This is paving the way to move the standard filters into Rust.
Non-empty fields are now determined in Rust, using a single regex
instead of the overkill stripHTMLMedia(). The old implementation
has been moved into the Pystache code for now.
This extends the existing Rust code to handle conditional
replacement. The replacement of field names and filters to text
remains in Python, so that add-ons can still define their own
field modifiers.
The code is currently running the old Pystache rendering and the
new implementation in parallel, and will print a message to the
console if they don't match. If you notice any problems, please
let me know.
The previous implementation interpreted the creation date as a local
time, and applied the rollover to that. If the initial creation date
was around midnight local time, even a one hour change due to daylight
savings could result in Anki skipping or doubling up on a day. To
address this, the rollover is now applied to the current time instead
of the creation date.
The new code needs the current time passed into it. This makes it
easier to unit test, and for AnkiWeb to be able to use the user's local
timezone.
The new timezone code is currently disabled, as this code needs to be
ported to all clients before it can be activated.
