moved all code into sealed:: mod to make API tagging possible

[milyin]

The whole zenoh library API is present in lib.rs file with "pub use" reexports. No file mods are public.

This allows to overview all the API from single file. But this works one direction only. I.e. structure/trait/function belongs to API if it's declared in public module in lib.rs. But it's impossible to say is some structure/function/method public by just looking at it's definition itself. Even if it's pub(crate) it still can be reexported by lib.rs.

This may cause inconveniences when reading code. Also, which is more important, this breaks logic of tagging tool https://github.com/zettaScaleLabs/api-matrix. It needs explicit pub declarations for interface items, so the fact that pub(crate) instances still can be part of interface makes it's diagnostics incorrect.

This update removes pub(crate) statements replacing them to pub(in crate::sealed). Unlike pub(crate) the pub(in crate::sealed) can't be reexported because the lib.rs don't have access to them. This forces us to explicitly mark all interface elements as pub. I.e. if something belongs to API it should be both reexported in lib.rs and marked as pub in the source.

The usage of pub(crate) should be avoided as this doesn't explicitly state if item belongs to API or not.

[milyin]

here pub(crate) (or better pub(self)?) should be restored: these namespaces are technical, they are not part of public API

[milyin]

Joseph — Today at 10:43 AM
I've tried to replace pub KeyExpr by pub(crate) KeyExpr, and I got
error[E0364]: KeyExpr is only public within the crate, and cannot be re-exported outside

So I admit I don't understand the issue you try to solve
See https://doc.rust-lang.org/error_codes/E0364.html

Michael Ilyin — Today at 11:27 AM
Yes, you are right. I can publicly reexport from "pub(crate)" mods but not the "pub(crate)" instances itself. Then yes, the problem doesn't exists, the PR is unnecessary