NBJSONRPC002: Colliding wire method names

Property	Value
ID	NBJSONRPC002
Category	Usage
Default severity	Warning

Two methods on an interface annotated with JsonRpcContractAttribute or RpcMarshalableAttribute map to the same JSON-RPC method name under the default naming policy. Inherited methods are included. Distinct declarations on unrelated base interfaces remain distinct, even when their CLR signatures match; diamond inheritance of the same declaration is counted only once. Non-public helpers are excluded unless explicitly included with MethodShapeAttribute, and methods marked with Ignore are excluded. The diagnostic identifies the conflicting member, or the derived contract when the conflicting member is inherited.

Why this is reported

The default naming policy removes a trailing Async suffix and lowercases the first character. Names explicitly assigned with Name are compared verbatim and are not transformed. Wire names are case-sensitive.

Nerdbank.JsonRpc does not resolve method overloads. Different parameter counts, parameter types, optional arguments, or cancellation tokens do not disambiguate methods with the same wire name. Registering such a target throws InvalidOperationException. A client proxy can send both calls, but cannot make the receiving target distinguish them.

Example

Both methods below use displayMessage on the wire, even though one has an extra argument:

[JsonRpcContract(GenerateProxy = false)]
public interface ICollidingBackchannel
{
    [MethodShape(Name = "displayMessage")]
    Task DisplayMessageWithActionsAsync(string message, string[] actions);

    Task DisplayMessageAsync(string message);
}

Assign distinct explicit names, or rename the methods so their convention-derived names differ:

[JsonRpcContract]
[GenerateShape(IncludeMethods = MethodShapeFlags.PublicInstance)]
public partial interface IBackchannel
{
    [MethodShape(Name = "displayMessageWithActions")]
    Task DisplayMessageWithActionsAsync(string message, string[] actions);

    Task DisplayMessageAsync(string message);
}

Changing a wire name changes the protocol. Coordinate the change between independently deployed clients and servers.

Custom naming and suppression

This rule assumes Default. Arbitrary delegates assigned to MethodNameTransform or MethodNameTransform cannot be evaluated by the analyzer. Suppress this warning locally only when a custom naming policy makes the names distinct, and configure both peers consistently. The rule remains active when JsonRpcContractAttribute.GenerateProxy is false. No automatic code fix is offered because selecting a wire name is a protocol design decision.