'Invalid format' error

[justb4]

Running plain pygeoapi in virtualenv Python 3.7.1 Ubuntu 18.04 and requesting any URL via the browser all requests return:

                InvalidParameterValue
                Invalid format

We expect collections etc.

Inspecting the code it appears to come out of the function pygeoapi.py: check_format(), in particular this line will return a list of accept formats so the check on this line will always fail.

Have tested and will make a PR, replacing the check_format() function with something like:

def check_format(args, headers):
    """
    check format requested from arguments or headers

    :param args: dict of request keyword value pairs
    :param headers: dict of request headers

    :returns: format value
    """

    # Optional f=html or f=json query param
    # overrides accept
    format_ = args.get('f')
    if format_:
        return format_

    # Format not specified: get from accept headers
    format_ = 'text/html'

    if 'accept' in headers.keys():
        format_ = headers['accept']
    elif 'Accept' in headers.keys():
        format_ = headers['Accept']

    format_ = format_.split(',')

    if 'text/html' in format_:
        format_ = 'html'
    elif 'application/json' in format_:
        format_ = 'json'

    return format_

This works for us, both with query parm, and even default (neither f= nor accept headers).

[justb4]

To be complete some tests need to be added in test_check_format() for "browser Accept Header" where we initially ran into and was the reason for this issue. A typical browser Accept Header may look like:

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3

A PR is a bit overkill to add lines in test_check_format() :

headers_['Accept'] = 'text/html,application/xhtml+xml,application/xml;q=0.9,'
assert check_format({}, headers_) == 'html'

headers_['accept'] = 'text/html,application/xhtml+xml,application/xml;q=0.9,'
assert check_format({}, headers_) == 'html'

[tomkralidis]

Thanks @justb4; added in 20c96a8f4756aabad60fb0a39704de2b715715c6