enable reload functionality when running from Python with a factory

[pmeier]

When using uvicorn.run from Python with reload=True set, one immediately hits

uvicorn/uvicorn/main.py

Lines 564 to 567 in 44a3071

	if (config.reload or config.workers > 1) and not isinstance(app, str):
	logger = logging.getLogger("uvicorn.error")
	logger.warning("You must pass the application as an import string to enable 'reload' or " "'workers'.")
	sys.exit(1)

IIUC, this was done because it is impossible to reload (or load multiple times when using multiple workers) an instance. However, this should not be a limitation if an app factory supplied. Now the factory can be called again for each reload. Loading from a string or from a factory is done back to back already:

uvicorn/uvicorn/config.py

Lines 433 to 449 in 44a3071

	try:
	self.loaded_app = import_from_string(self.app)
	except ImportFromStringError as exc:
	logger.error("Error loading ASGI app. %s" % exc)
	sys.exit(1)
	try:
	self.loaded_app = self.loaded_app()
	except TypeError as exc:
	if self.factory:
	logger.error("Error loading ASGI app factory: %s", exc)
	sys.exit(1)
	else:
	if not self.factory:
	logger.warning(
	"ASGI app factory detected. Using it, " "but please consider setting the --factory flag explicitly."
	)