Fix passing of empty string arg to riak rpc in riak admin services

[hmmr]

This should fix #8.

[martinsumner]

Changing the rpc() function for the case where there are no args beyond the function would work as well ...

i.e.

rpc() {
    local mod=$1
    local fun=$2
    shift 2
    if [ $# -gt 0 ]; then
        "${PLATFORM_BIN_DIR}/riak" rpc $mod $fun `fmt "$@"`
    else
        "${PLATFORM_BIN_DIR}/riak" rpc $mod $fun "[[]]"
    fi
}

rpc() {
    local mod=$1
    local fun=$2
    shift 2
    if [ $# -gt 0 ]; then
        "${PLATFORM_BIN_DIR}/riak" rpc $mod $fun `fmt "$@"`
    else
        "${PLATFORM_BIN_DIR}/riak" rpc $mod $fun "$3"
    fi
}

But do we fear that this will simply cause something else to fail?

[hmmr]

Indeed, replacing "[[]]" with "$3" will break commands such as riak admin reformat-indexes, for which an explicit [] is required as the underlying riak_kv_console:reformat_indexes is /1. Without that, rebar machinery will try to invoke riak rpc with two arguments, and result in a call to riak_kv_console:reformat_indexes/0:

$ ./rel/riak/bin/riak admin reformat-indexes
RPC to '[email protected]' failed: {'EXIT',
                                 {undef,
                                  [{riak_kv_console,reformat_indexes,[],[]}]}}

On the other hand, riak_core_node_watcher:servives is arity 0, and for this case, "" (and not "[[]]") is appropriate.

There was a change in argument passing conventions in rebar-3.18. Exactly how it all worked before, is a good question.

So yes, replacing rpc with rpc_raw for riak admin services is the minimal sufficient change.

[martinsumner]

Thanks for the explanation.

Going forward we need to get this into openriak-3.2 and openriak-3.4 branches. There's a team call on Wednesday, we can use this change as a test case as to how we agree changes on those branches.

Heads up @tburghart