This patch should ideally be split into multiple smaller ones, but life
is life.
This main purpose of this patch is to fix and to test
`SlidingSyncListRequestGenerator`. This quest has led me to rename
mutiple fields in `SlidingSyncList` and `SlidingSyncListBuilder`, like:
* `rooms_count` becomes `maximum_number_of_rooms`, it's not something
the _client_ counts, but it's a maximum number given by the server,
* `batch_size` becomes `full_sync_batch_size`, so that now, it
emphasizes that it's about full-sync only,
* `limit` becomes `full_sync_maximum_number_of_rooms_to_fetch`, so that
now, it also emphasizes that it's about ful-sync only _and_ what the
limit is about!
This quest has continued with the renaming of the `SlidingSyncMode`
variants. After a discussion with the ElementX team, we've agreed on the
following renamings:
* `Cold` becomes `NotLoaded`,
* `Preload` becomes `Preloaded`,
* `CatchingUp` becomes `PartiallyLoaded`,
* `Live` becomes `FullyLoaded`.
Finally, _le plat de résistance_.
In `SlidingSyncListRequestGenerator`, the `make_request_for_ranges`
has been renamed to `build_request` and no longer takes a `&mut self`
but a simpler `&self`! It didn't make sense to me that something
that make/build a request was modifying `Self`. Because the type of
`SlidingSyncListRequestGenerator::ranges` has changed, all ranges now
have a consistent type (within this module at least). Consequently, this
method no longer need to do a type conversion.
Still on the same type, the `update_state` method is much more
documented, and errors on range bounds (offset by 1) are now all fixed.
The creation of new ranges happens in a new dedicated pure function,
`create_range`. It returns an `Option` because it's possible to not be
able to compute a range (previously, invalid ranges were considered
valid). It's used in the `Iterator` implementation. This `Iterator`
implementation contains a liiiittle bit more code, but at least now
we understand what it does, and it's clear what `range_start` and
`desired_size` we calculate. By the way, the `prefetch_request` method
has been removed: it's not a prefetch, it's a regular request; it was
calculating the range. But now there is `create_range`, and since it's
pure, we can unit test it!
_Pour le dessert_, this patch adds multiple tests. It is now
possible because of the previous refactoring. First off, we test the
`create_range` in many configurations. It's pretty clear to understand,
and since it's core to `SlidingSyncListRequestGenerator`, I'm pretty
happy with how it ends. Second, we test paging-, growing- and selective-
mode with a new macro: `assert_request_and_response`, which allows to
“send” requests, and to “receive” responses. The design of `SlidingSync`
allows to mimic requests and responses, that's great. We don't really
care about the responses here, but we care about the requests' `ranges`,
and the `SlidingSyncList.state` after a response is received. It also
helps to see how ranges behaves when the state is `PartiallyLoaded`
or `FullyLoaded`.
Ivan Enderlin
Jonas Platte