transport json node format

[marceloleitner]

http://neat.readthedocs.io/en/latest/properties.html#transport specifies that transport is of type Array.
The Tutorial at http://neat.readthedocs.io/en/latest/tutorial.html#a-minimal-client uses an array of transports. But that array doesn't work for at least two reasons:

• An assert ensuring that transport node has an object named value fires off. This allows it to go on, while still handling the WebRTC case:

@@ -819,8 +819,7 @@ neat_set_property(neat_ctx *ctx, neat_flow *flow, const char *properties)
         json_object_foreach(props, key, prop) {
             if (strcmp(key, "transport") == 0) {
                 val = json_object_get(prop, "value");
-                assert(val);
-                if (json_typeof(val) == JSON_STRING) {
+                if (val && json_typeof(val) == JSON_STRING) {
                     if (strcmp(json_string_value(val), "WEBRTC") == 0) {
                         flow->webrtcEnabled = true;

• Later on, the validation of the transport object rejects it too, because it is of type JSON_ARRAY and that doesn't match the check on:

nt_find_enabled_stacks()
{
...
    if (json_is_object(transports)) {   <--- false
...
    } else  {
        fprintf(stderr, "ERROR: Invalid property format\n");
    }

Output of a debug session:

Breakpoint 1, nt_find_enabled_stacks (json=0x60a9b0, stacks=stacks@entry=0x7fffffffccc0,
    stack_count=stack_count@entry=0x7fffffffccb8, precedences=precedences@entry=0x0)
    at /usr/src/debug/libneat-0.0.1~td161-1.x86_64/neat_json_helpers.c:72
72      {
Missing separate debuginfos, use: dnf debuginfo-install jansson-2.11-1.fc27.x86_64 ldns-1.7.0-11.fc27.x86_64 libmnl-1.0.4-4.fc27.x86_64 libuv-1.19.2-1.fc27.x86_64 lksctp-tools-1.0.16-8.fc27.x86_64 openssl-libs-1.1.0h-3.fc27.x86_64 zlib-1.2.11-4.fc27.x86_64
(gdb) list
67       * TODO: Contemplate whether this can be written better somehow.
68       */
69      void
70      nt_find_enabled_stacks(json_t *json, neat_protocol_stack_type *stacks,
71                          size_t *stack_count, int *precedences)
72      {
73          json_t *transports, *transport;
74          json_error_t error;
75          size_t i;
76          neat_protocol_stack_type *stack_ptr = stacks;
(gdb) step
84          assert(json);
(gdb)
85          assert(stacks && stack_count);
(gdb)
88          transports = json_object_get(json, "transport");
(gdb)
89          if (transports == NULL) {
(gdb) p *transports
$1 = {type = JSON_ARRAY, refcount = 1}
(gdb) step
99          if (json_is_object(transports)) {
(gdb)
141             fprintf(stderr, "ERROR: Invalid property format\n");

Which made me wonder if the format used in the Tutorial is actually valid.
There is https://github.com/NEAT-project/neat/blob/master/examples/prop_all.json which also uses an array but it is not used by any example. The contents looks reasonable.

[EPS87]

@marceloleitner
Sounds very reasonable we should try it