insert names of archives into sys.path (see quote below)
|
|
# note: reload does NOT blast module dict
|
|
# shift import mechanisms and policies around; provide for hooks, overrides
|
|
# (see quote below)
|
|
# add get_source stuff
|
|
# get_topcode and get_subcode
|
|
# CRLF handling in _compile
|
|
# race condition in _compile
|
|
# refactoring of os.py to deal with _os_bootstrap problem
|
|
# any special handling to do for importing a module with a SyntaxError?
|
|
# (e.g. clean up the traceback)
|
|
# implement "domain" for path-type functionality using pkg namespace
|
|
# (rather than FS-names like __path__)
|
|
# don't use the word "private"... maybe "internal"
|
|
#
|
|
#
|
|
# Guido's comments on sys.path caching:
|
|
#
|
|
# We could cache this in a dictionary: the ImportManager can have a
|
|
# cache dict mapping pathnames to importer objects, and a separate
|
|
# method for coming up with an importer given a pathname that's not yet
|
|
# in the cache. The method should do a stat and/or look at the
|
|
# extension to decide which importer class to use; you can register new
|
|
# importer classes by registering a suffix or a Boolean function, plus a
|
|
# class. If you register a new importer class, the cache is zapped.
|
|
# The cache is independent from sys.path (but maintained per
|
|
# ImportManager instance) so that rearrangements of sys.path do the
|
|
# right thing. If a path is dropped from sys.path the corresponding
|
|
# cache entry is simply no longer used.
|
|
#
|
|
# My/Guido's comments on factoring ImportManager and Importer:
|
|
#
|
|
# > However, we still have a tension occurring here:
|
|
# >
|
|
# > 1) implementing policy in ImportManager assists in single-point policy
|
|
# > changes for app/rexec situations
|
|
# > 2) implementing policy in Importer assists in package-private policy
|
|
# > changes for normal, operating conditions
|
|
# >
|
|
# > I'll see if I can sort out a way to do this. Maybe the Importer class will
|
|
# > implement the methods (which can be overridden to change policy) by
|
|
# > delegating to ImportManager.
|
|
#
|
|
# Maybe also think about what kind of policies an Importer would be
|
|
# likely to want to change. I have a feeling that a lot of the code
|
|
# there is actually not so much policy but a *necessity* to get things
|
|
# working given the calling conventions for the __import__ hook: whether
|
|
# to return the head or tail of a dotted name, or when to do the "finish
|
|
# fromlist" stuff.
|
|
#
|