Check context's type and return context if it is not a dict

[tark-hidden]

@aiohttp_jinja2.template('index.jinja2')
def check(request):
    param = request.match_info['param']
    if param == 'first':
        # success
        return dict(text='First case')
    elif param == 'second':
        # success
        return dict(text='Second case', user='Tark')
    elif param == 'another':
        # fail!
        # context should be mapping, not <class 'aiohttp.web_reqrep.Response'>
        return aiohttp_jinja2.render_template(
            'another.jinja2', request=request, context=dict(user='Tark', sum=0))
    elif param == 'json':
        s = dict(text='JSON', user='Tark')
        # fail!
        # context should be mapping, not <class 'aiohttp.web_reqrep.Response'>
        return web.Response(body=bytes(json.dumps(s), encoding='utf-8'),
                            content_type='application/json')
    elif param == 'redirect':
        # fail!
        # context should be mapping, not <class 'aiohttp.web_exceptions.HTTPFound'>
        return HTTPFound('http://google.com')
    return dict(text='Hello!')

It can be in a real-world project. @aiohttp_jinja2.template has been used for a few lines shorter code.
But with checking context's type in template decorator it will work and http://stackoverflow.com/questions/29322753/aiohttp-and-aiohttp-jinja2-response-error will never be asked.

[asvetlov]

1. Your check is not correct, collections.abc.Mapping is not equal to dict.
2. Currently aiohttp_jinja2 has strict checking and I don't want to relax it. At least for now.
3. Please run test suite before publishing pull request :)

[tark-hidden]

1. My bad. I thought it was exactly a dict.

2. Now with template decorator you cannot even do a redirect. It is usual case, I guess.

3. You are right, my bad again.

       if isinstance(context, web.Response):
           return context
   

Test passed!

[asvetlov]

Well, redirection is good point!
As well as raising HTTPExceptions deep inside web-handler calling chain.

[asvetlov]

Should be web.StreamResponse -- top class in responses hierarchy.

[asvetlov]

Tests are required for any pull request.

[tark-hidden]

I don't really know what should I check here... Test for checking context is response is ready.

[asvetlov]

Don't do redirect, return HTTPForbidden instead and check for status code.