Datasette currently has surprising special behaviour for if a table name ends in .csv - which can happen when a tool like csvs-to-sqlite creates tables that match the filename that they were imported from.

https://latest.datasette.io/fixtures/table%2Fwith%2Fslashes.csv illustrates this behaviour: it links to .csv and .json that look like this:

• https://latest.datasette.io/fixtures/table%2Fwith%2Fslashes.csv?_format=json
• https://latest.datasette.io/fixtures/table%2Fwith%2Fslashes.csv?_format=csv&_size=max

Where normally Datasette would add the .csv or .json extension to the path component of the URL (as seen on other pages such as https://latest.datasette.io/fixtures/facet_cities) here the path_with_format() function notices that there is already a . in the path and instead adds ?_format=csv to the query string instead.

The problem with this mechanism is that it's pretty surprising. Anyone writing external code to Datasette who wants to get back the .csv or .json version giving the URL to a table page will need to know about and implement this behaviour themselves. That's likely to cause all kinds of bugs in the future.