Fix update_query(None) doesn't clear the query

[slymit]

What do these changes do?

This fix bug when method url.update_query(None) doesn't clear the query.

Are there changes in behavior for the user?

This changes clear the query if None is passed to method update_query().

Related issue number

#723

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment into the CHANGES folder
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    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: Fix issue with non-ascii contents in doctest text files.

[mjpieters]

Instead of re-testing args, check if s == "". _get_str_query() will only ever return "" if None was passed in. We can make use of this to avoid unnecessary round-tripping the query string to MultiDict and back:

Suggested change

	s = self._get_str_query(*args, **kwargs)
	new_query = MultiDict(parse_qsl(s, keep_blank_values=True))
	query = MultiDict(self.query)
	query.update(new_query)
	if args and args[0] is None:
	query = new_query
	else:
	query = MultiDict(self.query)
	query.update(new_query)
	s, query = self._get_str_query(*args, **kwargs), None
	if s:
	new_query = MultiDict(parse_qsl(s, keep_blank_values=True))
	query = MultiDict(self.query)
	query.update(new_query)

By setting query = None at the start we save on parsing an empty string to an empty MultiDict() and back again; note that the last line uses self._get_str_query(query) again so defaulting query to None means that self._val._replace(query="") is called (where self._val is a urllib.parse.SplitResult() named tuple).

[asvetlov]

Fixed by #792 I guess