Allow to add custom metadata to Response

[kmike]

Currently it is not possible to attach a custom attribute to Response in a middleware because replace method won't keep it. There are workarounds (e.g. putting objects to response.flags), but they are ugly.

What do you think about adding an attribute to Response where user can put anything, similar to Request.meta?

[kmike]

Almost the same issue: #1453

[kmike]

One workaround is to create custom Response subclasses and use response.replace(cls=MyCustomResponse) in a middleware.

The problem with this solution is that Scrapy sometimes constructs responses by itself, e.g. when retreiving from HTTP cache or when handling decompression. In this case original response class gets forgotten.

[joeharrison714]

I'd like to try to implement this, does anyone have any newer thoughts about it that could lead me in the right direction?

[Gallaecio]

#5131 seems to address this when defining Response.attributes and using it from replace.