georgeyk/loafer

import asyncio
import importlib
import logging
import os
import sys
from functools import wraps

logger = logging.getLogger(__name__)


def add_current_dir_to_syspath(f):

    @wraps(f)
    def wrapper(*args, **kwargs):
        current = os.getcwd()
        changed = False
        if current not in sys.path:
            sys.path.append(current)
            changed = True

        try:
            return f(*args, **kwargs)
        finally:
            # restore sys.path
            if changed is True:
                sys.path.remove(current)

    return wrapper


@add_current_dir_to_syspath
def import_callable(full_name):
    package, *name = full_name.rsplit('.', 1)
    try:
        module = importlib.import_module(package)
    except ValueError as exc:
        raise ImportError('Error trying to import {!r}'.format(full_name)) from exc

    if name:
        handler = getattr(module, name[0])
    else:
        handler = module

    if not callable(handler):
        raise ImportError('{!r} should be callable'.format(full_name))

    return handler


async def run_in_loop_or_executor(func, *args):
    if asyncio.iscoroutinefunction(func):
        logger.debug('handler is coroutine! {!r}'.format(func))
        return await func(*args)

    loop = asyncio.get_event_loop()
    logger.debug('handler will run in a separate thread: {!r}'.format(func))
    return await loop.run_in_executor(None, func, *args)