If I make a writeRelationships call with more than one precondition, is there a reliable way to determine which precondition failed? The exception message contains the text of the failing precondition - but I'm hoping to find the index of the failing precondition, and can't see how to access this.

it should be possible, yes.. The gRPC error returns rich metadata including the precondition that failed. It does not give you the index, but it gives you the whole precondition definition: https://github.com/authzed/spicedb/blob/e8aeca080d7804e0fb1782c675065c7d5f020937/internal/services/v1/errors.go#L165-L226

Oh, cool - I thought I'd have to programmatically parse the text of the error message to correlate it to the preconditions I passed into the call.

I don't know how to do this with Java, but first entry in google seemed promising: https://stackoverflow.com/questions/60936054/how-to-use-grpc-status-details-in-package-io-grpc

Thanks for the hint! I'm not super familiar with grpc - so didn't know where to start. For future searchers of truth, roughly what you need to do is (kotlin)

} catch (e: StatusRuntimeException) {
    if (e.status.code == Code.FAILED_PRECONDITION) {
        val statusProto = io.grpc.protobuf.StatusProto.fromStatusAndTrailers(e.status, e.trailers)
        val errorInfo = statusProto.getDetails(0).unpack(com.google.rpc.ErrorInfo::class.java)
        val preconditionFailureDetails = errorInfo.metadataMap

I think there should also be types generated for the errors in the SDK, since it's defined as part of the proto API

Yep - there's an enum

ErrorReasonOuterClass.ErrorReason

- but can't see a custom type (or key constants) for the data in the metadataMap. which is ok - it's fine to work with.

yeah so far this feels like the most cumbersome and frustrating part of the java gRPC API