Special reducers don't preserve user-defined names

[RReverser]

As per recent API revamp proposal, special reducers attached to init/client_connected/client_disconnected events should preserve user-provided names and use the V9 moduledef out-of-band signal to indicate the lifecycle event it's attached to.

I'm working on the C# counterpart of this (V8 -> V9 migration), but I noticed that Rust implementation of the bindings macro, which already supports V9 moduledef, doesn't preserve the reducer names either.

cc @gefjon

[bfops]

Adding this to 1.0 release since it was created recently.

[bfops]

This is technically ABI-breaking because this could hypothetically create naming conflicts in the module and/or generated code, but only in cases where users are being silly. (And users can address by fixing it in their module code).

[cloutiertyler]

This is actually a P1 because it causes the host to not call lifecycle reducers on the C# modules unless they share the name of the reducer. This is because the module host is incorrectly implemented and is still calling lifecycles based on their names and not on their V9 flags.

The only reason the Rust is working now is because the Rust macros in the module library rewrite the names of lifecycle reducers to the names that the module host (incorrectly) expects.

[kazimuth]

https://github.com/clockworklabs/SpacetimeDB/blob/master/crates/schema/src/def.rs#L903 is where the data is stored in the ModuleDef. There's a ModuleDef stored in the modulehost that you can query to get this information. You could also cache the names of the lifecycle reducers on ModuleDef construction; ModuleDef is an ephemeral in-memory data structure so changes to it are not breaking.