Unseal Wrap trait

[hgzimmerman]

Fixes #638.

The doc comments for the Wrap trait are not suitable for merging at the moment. Any feedback related to them would be appreciated.

[jxs]

Hi, thanks for getting this started!

[jxs]

can we give a detailed explanation of the trait, in the line of others like reply with a working example?

[hgzimmerman]

I'm struggling to come up with an example use case. Most existing uses of the Wrap trait use some sealed structure, so I'm not sure what would make sense to demonstrate here.

If the wrapper needs to implement FilterBase then unsealing Wrap doesn't open up a huge amount of flexibility.

[jxs]

it's getting nice! can you show where you are stalled? I think you can use BoxedFilter

[hgzimmerman]

I'm struggling to come up with a terse, but plausible use for Wrap. I look to something like warp::filters::log::Log or warp::filters::reply::WithHeader and see that their Wrap implementation is relying on private items. I don't think BoxedFilters will make this task easier for items that are like Log or WithHeader

The ultimate motivation behind me wanting to unseal this trait is to be able to implement something like what is detailed in this comment: #408 (comment), but I see that that also relies on other private items.

So its a problem of 1. I don't know what the example should demonstrate. and 2. I don't know if a plausible example could be created with the other "primitives" that are exposed currently.

[hgzimmerman]

Ok. So I finally figured out what you meant by using BoxedFilter.
I don't quite have it working yet due to some trait constraints, the errors of which should be present in the CI system, but I'll post the most notable ones here:

---- src/filter/wrap.rs - filter::wrap::Wrap (line 18) stdout ----
error[E0277]: the trait bound `<<F as warp::filter::FilterBase>::Extract as warp::generic::Tuple>::HList: warp::generic::Combine<_>` is not satisfied
##[error]  --> src/filter/wrap.rs:33:14
   |
18 |             .and(warp::any().map(|| log::info!("")))
   |              ^^^ the trait `warp::generic::Combine<_>` is not implemented for `<<F as warp::filter::FilterBase>::Extract as warp::generic::Tuple>::HList`

error[E0277]: the trait bound `std::convert::Infallible: warp::reject::sealed::CombineRejection<<F as warp::filter::FilterBase>::Error>` is not satisfied
##[error]  --> src/filter/wrap.rs:33:14
   |
18 |             .and(warp::any().map(|| log::info!("")))
   |              ^^^ the trait `warp::reject::sealed::CombineRejection<<F as warp::filter::FilterBase>::Error>` is not implemented for `std::convert::Infallible`

Any advice on where to go from here would be appreciated.

[jxs]

sorry for the late reply, and thanks for your effort! yeah this solution seems it would always need to unseal other traits which would lead to more confusion, and in the end even if it worked one would always need to impl Wrap and probably Future which would not be the way one works with Filters.
I have since posted an update on #16 (comment) can you give your opinion there?
Thanks

[hgzimmerman]

Should this PR be closed in favor of your wrap_fn proposal?

[hgzimmerman]

Is there anything I can do to assist in getting your wrap_fn included into Warp?

[jxs]

@hgzimmerman yeah we can close this one in favor of the wrap_fn proposal, which i am awaiting for feedback on the issue.
Thanks