Misleading ILPP error message when [Rpc] is used inside a local function

[GitUser187]

Description

When I put the [Rpc] attribute on top of a local function (for example, inside the Update function), this error message appears: "Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP: Assets\Scripts\Script.cs(x,x): error - Rpc method must end with 'Rpc' suffix!". This is quite confusing as the function does in fact end with the Rpc suffix. It seems the ILPP is checking the compiler-generated name for local functions (like g__SomethingRpc|0_0), which no longer ends with "Rpc"

Reproduce Steps

1. Create a NetworkBehaviour class
2. Inside Update(), define a local function named SomethingRpc
3. Add the [Rpc] attribute
4. Let it compile
5. Observe the confusing error message

Expected Outcome

A more concise error message which specifies that you mustn't have Rpcs be local functions or just the ability to have Rpcs be local functions

Environment

NGO 2.5.0

[NoelStephensUnity]

@GitUser187

Ahh... I think that is a lack of documentation regarding local functions and RPCs as well as we need to detect when trying to use a local function as an RPC. I did a quick pass in the ILPP side and have it logging these two error messages:

It still logs the error about it being static (which in reality that is what you are doing when you create a local function that can only be accessed by the function it is defined within):

PostProcessing failed: Unity.ILPP.Runner.ILPostProcessorDiagnosticsException: Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP: Assets\Scripts\NetworkTransformWithLogs.cs(229,9): error - RPC method must not be static!

Then it logs this additional error message if it determines it is most likely a local function:

Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP: Assets\Scripts\NetworkTransformWithLogs.cs(229,9): error - g__LocalFunctionRpc|20_0 appears to be a local function. Local functions cannot be RPCs.

So... local functions are not supported... but we also don't give you any meaningful error nor do we call this out clearly in our RPC documentation. Both of which should be updated to prevent this kind of confusion.

Thank you for bringing this to our attention!

Recommended Solution

The recommended solution (which I am pretty sure you figured out) is to just keep RPCs at the class level scope and assure the function itself is not static. If you copy and paste that function into the class itself...then it will no longer throw that error message and start working.