"No-op" import hook

noop_import_hook.py

import imp
import inspect
import sys


__all__ = []


class PassthroughImporter(object):
    """Import hook that simulates the standard import flow
    that happens when we don't use import hooks at all.
    
    While not very useful on its own, the hook can serve as
    a template for injecting custom logic into the import process.
    """
    def find_module(self, fullname, path=None):
        if '.' in fullname:
            parent, name = fullname.rsplit('.', 1)
            find_path = self._import(parent).__path__
        else:
            name = fullname
            find_path = path

        try:
            imp.find_module(name, find_path)
        except ImportError:
            return None  # couldn't find module, let Python try next importer

        self.path = path
        return self

    def load_module(self, fullname):
        imp.acquire_lock()
        try:
            return self._import(fullname)
        finally:
            imp.release_lock()

    def _import(self, fullname):
        try:
            return sys.modules[fullname]
        except KeyError:
            pass

        # for dotted names, apply importing procedure recursively
        if '.' in fullname:
            package, module = fullname.rsplit('.', 1)
            pkg_obj = self._import(package)
            path = pkg_obj.__path__
        else:
            module = fullname
            path = self._path

        file_obj, pathname, desc = imp.find_module(module, path)
        try:
            mod_obj = imp.load_module(fullname, file_obj, pathname, desc)
            sys.modules[fullname] = mod_obj
            return mod_obj
        finally:
            if file_obj:
                file_obj.close()

    # Optional PEP302 methods

    def is_package(self, fullname):
        return hasattr(self._import(fullname), '__path__')

    def get_code(self, fullname):
        return compile(self.get_source(fullname))

    def get_source(self, fullname):
        return inspect.getsource(self._import(fullname))


sys.meta_path.append(PassthroughImporter())