yang: serialization and config load broken for list with choice node

[alexandergall]

Schema snabb-pf-v1.yang

module snabb-pf-v1 {
  namespace snabb:pf-v1;
  prefix pf-v1;

  list foo {
    key "name";
    leaf name {
      type string;
    }
    choice bar {
      mandatory true;
      case case1 {
        leaf case1 {
          type string;
        }
      }
      case case2 {
        leaf case2 {
          type string;
        }
      }
    }
  }
}

Data pf-v1.cfg

foo {
  name "bar";
  case1 "baz";
}

setup.lua

local basic_apps = require("apps.basic.basic_apps")
local app_graph = require('core.config')

return function (conf)
   local graph = app_graph.new()
   app_graph.app(graph, "source", basic_apps.Source)
   app_graph.app(graph, "sink", basic_apps.Sink)
   app_graph.link(graph, "source.output -> sink.input")
   return {foo=graph}
end

schema.lua

local yang = require("lib.yang.yang")
local pf_schema = yang.add_schema_file("snabb-pf-v1.yang")
local config = yang.load_configuration("pf-v1.cfg", {  schema_name = "snabb-pf-v1" })

Writing the compiled configuration fails

$ sudo ./snabb snsh schema.lua
pf-v1.cfg: loading source configuration
pf-v1.cfg: error saving compiled configuration pf-v1.cfg.o: core/main.lua:26: assertion failed!

The error is hidden by a pcall. The actual failure occurs in

snabb/src/lib/yang/binary.lua

Line 111 in 771b55c

return assert(handlers[production.type])(production)

because there is no handler for a production of type choice.

There is another bug which may or may not be related. Run ptree with

$ sudo ./snabb ptree --name foo snabb-pf-v1.yang setup.lua pf-v1.cfg
pf-v1.cfg: loading source configuration
Warning: No assignable CPUs declared; leaving data-plane process without assigned CPU.
No CPUs available; not binding to any NUMA node.

Re-loading the same configuration fails

$ sudo ./snabb config load 7082 pf-v1.cfg
pf-v1.cfg: loading source configuration
pf-v1.cfg: error saving compiled configuration pf-v1.cfg.o: core/main.lua:26: assertion failed!
lib/yang/data.lua:514: missing choice value: bar

A workaround is to wrap the choice node in a container.