Don't require 'name' attribute for scrapy.Spider

I think we should make Spider.name attribute optional. The name is used by SpiderManager to find spiders, but Spider can be used without a Scrapy project. It is unnecessary boilerplate for users of runspider command or for CrawlerRunner / CrawlerProcess users.

We can also provide a default value, e.g. self.__class__.__name__, to help with discovery; this have an advantage of 1-to-1 mapping between spider class names and names printed to users - spiders can become easier to find.

Opinions?

[Gallaecio]

If and when this is done, please take into account that Spidermon currently uses spider names, for example to generate unique, spider-specific filenames for storing data in disk. You can search for spider.name there to find some of those usages.

Any change in this direction in Scrapy should probably be accompanied by the corresponding change in Spidermon.

[nyov]

Is there actually any greater value in this Spider-class name attribute? Does it make sense to put this emphasis on it, instead of simply using the Spider-class name itself? If, as @kmike says, there is only SpiderLoader using it, that code looks straightforward enough to substitute looking up the Spider-class name instead (or simply pulling in all [Base]Spider subclasses).

The only interesting case here seems to be having different classes with the same name attribute? What’s the defined behavior there, and could it be replicated by a user using python class inheritance rules instead? In which case I would downgrade this into an extension/addon feature, for whom may care, instead of trading in more magic for less importance 😉