URL equality/passing None to URL.build

[PromyLOPh]

The equality operator (==, __eq__) does not work properly when passing None to URL.build. Example:

a, b = URL.build(scheme='http', host='0'), URL.build(scheme='http', host='0', fragment=None)
assert a == b # this is False
assert repr (a) == repr (b) # this is True, because "URL('http://0')" == "URL('http://0')"

Passing an empty string works as expected. This is very confusing, because repr produces exactly the same representation.

[aio-libs-bot]

GitMate.io thinks possibly related issues are #158 (Support encoded parameter in URL.build), #156 (URL.build doesn't url encode credentials), #242 (Handle path argument of URL.build, which doesn't start from /), #33 (Parse URL parameter), and #24 (TypeError in URL.with_query).

[asvetlov]

That's interesting.
URL.build declares fragment as non-optional str parameter with default to empty string.
Why do you pass None? None for the argument is a grey zone: sometimes it works but there is no any commitment for this value type.

[webknjaz]

I think None should correspond to missing fragment with no hash # symbol while empty string would be trailing hash in URL. http://some.com/url vs. http://some.com/url#

[asvetlov]

urllib.parse.urlparse doesn't distinguish http://some.com/url and http://some.com/url#.
It returns an empty string fragment for both cases.
We can return to the question if will implement a custom HTTP parser but now there is nothing to do.

[PromyLOPh]

I’m using hypothesis to generate test data. More specifically a dict which is then passed to yarl using URL.build(**dict). And I was simply assuming None would be mapped to the default value, which is apparently wrong (judging from https://yarl.readthedocs.io/en/latest/api.html#yarl.URL.fragment). This
is fine for me, however the behavior of == and repr() in this case is very confusing and thus None should either be rejected explicitly (TypeError) or silently converted to '' to prevent this situation.

[asvetlov]

TypeError sounds good to me.
Would you prepare a pull request?

[asvetlov]

Fixed by #276