[contracts] API host functions: remove seal_ name prefix + enable aliasing

[agryaznov]

Resolves #11444

• Added #[prefixed_alias] to the #[define_env] proc attribute macro.

  For a host_fn() marked by the attribute, the macro creates an additional alias function seal_host_fn() which is exactly the same as the original one but has the prefixed name for backwards compatibility. See this comment for a usage example.

• Renamed API functions + added aliases.

• Updated tests and benchmarks.

[athei]

• Rustdocs need to be updated with the new attribute
• No non-prefixed version of an aliased function is used in any test

Bonus: Make the alias call the non-aliased function instead of duplicating the body.

[agryaznov]

• Rustdocs need to be updated with the new attribute

They are updated for the macro thing. Or are there any other places I forgot about?

• No non-prefixed version of an aliased function is used in any test

Not exactly. For now, all tests for __unstable__ functions use non-prefixed version, as they will eventually become stabilized and get used by users with the new naming. For all other tests prefixed functions left because they are the ones used by pallet_contract users.

Bonus: Make the alias call the non-aliased function instead of duplicating the body.

Not realistic in current design. See e.g. how gas host fn gets expanded by the macro:

       fn impls<F: FnMut(&[u8], &[u8], crate::wasm::env_def::HostFunc<E>)>(f: &mut F) {
            f("seal0".as_bytes(), "gas".as_bytes(), {
                fn gas<E: Ext>(
                    ctx: &mut crate::wasm::Runtime<E>,
                    args: &[sp_sandbox::Value],
                ) -> Result<sp_sandbox::ReturnValue, sp_sandbox::HostError>
                where
                    <E::T as frame_system::Config>::AccountId: sp_core::crypto::UncheckedFrom<<E::T as frame_system::Config>::Hash>
                        + AsRef<[u8]>,
                {
                    #[allow(unused)]
                    let mut args = args.iter();
                    let mut body = || {
                        let amount : < u32 as crate :: wasm :: env_def :: ConvertibleToWasm > :: NativeType = args . next () . and_then (| v | < u32 as crate :: wasm :: env_def :: ConvertibleToWasm > :: from_typed_value (v . clone ())) . expect ("precondition: all imports should be checked against the signatures of corresponding
                                functions defined by `#[define_env]` proc macro by the user of the macro;
                                thus this can never be `None`;
                                qed;") ;
                        {
                            ctx.charge_gas(RuntimeCosts::MeteringBlock(amount))?;
                            Ok(())
                        }
                    };
                    body().map_err(|reason| {
                        ctx.set_trap_reason(reason);
                        sp_sandbox::HostError
                    })?;
                    return Ok(sp_sandbox::ReturnValue::Unit);
                }
                gas::<E>
            });
...

So basically each host fn becomes visible only inside a block which is a closure parameter. We can't call them from within each other.

[athei]

They are updated for the macro thing. Or are there any other places I forgot about?

No. I was just too stupid to scroll down. The docs are great.

Not exactly. For now, all tests for unstable functions use non-prefixed version, as they will eventually become stabilized and get used by users with the new naming. For all other tests prefixed functions left because they are the ones used by pallet_contract users.

But only for the function which don't use the new attribute. So there is no code which tests whether the new prefix leaves generates version.

[agryaznov]

But only for the function which don't use the new attribute. So there is no code which tests whether the new prefix leaves generates version.

I've added a test which catches this case.

[athei]

I think your changes broke the build.

[agryaznov]

Yeah, making examples no-run in macro docs was not a good idea. It is a tricky puzzle to make it compile with rustdoc (at least no one of frame_support_procedural doc examples are intended to really compile).

[agryaznov]

Added prefixes for the unstable host functions versions. Otherwise we break in-progress PR in ink!. We will remove the alias once we stabilize.

[athei]

Thanks :)

[ascjones]

LGTM!

[agryaznov]

bot merge