Unconsistency in week Date filter

[mailhot001]

The week filter is not consistent, there is a 1 week offset when appling a date filter.
For example if you rund the DEMO.

Show the Expenses, and apply the daily interval, with the changes(weekly) display, the expenses are shown per week, as expected.

If you click on the 2017-W36 week, there will be no data shown, to show the 2017-W36 expenses you need to filter the date to 2017-W35.

I believe the proper week is 2017-W36 so there is a -1 week difference in the week date filter?

[mailhot001]

In fava/src/fava/util/date.py
there is the following function:

There is a +1 in the date defining, so if a date is ISO week no. 1 it will return week 2.
So it seem to be a wanted behavious, but fava on the display use the standard ISO week format, thus the inconsistency?

[mailhot001]

Test did not pass, confirming this is a wanted behaviour, so maybe we should change the week number display on weekly expenses display?

[yagebu]

Test did not pass, confirming this is a wanted behaviour

That's not necessarily the case - tests are like code, they have bugs too ;) The wanted behaviour here would be for frontend and backend to match up of course. IMHO both should just match what strftime does for %W (here's how the Python docs describe that: "Week number of the year (Monday as the first day of the week) as a zero-padded decimal number. All days in a new year preceding the first Monday are considered to be in week 0.".) - the frontend does that using d3-time-format, we should change the Python side to match.

[mailhot001]

Thanks for the info, I will double check the d3 to confirm it does the same as python fromisocalendar regarding week handling and summit an updated pull request afterwards.