Make route matched pattern groups more consistent

[simonw]

... highlights how inconsistent the way the capturing works is. Especially as_format which can be None or "" or .json or json or not used at all in the case of TableView.

datasette/tests/test_routes.py

Lines 12 to 36 in 764738d

	@pytest.mark.parametrize(
	"path,expected_class,expected_matches",
	(
	("/", "IndexView", {"as_format": ""}),
	("/foo", "DatabaseView", {"as_format": None, "db_name": "foo"}),
	("/foo.csv", "DatabaseView", {"as_format": ".csv", "db_name": "foo"}),
	("/foo.json", "DatabaseView", {"as_format": ".json", "db_name": "foo"}),
	("/foo.humbug", "DatabaseView", {"as_format": None, "db_name": "foo.humbug"}),
	("/foo/humbug", "TableView", {"db_name": "foo", "table": "humbug"}),
	("/foo/humbug.json", "TableView", {"db_name": "foo", "table": "humbug"}),
	("/foo/humbug.blah", "TableView", {"db_name": "foo", "table": "humbug"}),
	(
	"/foo/humbug/1",
	"RowView",
	{"as_format": None, "db_name": "foo", "pk_path": "1", "table": "humbug"},
	),
	(
	"/foo/humbug/1.json",
	"RowView",
	{"as_format": ".json", "db_name": "foo", "pk_path": "1", "table": "humbug"},
	),
	("/-/metadata.json", "JsonDataView", {"as_format": ".json"}),
	("/-/metadata", "JsonDataView", {"as_format": ""}),
	),
	)

Originally posted by @simonw in #1666 (comment)

Part of:

• Refactor and simplify Datasette routing and views #1660

[simonw]

I called it as_format to avoid clashing with the Python built-in format() function when these things were turned into keyword arguments, but now that they're not I can use format instead.

I think I'm going to go with database, table, format and pks.

[simonw]

OK, I've made this more consistent - I still need to address the fact that format can be .json or json or not used at all before I close this issue.

datasette/tests/test_routes.py

Lines 15 to 35 in 6141938

	("/", "IndexView", {"format": ""}),
	("/foo", "DatabaseView", {"format": None, "database": "foo"}),
	("/foo.csv", "DatabaseView", {"format": ".csv", "database": "foo"}),
	("/foo.json", "DatabaseView", {"format": ".json", "database": "foo"}),
	("/foo.humbug", "DatabaseView", {"format": None, "database": "foo.humbug"}),
	("/foo/humbug", "TableView", {"database": "foo", "table": "humbug"}),
	("/foo/humbug.json", "TableView", {"database": "foo", "table": "humbug"}),
	("/foo/humbug.blah", "TableView", {"database": "foo", "table": "humbug"}),
	(
	"/foo/humbug/1",
	"RowView",
	{"format": None, "database": "foo", "pks": "1", "table": "humbug"},
	),
	(
	"/foo/humbug/1.json",
	"RowView",
	{"format": ".json", "database": "foo", "pks": "1", "table": "humbug"},
	),
	("/-/metadata.json", "JsonDataView", {"format": ".json"}),
	("/-/metadata", "JsonDataView", {"format": ""}),
	),

[simonw]

I can now read format from request.url_vars and delete this code entirely:

datasette/datasette/views/base.py

Lines 375 to 381 in b9c2b1c

	def get_format(self, request):
	# Format is the bit from the path following the ., if one exists
	last_path_component = request.path.split("/")[-1]
	if "." in last_path_component:
	return last_path_component.split(".")[-1]
	else:
	return None