Currently, we use `assert` in RPC code to document logic and code assumptions. However, it seems a bit extreme to abort all of Bitcoin Core on an assert failure in one of the RPC threads. I suggest to replace all checks with a macro `THROW_LOGIC_ERROR_IF_ASSERT_FAILS(condition)` that does what it says. That logic error will then be returned to the rpc caller and will include instructions to report the error to our issue tracker.

Any objections or naming suggestions for that macro?
"\nA later preciousblock call can override the effect of an earlier one.\n"
                "\nThe effects of preciousblock are not retained across restarts.\n",
                {
                    {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "the hash of the block to mark as precious"},
                },
                RPCResults{},
                RPCExamples{
                    HelpExampleCli("preciousblock", "\"blockhash\"")
            + HelpExampleRpc("preciousblock", "\"blockhash\"")
                },
            }.Check(request);
    uint256 hash(ParseHashV(request.params[0], "blockhash"));
    CBlockIndex* pblockindex;
    {
        LOCK(cs_main);
        pblockindex = LookupBlockIndex(hash);
        if (!pblockindex) {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
        }
    }
    CValidationState state;
    PreciousBlock(state, Params(), pblockindex);
    if (!state.IsValid()) {
        throw JSONRPCError(RPC_DATABASE_ERROR, FormatStateMessage(state));
    }
    return NullUniValue;
}
static UniValue invalidateblock(const JSONRPCRequest& request)
{
            RPCHelpMan{"invalidateblock",